Inflammatory Bowel Disease and Cardiovascular Risk

FACULTY OF HEALTH AND MEDICAL SCIENCES UNIVERSITY OF COPENHAGEN

PhD Thesis Søren Lund Kristensen

Inflammatory Bowel Disease and Cardiovascular Risk Epidemiological Studies

Gentofte Hospital, University of Copenhagen Department of Cardiology

Submitted March 2014

Inflammatory Bowel Disease and Cardiovascular Risk Epidemiological Studies PhD Thesis - Søren Lund Kristensen, MD Public defense: Gentofte Hospital, 13th June, 2014

This thesis has been submitted to the Graduate School of The Faculty of Health and Medical Sciences, University of Copenhagen

Faculty supervisor Peter Riis Hansen, MD, PhD, DMSc Project supervisor Gunnar Hilmar Gislason, MD, PhD Additional supervisors Christian Torp-Pedersen, MD, DMSc Ole Haagen Nielsen, MD, DMSc

Members of the assessment committee: Jesper Hastrup Svendsen, MD, PhD, DMSc (Chairperson) Tina Jess, MD, PhD, DMSc Matthew Grainge, BSc, MSc, PhD

Correspondence to: Søren Lund Kristensen, MD Department of Cardiology Gentofte Hospital, University of Copenhagen Niels Andersens Vej 65, Post 635 2900 Hellerup, Copenhagen, Denmark E-mail: [email protected]

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Contents PREFACE ................................................................................................................... 4 ABBREVIATIONS ....................................................................................................... 6 PAPERS...................................................................................................................... 7 SUMMARY .................................................................................................................. 8 DANSK RESUMÉ ..................................................................................................... 10 BACKGROUND ........................................................................................................ 12 Inflammatory bowel disease ............................................................................................................................. 12 Extraintestinal manifestations of IBD ............................................................................................................... 13 Inflammation in IBD......................................................................................................................................... 14 Inflammation in cardiovascular disease ............................................................................................................ 14 Common features in the pathogenesis of IBD and cardiovascular disease ....................................................... 15 IBD pharmacotherapy in relation to cardiovascular disease ............................................................................. 16 Objectives ......................................................................................................................................................... 17

METHODS ................................................................................................................ 17 Databases .......................................................................................................................................................... 17 Study design ......................................................................................................................................................... 18 Identification of subjects with IBD ................................................................................................................... 18 Cohorts ............................................................................................................................................................. 19 IBD disease activity .......................................................................................................................................... 20 Outcome predictors ........................................................................................................................................... 20 Ethics .................................................................................................................................................................... 21 Statistical analyses ............................................................................................................................................... 21

RESULTS.................................................................................................................. 25 Paper I: Increased risk of MI, stroke and cardiovascular death ........................................................................ 25 Paper II: Increased risk of AF and stroke ......................................................................................................... 27

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Paper III: Risk of hospitalization for heart failure in patients with IBD ........................................................... 29 Paper IV: Prognosis after first-time MI ............................................................................................................ 30

DISCUSSION ............................................................................................................ 32 Comparison to findings in other studies ............................................................................................................ 32 MI, stroke and cardiovascular death ................................................................................................................. 32 AF and stroke .................................................................................................................................................... 33 Heart failure ...................................................................................................................................................... 34 Post MI prognosis ............................................................................................................................................. 34 Methodological considerations ........................................................................................................................... 35 General Considerations ..................................................................................................................................... 35 Confounding factors ......................................................................................................................................... 36 Matching versus nationwide cohort study design ............................................................................................. 37 IBD exposure and disease activity .................................................................................................................... 38 Outcomes .......................................................................................................................................................... 39 Conclusions .......................................................................................................................................................... 40 Clinical implications and future research ......................................................................................................... 40

REFERENCES .......................................................................................................... 41 APPENDICES ........................................................................................................... 48 Supplementary tables ........................................................................................................................................ 48 Appendix I (Paper I) ......................................................................................................................................... 50 Appendix II (Paper II) ...................................................................................................................................... 50 Appendix III (Paper III) .................................................................................................................................... 50 Appendix IV (Paper IV) ................................................................................................................................... 50

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Preface My interest in cardiology and research evolved during my internship at Nykøbing Falster Hospital in the spring of 2010. There, I met Jakob Raunsø, then a PhD student at Gentofte Hospital, who referred me to his supervisor Gunnar Gislason. Gunnar quickly involved me in a project started by Emil Fosbøll on NSAIDs and kidney function, and I gradually started research alongside my clinical work. Upon finishing this paper, Gunnar introduced me to Peter Riis Hansen who suggested the idea of a PhD thesis on inflammatory bowel disease and cardiovascular risk. Peter had a clear outline for the project, and had previously successfully supervised related projects on psoriasis and rheumatoid arthritis. These factors combined made it an easy choice for me to embark on the project.

Peter is a knowing and enthusiastic supervisor who provides prompt and in-depth guidance when needed. I am grateful for the hard work he has put into this project, and I have learned a lot from the high standards he demands. Gunnar taught me the statistical programming, and handling of large datasets essential for this type of research — but he also had to listen to and absorb my various complaints and frustrations with funding, reviews etc. I owe Gunnar great thanks for the completion of this PhD. Christian Torp-Pedersen has been a great help in deciding the overall objectives and methods of this thesis and I am a great admirer of his drive, straightforwardness and unique approach to quickly identify and communicate strengths and weaknesses in a project. Ole Haagen Nielsen has provided a refreshing “non-cardiology” perspective, and been very important in defining some of the fundamental assumptions on which this PhD is based. I also wish to thank Ole Ahlehoff, Jesper Lindhardsen and Rune Erichsen for their assistance and good discussions about study design and epidemiological issues.

Another important ingredient in my work with this PhD thesis has been the atmosphere and colleagues from my daily life in the research department in Gentofte. I have met a number of inspiring people and many with whom I hope to maintain a friendship that goes beyond mere research. A three-week course in Florence in the summer of 2011 fostered a close relationship in the group, which has been invaluable for me, especially in times where completing this PhD thesis seemed a distant prospect. The Department of Cardiology at Gentofte Hospital has a rare and strong focus on research, facilitated by Jan Kyst Madsen and now Jan Skov Jensen and I owe many thanks 4

for the departments’ funds to get this project started. Further, I would like to thank Gunnar V. Jensen, head of the Department of Cardiology at Roskilde Hospital for funding my project for three months in the summer of 2012, and P. Carl Petersens Fond who entrusted me a one-year grant in the spring of 2013. These contributions have been critical for the completion of this PhD thesis. I would also like to thank my friends and colleagues Christian Selmer and Morten Lamberts for extensive feedback and valuable comments when writing this thesis.

Finally yet importantly, I would like to thank my family, who has gone through some hard times the last few years, and my dear girlfriend Julie. You give me a lot of love and remind me that there´s more to life than work, and I feel fortunate to share my life with you.

Søren, March 2014

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Abbreviations AF

Atrial fibrillation

ATC

Anatomical Therapeutical Chemical Classification

CD

Crohn’s disease

CI

Confidence interval

COPD

Chronic obstructive pulmonary disease

CRP

C-reactive protein

HF

Heart failure

HR

Hazard ratio

IBD

Inflammatory bowel disease

ICD

International Classification of Diseases

IR/IRR

Incidence rate/Incidence rate ratio

MI

Myocardial infarction

OR

Odds ratio

PY

Person-years

RCT

Randomized clinical trial

Th

T helper cells

TNF

Tumor necrosis factor alpha

UC

Ulcerative colitis

VTE

Venous thromboembolic disease

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Papers This thesis is based on research carried out during my time as a PhD student at the department of Cardiology, Gentofte Hospital, affiliated with the Graduate School of Health and Medical Sciences, University of Copenhagen. It includes four original papers (Appendices I-IV):

I.

Disease activity in inflammatory bowel disease is associated with increased risk of myocardial infarction, stroke and cardiovascular death – a Danish nationwide cohort study. Kristensen SL, Ahlehoff O, Lindhardsen J, Erichsen R, Jensen GV, Torp-Pedersen C, Nielsen OH, Gislason GH, Hansen PR. PLoS One. 2013. 2013;8(2) doi: 10.1371/journal.pone.0056944

II.

Increased risk of atrial fibrillation and stroke during active stages of inflammatory bowel disease: a nationwide study. Kristensen SL, Lindhardsen J, Ahlehoff O Erichsen R, Lamberts M, Khalid U, TorpPedersen C, Nielsen OH, Gislason GH, Hansen PR. Europace. 2013. doi: 10.1093/europace/eut312

III.

Inflammatory bowel disease is associated with an increased risk of hospitalization for heart failure: a Danish nationwide cohort study. Kristensen SL, Ahlehoff O, Lindhardsen J, Erichsen R, Lamberts M, Khalid U, TorpPedersen C, Nielsen OH, Gislason GH, Hansen PR. Submitted 2014.

IV.

Prognosis after first-time myocardial infarction in patients with inflammatory bowel disease according to disease activity: a nationwide cohort study. Kristensen SL, Ahlehoff O, Lindhardsen J, Erichsen R, Lamberts M, Khalid U, TorpPedersen C, Nielsen OH, Gislason GH, Hansen PR. Submitted 2014

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Summary The immune system plays a pivotal role in the development and progression of cardiovascular disease, and inflammatory activation is an important factor in atherosclerosis, and arterial- and venous thrombosis. These insights have raised concerns that patients with chronic inflammatory diseases, including inflammatory bowel disease (IBD), are at increased risk of developing cardiovascular disease. Other chronic inflammatory conditions, such as rheumatoid arthritis, psoriasis, coeliac disease and systemic lupus erythematosus, have all been linked with an increased risk of cardiovascular disease, whereas data on the cardiovascular risk in IBD are sparse. Ulcerative colitis and Crohn’s disease are the main entities of IBD. They are distinguished by differences in anatomic location, clinical and histological features. Importantly, they also share a number of common characteristics, including chronic intestinal inflammation, and a clinical course with periods of remission succeeded by relapsing flares. A link between IBD and increased risk of cardiovascular disease could potentially be of major public health impact as IBD affects a relatively young population with an estimated prevalence of 2.2 million persons in Europe alone.

This thesis is based on data derived from individual-level linkage across the Danish nationwide registries including the Danish Civil Registration system, the National Patient Registry, the Registry of Medicinal Product Registry (national prescription registry), and the Danish Registry on Causes of Death. The objectives were to investigate if IBD was associated with an increased risk of cardiovascular events, i.e. myocardial infarction, stroke, atrial fibrillation, and heart failure when compared to the background population. More specifically, we wanted to examine whether a potential IBD-associated risk was related to IBD activity identified by predefined criteria. In addition, we aimed to evaluate whether IBD affected prognosis in a population of patients with first-time myocardial infarction.

The investigations were driven by the following hypotheses: 1.

IBD is associated with an increased risk of myocardial infarction, stroke, atrial

fibrillation, and heart failure. 2.

The risk of adverse cardiovascular events in IBD patients is related to phases of active

disease. 3.

IBD is associated with worsened prognosis after a first-time myocardial infarction. 8

The main results were a significant association between IBD and increased risk of myocardial infarction and stroke. Further, we found novel evidence of increased incidence of atrial fibrillation and heart failure in patients with IBD. Additionally, we demonstrated that coexistent IBD at time of a first myocardial infarction was associated with a worsened prognosis. Perhaps most interesting, we found that that the risk for all endpoints was markedly increased and often more than doubled during active disease stages, whereas the incidence during quiescent stages was comparable to the risk in the background population. Among patients with a first-time myocardial infarction, flares of IBD was associated with a considerably increased risk of major adverse events and recurrent myocardial infarction.

In conclusion, IBD was associated with an increased risk of cardiovascular disease, and this risk was strongly linked to active disease, whereas no increased risk was present when IBD was quiescent. These findings are in line with observations from other chronic inflammatory conditions, including rheumatoid arthritis. The observational nature of these studies limits our ability to draw conclusions in terms of what caused the increased risk, but the high risk at active disease suggests a role for inflammatory mechanisms. Thus, our studies indicate that efficient treatment of IBD aimed at minimizing length and number of disease activity episodes combined with clinical surveillance and, if relevant, cardioprotective treatment may reduce cardiovascular risk in these patients.

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Dansk resumé Immunsystemet spiller en central rolle i udviklingen af hjertekarsygdom, og inflammatoriske (betændelses-) mekanismer er af afgørende betydning i udviklingen af aterosklerose (åreforkalkning). Andre sygdomme karakteriseret ved kronisk inflammation, såsom leddegigt, psoriasis, cøliaki og systemisk lupus erythematosus, er alle blevet forbundet med en øget risiko for hjertekarsygdom, hvorimod risikoen hos patienter med inflammatorisk tarmsygdom er usikker. Disse patienter har en øget risiko for venøs trombotisk sygdom (dyb venetrombose og blodprop i lungen), hvorimod risikoen for arteriel hjertekarsygdom - herunder blodprop i hjerte og hjerne - er uklar på grund af et begrænset antal studier med modstridende resultater.

Inflammatorisk tarmsygdom er kendetegnet ved en kronisk betændelsestilstand i tarmen. Gruppen omfatter en bred vifte af sygdomme, hvoraf de to hyppigste er colitis ulcerosa og Crohns sygdom. De to lidelser adskiller sig på anatomisk udbredelse, histologiske egenskaber, og kliniske symptomer, men har også mange ligheder, bl.a. er de begge karakteriseret ved kronisk inflammation i tarmen, og et klinisk forløb med rolige faser afløst af periodisk opblussen. Omkring 30.000 personer i Danmark og 2,2 mio. i Europa lider af inflammatorisk tarmsygdom, og derfor har det stor folkesundhedsmæssig betydning, såfremt inflammatorisk tarmsygdom er forbundet med øget risiko for hjertekarsygdom.

Denne ph.d.-afhandling er baseret på data indhentet via kobling af informationer fra de nationale danske registre, herunder Landspatientregistret, Lægemiddelregistret, Dødsårsagsregistret og Det Centrale Personregister. Formålet med afhandlingen var at undersøge hvorvidt inflammatorisk tarmsygdom var forbundet med en øget risiko for at udvikle hjertekarsygdom. Ydermere ville vi undersøge om en potentielt øget risiko var relateret til perioder med aktivitet i tarmsygdommen, og dermed også til inflammatorisk aktivering. Ved hjælp af prædefinerede aktivitetskriterier for tarmsygdommen identificerede vi formodede højrisikoperioder med aktiv sygdom, og perioder, hvor tarmsygdommen var i ro.

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Vi havde følgende hypoteser: 1.

Inflammatorisk tarmsygdom er forbundet med en øget risiko for blodprop i hjerte og

hjerne, atrieflimren, hjertesvigt, og død forårsaget af hjertekarsygdom. 2.

Risikoen for hjertekarsygdom er særlig høj i perioder med opblussen og vedvarende

aktivitet i tarmsygdommen. 3.

Prognose efter blodprop i hjertet er forringet hos patienter med inflammatorisk

tarmsygdom. Hovedresultaterne var påvisningen af en øget forekomst af blodprop i hjerte og hjerne, atrieflimren og hjertesvigt hos patienter med inflammatorisk tarmsygdom sammenlignet med baggrundsbefolkningen. Ved blodprop i hjertet havde patienter med inflammatorisk tarmsygdom øget risiko for at dø, både under indlæggelsen men også i den efterfølgende periode. En særlig vigtig observation var at risikoen for hjertekarsygdom typisk var mere end fordoblet i perioder med aktiv inflammatorisk tarmsygdom, hvorimod risikoen i perioder med ro i tarmsygdommen var sammenlignelig med risikoen hos baggrundsbefolkningen.

Inflammatorisk tarmsygdom var således associeret med en øget risiko for et bredt spektrum af kardiovaskulære lidelser, og denne risiko var langt overvejende til stede i perioder med aktiv inflammatorisk tarmsygdom. Selvom den observationelle natur af studierne gør at vi ikke kan påvise årsagssammenhænge, antyder observationen af høj risiko i perioder med aktiv tarmsygdom, at der er en sammenhæng med graden af inflammation. Det kan dog ikke udelukkes at den farmakologiske behandling i disse perioder kan have haft betydning. Det bør således undersøges nærmere, om øget fokus på tidlig behandling af opblussen og forebyggende behandling af hjertekarsygdomme og kendte risikofaktorer kan nedbringe dødeligheden.

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Background Inflammatory bowel disease Inflammatory bowel disease (IBD) is a group of chronic inflammatory conditions of the colon and small intestine, of which Crohn’s disease (CD) and ulcerative colitis (UC) are the two main entities.1-3 CD and UC are relapsing systemic inflammatory diseases, with CD potentially affecting any part of the gastrointestinal tract, whereas UC is limited to the colon.1, 2, 4 Clinical presentations of IBD include abdominal pain, diarrhea, rectal bleeding, blood or mucus in stool, and tenesmus, with fever and other more generalized symptoms (e.g. malaise and weight loss) being more common in CD.1, 3 In clinical practice, distinction between CD and UC can be difficult, and is often based on differences in endoscopic and histological features.

IBD is characterized by interchanging phases of remission and relapses with flares, although there is diversity in the natural history of UC and CD. In a cohort of UC patients, 50% of patients remained in remission or had only mild symptoms within 10 years from diagnosis, whereas 18% had continuous activity.5 In general, CD has a more progressive and disabling clinical course, and a similar cohort study reported that only 10% of CD patients had prolonged clinical remission, and the annual incidence of hospitalizations was 20%6 Furthermore, the same study revealed that 50% of patients required surgery within 10 years from reaching the diagnosis, and one-third of patients was dependent on continuous glucocorticoid treatment in order to control the disease.6

The aetiology of IBD is unknown, but appears to be multifactorial in nature. Familial aggregation is evident, and genetically susceptible loci causing a dysregulated mucosal immune response has been identified in patients with IBD.7, 8 Environmental factors have also been strongly suspected to play a role, due to the higher disease incidences in developed countries compared to third-world countries and in urban vs. rural areas.9 Increasing incidence of IBD in Hispanics and Asians according to increasing standards of living (particularly among migrated Asians) is also an indicator that environmental factors play an important role.10 Gastrointestinal infections with certain agents such as Mycobacterium paratuberculosis, Listeria monocytogenes and paramyxocviruses are believed to increase the risk of both UC and CD, which has been interpreted as a mechanism where acute intestinal infection triggers a chronic inflammatory process in genetically predisposed individuals.11, 12

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IBD has a bimodal pattern of incidence reaching a maximum rate at 15-30 years of age and again at 50-70 years of age. Both UC and CD are evenly distributed among men and women.9, 13 Northern Europe and North America are high-incidence areas of IBD with UC being more prevalent than CD. In a cohort comprising the population of greater Copenhagen in the period 2003-2005, the annual incidence of UC was 13.4 per 100.000 persons and 8.6 per 100.000 persons for CD, which was a marked increase compared to previous studies within the same region between 1962-1987, which showed incidences per 100.000 persons of 8.1 for UC and 4.1 for CD, respectively.13-15 It is estimated that the prevalence of individuals with IBD is 30,000 in Denmark and 2.2 million in Europe, of whom roughly two-thirds have UC and the remaining one-third has CD.9, 13 Further, both incidence and prevalence are increasing worldwide, including in previously low-incidence areas.9, 16 Extraintestinal manifestations of IBD The pathology of IBD is not restricted to the gastrointestinal tract, and (notwithstanding the association with cardiovascular disease examined in the present thesis) extraintestinal manifestations include anaemia and musculoskeletal, dermatologic, hepatic and ocular complications.17, 18 Extraintestinal manifestations can be a result of the pathological processes seen in the intestinal tract in IBD, and are often thought to be caused by the same underlying immunologic disturbances as IBD.18 Therefore, extraintestinal manifestations often present prior to or parallel with onset of IBD, and diminish along with gastrointestinal symptoms in response to efficient IBD treatment.17, 18

Around 25-40% of patients with IBD are affected by extraintestinal manifestations. Chronic anaemia is very common in IBD, although most often caused by an inflammation-related malfunctioning iron metabolism rather than intestinal blood loss.19 Reports have suggested that up to three-quarters of IBD patients have asymptomatic sacroiliitis, and 10-35% suffer clinical manifestations from inflammatory arthropathies, with prevalences being highest among patients with CD.20 Musculoskeletal symptoms are also seen as reactive arthritis, secondary to intestinal infections.21 Erythema nodosum and pyoderma gangrenosum are dermatologic manifestations of IBD, with a prevalence of around 5% and 2%, respectively.17 Ophthalmologic complications including episcleritis, iridocyclitis, and uveitis are less common, and are mainly associated with coexisting joint and skin manifestations of IBD.17 In addition, hepatic manifestations of IBD may include primary sclerosing cholangitis.22 13

Inflammation in IBD The immune-inflammatory activation in IBD involves an array of mechanisms including the release of cytokines, e.g. tumor necrosis factor-α (TNF), interleukin-1, and platelet activating factor.1, 2 The balance between regulator and effector T helper cells (Th) is affected in IBD, with an atypical Th response.2323 Th1 and Th17 cells who normally act to defend the mucosa against microbes (e.g. bacteria, fungi and viruses) through secretion of interferon γ, TNF, and interleukins-17 and -22, are chronically up-regulated in CD, at the expense of downregulation of regulatory T cells secreting interleukin-10 and transforming growth factor.22 In UC, interleukin-13 has been suggested to play a key role in exerting cytotoxic effects involved in the abnormal Th response and thereby contributing to inflammation.24 24 The inflammatory activation may also trigger the coagulation cascade and thereby disrupt the hemostatic balance and induce thrombosis.25, 26 Indeed, it was recently demonstrated that only 12% of a small randomly selected group of IBD patients have haemocoagulation parameters within the normal range.27

Inflammation in cardiovascular disease The cardiovascular endpoints assessed in this thesis included myocardial infarction (MI), stroke, atrial fibrillation (AF), heart failure and cardiovascular death. These outcomes were chosen to reflect the most important and debilitating cardiovascular diseases, which demand early intervention and life-long treatment.

MI remains among the most common causes of death in worldwide, and AF is an important risk factor for ischaemic stroke, morbidity and mortality.28-32 In up to 30% of patients, no apparent reason for AF is identified.33 Heart failure is also a major cause of mortality and morbidity in the western world and is usually accompanied by a number of symptoms of decreased cardiac output including oedema, dyspnoea and fatigue. A common denominator for these diseases is that early cardioprotective pharmacotherapy is crucial for ameliorating the prognosis and survival.34 Atherosclerosis, which is the underlying condition that primarily causes arterial thrombotic events, is triggered by mobilization and activation of immune cells, including macrophages and leukocytes that migrate into the arterial wall and elicit an inflammatory response.35-37 Accordingly, atherothrombotic events have been associated with increased sedimentation rate and circulating levels of inflammatory biomarkers and agents such as C-reactive protein (CRP), interleukin-6,

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intercellular adhesion molecule-1, and leukocytes.37, 38 Also, inflammatory activation has been shown to contribute to the development and progression of heart failure.39-42 Heart failure frequently progresses from asymptomatic to severe disease and as this evolution can be countered by appropriate therapies, early diagnosis and prevention is crucial.43 Several studies have indicated that inflammatory activation holds an important role in the aetiology and perpetuation of AF.44-47 Mechanisms linking inflammation and AF are, however, poorly understood, but may include atrial myocarditis with infiltration of inflammatory cells in the atrial wall.47

Common features in the pathogenesis of IBD and cardiovascular disease The pathophysiological mechanisms in the intestinal tract of patients with IBD share several features with the processes seen during progression of atherosclerosis and, ultimately, plaque rupture and thrombosis.48-50 Rheumatoid arthritis, psoriasis, coeliac disease and systemic lupus erythematosus have also all been associated with an increased risk of cardiovascular disease.51-55 Further, a disease severity-dependent increased risk of MI and stroke has been described in patients with rheumatoid arthritis and psoriasis.56, 57 The chronic inflammatory state in IBD may also contribute to the development of heart failure by translocation of bacterial lipopolysaccharides from the bowel to the circulation. This can potentially stimulate production of proinflammatory mediators and tissue injury that can contribute to myocardial damage.39, 40 In aggregate, these findings suggest that the systemic inflammatory burden in IBD may be an important determinant of cardiovascular risk, mediating its effect both directly, but also indirectly by promoting insulin resistance, dyslipidaemia, and endothelial dysfunction.58

Prior research has mainly focused on the association between IBD and the risk of venous thromboembolic disease (VTE), and not on arterial cardiovascular disease. These studies have revealed an increased risk of VTE in patients with IBD, and one study demonstrated a more than 8fold increase in risk of VTE during active IBD, as defined by dispensed glucocorticoid prescriptions.26, 59-62As a result, IBD is considered to be an established risk factor for VTE, which has led to recommendations of standardized antithrombotic prophylactic treatment during hospitalizations due to flares of IBD.63, 64 However, the risk of atherotrombotic disease, AF and heart failure in patients with IBD has remained unclear with conflicting results regarding the former two, and almost no data available on AF and heart failure risk.48, 65-70

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With respect to traditional cardiovascular risk factors such as hypertension, dyslipidaemia and obesity, it is notable that these also appear to exhibit increased prevalence in patients with, chronic inflammatory disease, and adjustment for such factors is therefore important in studies to ascertain the independent contribution of inflammation to the risk of cardiovascular disease.71-74 IBD pharmacotherapy in relation to cardiovascular disease Apart from the desired effects on IBD symptoms, the pharmacotherapy used in the treatment of IBD (particularly during flares and persistent activity) has a number of adverse effects, some of which must be taken into consideration when evaluating the risk of cardiovascular disease. Specifically, the role of glucocorticoids in cardiovascular disease remains controversial.75 For example, glucocorticoids are suspected to increase blood pressure, cause dyslipidaemia, have prothrombotic effects, and diminish myocardial recovery from ischaemic injury.56 Nevertheless, it remains questionable whether these agents add to the risk of atherothrombotic disease and heart failure in patients with IBD, as glucocorticoids might also have potential benefits due to their antiinflammatory effects.75, 76 Indeed, in a cohort of rheumatoid arthritis patients, glucocorticoids were not associated with an increased risk of heart failure, which indicated that beneficial antiinflammatory effects might counterbalance any adverse cardiovascular effects.77

Anti-TNF agents are potent anti-inflammatory drugs and are being used increasingly in the treatment of IBD.78, 79 Therefore, it is of particular interest that anti-TNF agents might reduce cardiovascular risk, as indicated by studies of patients with rheumatoid arthritis.80, 81 No study has specifically examined the cardiovascular safety of TNF inhibitors in IBD, but a very recent study found no association between these agents and risk of heart failure was in a cohort of rheumatoid arthritis patients.82 In patients with mild chronic heart failure, TNF inhibitors have even been tested in clinical trials for cardioprotective effects but failed to show any clinical efficacy, which could be due to the redundancy of the inflammatory pathways and the multifactorial nature of heart failure pathogenesis.83-85 Interestingly, two ongoing clinical trials are testing a potential role of antiinflammatory treatment (methotrexate and interleukin-1β inhibition, respectively) for secondary prevention in patients with known ischaemic heart disease.86, 87 Results from these trials will greatly help to clarify whether antiinflammatory drugs have significant beneficial cardiovascular effects.

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Objectives Utilising a large nationwide database, we sought to clarify whether IBD was associated with an increased risk of cardiovascular outcomes including MI, stroke, AF and heart failure. Conflicting results, and growing evidence of cardiovascular risk in other chronic inflammatory diseases, combined with the increased focus on the role of inflammation in the development and progression of cardiovascular disease inspired the body of work leading to this thesis. In addition, the high and rising prevalence of IBD makes any link to an increased risk of cardiovascular disease of public health relevance. Consequently, we aimed to examine the following hypotheses:

1.

IBD is associated with an increased risk of MI, stroke, AF, and heart failure.

2.

The risk of adverse cardiovascular events in IBD patients is correlated to periods

3.

of active disease.

3.

IBD is associated with worsened prognosis after a first-time MI.

Methods Databases The basis of this thesis was the comprehensive nationwide Danish healthcare- and civil registry databases. Since 1968, the Danish Civil Registration System has assigned unique and permanent identification numbers to all individuals with permanent residence in Denmark. Information in the register includes name, gender, date and place of birth, citizenship and is continuously updated for information on vital status, place of residence, taxed income and migration status for each individual.88 The personal identification number is used in all interactions with government agencies and includes all contacts with the tax-funded public health care system in Denmark.89 Contacts with the health care system are registered in The National Patient Registry which holds information on hospitalizations since 1978, outpatient activities since 1995, and invasive procedures since 1996.90 Each contact is coded by up to four diagnoses, with the main reason for hospitalization as the primary diagnosis, listed according to the International Classification of Diseases (ICD) system, 8th revision (ICD-8) until 1994, and the 10th revision (ICD-10) subsequently. Invasive procedures are listed using the Nordic Medical Statistics Committees Classification of Surgical Procedures.

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The Danish Register of Medicinal Product Statistics holds information on drug quantity dispensed, dose and dispensing date for all prescriptions, registered according to the Anatomical Therapeutical Chemical (ATC) classification since 1995.91 Partial reimbursement of drug expenses by the healthcare system yields a comprehensive registry with quality data. All deaths, including immediate, contributory and underlying causes, are registered by ICD codes in the National Causes of Death Registry.92 By accessing encrypted versions of the unique personal identification numbers, we were able to perform individual level-linkage of data across these nationwide registries. All data were accessed and analyzed through secure servers placed at Statistics Denmark (Office for National Statistics). Statistics Denmark arranged the coupling of registries, and encrypted the identification numbers to ensure anonymity.

Study design The study design varied according to the research question investigated, despite all studies being registry-based data analyses. Inclusion- and exclusion criteria varied for each study according to the individual study aims, as depicted in Table 1. Exclusion criteria were applied to both cases and controls. The participants in the four studies comprising this thesis were identified from the general Danish population as listed in the Danish Civil Registration System. Identification of subjects with IBD Subjects with new-onset IBD were identified from the general population by using a combination of hospital diagnoses and drug prescriptions (supplementary Tables 1 & 2). Thus, they were required to have a first-time diagnosis of IBD (CD or UC), as well as a prescription of pharmacological IBD treatment dispensed within a period of one year before or after the diagnosis. Pharmacological IBD treatment was defined as the following agents: Mesalazine, sulfasalazine, oral glucocorticoids including budesonide, azathioprine, 6-mercaptopurine, methotrexate and/or biological treatment with TNF inhibitors. Date of IBD onset was set as the last of either date of diagnosis or date of dispensed prescription of IBD pharmacotherapy, to avoid inclusion of risk time conditioned on future events in the analyses. Patients who received any IBD pharmacotherapy (excluding glucocorticoids) more than one year prior to the date of first IBD diagnosis were excluded. In Paper IV, the criterion for IBD was less stringent as IBD at time of MI was defined solely by a prior diagnosis of IBD.

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Cohorts Papers I+II Risk of MI, stroke and AF The study population comprised subjects with new onset IBD and matched controls. All eligible subjects, aged 15 years or more, who met the IBD criteria in between 1 January 1996 and 31 December 2009 (Paper I), or in between 1 January 1996 and 31 December 2011 (Paper II) were identified. At time of IBD onset, each subject was randomly matched by age and sex with up to ten controls from the general population using the Greedy matching macro http://mayoresearch.mayo.edu/mayo/research/biostat/upload/gmatch.sas. The main advantage of this matching approach was that it allowed for direct comparison of IBD patients and controls in terms of comorbidity, cardiovascular pharmacotherapy, as well as it resulted in similar follow-up time.

Paper III Risk of heart failure For this study, we used a different approach, as the entire Danish population was included in the study and used as the reference group. All Danish inhabitants aged 18 years and more in between 1 January 1997 and 31 December 2011, were included. As a consequence, subjects who developed IBD within the studied timeframe were included in the reference population and changed status from non-case to case at date of IBD onset. This approach meant that covariates and unadjusted event rates were not directly comparable, as both age and sex distribution varied considerably between IBD patients and the reference population. A major advantage of this design was the ability to investigate absolute event rates, which are less meaningful in highly selected control groups.

Paper IV Post MI prognosis The population in this study consisted of all Danish inhabitants aged 30 years and older, who suffered a first-time MI in the period 1 January 2002 until 31 December 2011. This study cohort differed from the other studies, by following the cohort from time of first MI as compared to time of IBD onset, and being consequently smaller in size. IBD was identified solely by a prior discharge diagnosis, which was a less stringent criterion, as compared to Study I-III. The rationale behind this decision was the lesser importance of the exact onset of IBD in this study.

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IBD disease activity In order to determine the influence of IBD activity stages on cardiovascular risk in patients with IBD, we used surrogate markers including i) hospitalizations with IBD as primary diagnosis, ii) initiation of anti-TNF treatment, and iii) dispensed prescription of glucocorticoids. By use of a combination of these markers, we defined the disease activity state of each IBD patient over time as being in remission, flare or persistent activity (Figure 1). Patients were defined as being in remission starting 120 days after last disease activity (IBD hospitalization, anti-TNF treatment or glucocorticoid prescription), and remission continued in the absence of further disease activity. Disease activity following a remission period was used to define a flare which was set to 120 days duration. Likewise, the first 120 days following IBD onset was defined as a flare. Finally, we defined periods of persistent activity, which succeeded flares if additional disease activity occurred within the 120 days from flare start, and continued until a 120 day period without further activity had passed. Figure 1 Example of disease activity in a patient with inflammatory bowel disease (IBD)

Outcome predictors In all four papers, risk estimates were adjusted for age, sex, annual income at baseline and calendaryear. Further, we adjusted for predefined comorbidities and cardiovascular pharmacotherapy, chosen according to the evaluated endpoints, and hence they differed slightly between the studies (Table 1). Comorbidity and pharmacotherapy were included in the regression models as timevarying covariates in Paper I-III. In Paper IV, covariates were fixed at baseline (7 days after discharge for first MI), and selected according to the Ontario Acute MI Mortality Prediction 20

Rules.93, 94 The rationale behind the altered approach was that all subjects in Paper IV had suffered an MI, and that the study period and follow-up period were markedly shorter than the other studies.

Ethics The research protocol was approved by the Faculty of Health Sciences, University of Copenhagen, Denmark, and register-based studies do not require ethical approval in Denmark.

Individual

patients were not identifiable as the personal identification numbers were encrypted. The Danish Data protection agency approved the study (reference no. 2007-58-0015,/ I.suite no. 00916 GEH2010-001).

Statistical analyses Baseline characteristics were presented as means with standard deviations for continuous variables and as frequencies and percentages for categorical variables. Incidence rates (IRs) of the different endpoints were presented for subjects with and without IBD. Estimates of IBD-associated risks were fitted with Poisson regression models and presented as incidence rate ratios (IRRs) in Papers I-III. In the post MI study (Paper IV), we used two different models: A logistic regression model to estimate odds ratios (ORs) for the event of death during hospitalization or within seven days of discharge and for patients alive seven days after discharge, we used a Cox regression model to estimate hazard ratios (HRs) for IBD-associated risks during follow-up.

The choice of Poisson regression models in the first three papers was based on the large datasets present with numerous observations, time varying covariates, and multiple timescales.95 In Poisson regression models time bands were split in 1-year intervals from 1 January 1997, with updated age for each time band. In IBD activity analyses we categorized exposure-time as flare, persistent activity, or remission. The assumption of a constant rate of examined variables within each timeband was tested and confirmed by demonstrating the same results with a finer split of 6 months.

Cox regression was used in Paper IV because the study population here was smaller, with fewer observations and a primary timescale, i.e. time from first MI. In practice, however, the two regression models provide comparable results.96 Logistic regression is normally applied in crosssectional studies, and we used it for the short-term binary outcome of mortality according to IBD activity, in a model solely adjusted for age and sex.97, 98

21

For Poisson and Cox regression estimates, analyses adjusted for age, and sex, as well as analyses controlling for comorbidity and pharmacotherapy were presented in order to illustrate the effects of measured confounders. In both types of regression models, we tested the assumption of linearity of continuous variables by demonstrating that quartiles of these variables did not improve model fit, and further, clinical relevant interactions between covariates were tested for, and if present, prompted stratified analyses.

SAS version 9.2 and Stata version 11.1 were used for all statistical analyses. The studies were conducted and reported in accordance with the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines.21 In Study I, evaluation of the significance of an unmeasured confounder was made using the “rule out” approach for all reported results.99

22

Table 1 Summary of methods used in the individual studies. For abbreviations, see text.

Paper I

Paper II

Paper III

Study objective

To investigate the incidence of MI, stroke and CV death in IBD, compared to the general population.

To investigate the incidence of AF, and stroke in IBD compared to the general population.

To evaluate the incidence of heart failure in IBD compared to the general population.

To determine the prognostic impact of co-existent IBD when suffering a first-time MI.

Design

Register-based cohort study of a nationwide population of IBD patients and a matched control group.

Register-based cohort study of a nationwide population of IBD patients and a matched control group.

Register-based cohort study of the entire Danish population aged ≥18 years.

Register based cohort study of a nationwide population of first-time MI patients.

Cohort and study entry

Danish inhabitants fulfilling the criteria for new-onset IBD in between 1996 and 2009 and 10 matched population controls entered the study on the date of IBD onset

Danish inhabitants fulfilling the criteria for new-onset IBD in between 1996 and 2011, and 10 matched population controls entered the study on the date of IBD onset.

All Danish inhabitants aged ≥18 years in between 1997 and 2011. The IBD exposure was timedependent, thus subjects contributed risk-time to the control group until IBD onset.

All Danish inhabitants aged ≥30 years who suffered a first-time MI in between 2002 and 2011.

Exclusion criteria

Subjects with prior IBD, MI or stroke were excluded.

Subjects with prior IBD, MI or AF were excluded.

Subjects with prior IBD, MI or AF were excluded.

No patients were excluded.

Follow-up

Until MI, stroke, death, migration or 31 December 2009.

Until AF, stroke, death, migration or 31 December 2011.

Until heart failure, death, migration or 31 December 2011.

Until recurrent MI, death, migration or 31 December 2011.

Exposures

IBD and disease activity: Flares, persistent activity and remission.

IBD and disease activity: Flares, persistent activity and remission.

IBD and disease activity: Flares, persistent activity and remission.

IBD prior to MI and disease activity: Flares, persistent activity and remission.

23

Paper IV

Paper I

Paper II

Paper III

Paper IV

Outcomes

MI, stroke, CV death, and a composite endpoint of MI, stroke, CV death, defined as hospitalization with ICD-10 codes I21-I22 (MI), I60-I61, I63-I64 (stroke).

AF and stroke defined as hospitalization with ICD-10 codes I48 (AF), I60-I61, I63-I64 (stroke).

Heart failure defined as hospitalization with ICD-10 codes: I50, J81.9

MI, all-cause mortality, composite of CV death, recurrent MI, stroke defined as hospitalization with ICD10 codes I21-I22 (MI), I60-I61, I63I64 (stroke).

Outcome predictors

Sex, age, income, calendar-year. Comorbidity: AF, diabetes, COPD, renal disease, hypertension, VTE and heart failure. Pharmacotherapy: glucose-lowering agents, VKA, statins loop diuretics, platelet inhibitors, anti-hypertensive treatment.

Sex, age, income, calendar-year. Comorbidity: Diabetes, IHD, COPD, renal disease, hyper-tension, VTE, valvular heart disease, heart failure, hyperthyroidism. Pharmacotherapy: glucose-lowering agents, loop diuretics, statins, anti-thyroid agents, anti-hypertensive treatment.

Sex, age, income, calendar-year. Comorbidity: AF, VTE, diabetes, COPD, renal disease, hypertension, and vascular disease. Pharmacotherapy: glucose-lowering agents, statins, antiplatelets, antihypertensive treatment.

Sex, age, income, calendar-year, Comorbidity: according to Ontario MI prediction rule Pharmacotherapy: Platelet inhibitors, glucose-lowering agents, beta blockers, loop diuretics, VKA, statins, spironolactone.

Statistical analyses

Multivariable Poisson regression model, fitted to estimate the IRR, comparing IBD patients, and disease activity stages with the matched controls.

Multivariable Poisson regression model, fitted to estimate the IRR, comparing IBD patients, and disease activity stages with the matched controls.

Multivariable Poisson regression models fitted to estimate the IRR, comparing IBD patients and disease activity stages with the general Danish population.

Logistic regression, estimating odds ratios for death during hospitalization or within seven days of discharge. Multivariable Cox regression models were fitted to estimate the HR, comparing the IBD-group, with the remaining MI population, In patients alive seven days after discharge.

24

Results This section presents the main findings of the four studies constituting the thesis.

Figure 2 Flowchart of the study population in Paper I

Paper I: Increased risk of MI, stroke and cardiovascular death From 1996-2009 we identified 20,795 IBD patients with a mean age of 40.3 years (SD 18.7) that were matched, according to age and sex with 199,978 controls (Figure 2). Among patients with IBD, 365 had a MI, 454 a stroke and cardiovascular death occurred in 778 patients. Patients with IBD had increased risk of MI (IRR 1.17 [95% confidence interval [CI] 1.05-1.31]), stroke (IRR 1.15 [1.04-1.27], and cardiovascular death (IRR 1.35 [1.25-1.45]) (Figure 3). During active disease, i.e. flares and persistent activity the risk of MI increased to IRR 1.49 (1.16-1.93) and 2.05 (1.582.65), and for stroke to IRR 1.53 (1.22-1.92) and 1.55 (1.18-2.04), respectively. The risk of cardiovascular death was more than doubled during flare and persistent activity: IRR 2.32 (2.01-2.68) and 2.50 (2.14-2.92), whereas in periods of remission, the risk of MI, stroke and cardiovascular death was similar to controls. 25

In conclusion, IBD was associated with increased risk of MI, stroke, and cardiovascular death during periods with active disease. Figure 3 Risk of myocardial infarction, stroke and cardiovascular death in Paper I

26

Paper II: Increased risk of AF and stroke Figure 4 Flowchart of the study population in Paper II

A total of 24,499 patients with new-onset IBD and 236,275 age- and sex-matched controls (Figure 4) were identified from Danish nationwide registries 1996-2011. Poisson regression analyses with continuously updated covariates were used to estimate IRRs of AF and stroke. Disease activity stages of flare (new disease activity), persistent activity, and remission were defined by glucocorticoid prescriptions, IBD hospital admissions, and biological treatment. IBD patients had a mean age of 43.9 (SD 19.1), years 53.9 % were women, and mean follow-up time was 6.8 years. Among IBD patients, 685 had AF and 549 had stroke, corresponding to incidence rates per 1,000 person-years of 4.16 vs. 2.70 for AF and 3.33 vs. 2.44 for stroke, compared to matched controls. Overall IBD-associated risk of AF corresponded to IRR 1.26 (1.16-1.36), but was driven by increased AF incidence during IBD flares (IRR 2.63 [2.26-3.06]) and persistent activity (IRR 2.06 [1.67-2.55]), whereas no increased AF risk was observed in remission periods (IRR 0.97 [0.881.08]). Similar to AF risk, the risk of stroke was found to be increased during active stages of IBD with IRR 1.57 (1.27-1.93) during flares and IRR 1.71 (1.32-2.21) in periods of persistent activity, and no increased risk during remission (Figure 5). In conclusion, active IBD was associated with a more than doubled risk of AF whereas increase in stroke risk was less pronounced, as compared to the matched population. 27

Figure 5 Incidence rates and risk of atrial fibrillation and stroke

28

Paper III: Risk of hospitalization for heart failure in patients with IBD Figure 6 Flowchart of the study population in Paper III

During a mean follow-up of 11.8 years in the reference population and 6.4 years in the IBD group, hospitalization for heart failure occurred in 553 subjects with IBD, and 171,405 in the reference population. This corresponded to crude incidence rates of 3.68 and 2.69 per 1000 person-years, respectively. Patients with IBD had a 37% increased risk of hospitalization for heart failure (IRR 1.37 [1.26-1.49]) compared to the reference population. IBD activity-specific analyses showed markedly increased risk of hospitalization for heart failure during flares (IRR 2.54 [2.13-3.04]) and persistent activity (IRR 2.73 [2.25-3.33]) but no increased risk in quiescent stages (IRR 1.04 [0.941.16]). In conclusion, the risk of hospitalization for heart failure was a more than doubled during active stages of IBD. Figure 7 Risk of hospitalization for heart failure in patients with inflammatory bowel disease (IBD) compared to the reference population

29

Paper IV: Prognosis after first-time MI Figure 8 Flowchart for study population in Paper IV

We identified 86,790 first-time MI patients 2002-2011 in the nationwide registries. Activity of IBD was categorized in stages of flare, persistent activity or remission. Short-term mortality was estimated in a logistic regression model, whereas risks of recurrent MI, all-cause mortality, and a composite of recurrent MI, cardiovascular death, and stroke were estimated by Cox regressionmodels. Death during hospitalization or within seven days of discharge occurred in 11,502 patients (including 138 with IBD). For patients with IBD, this corresponded to odds ratios of 1.74 (95% [confidence interval] CI 1.09-2.77) for patients in IBD flares, 1.25 (0.71-2.20) for persistent activity, and 0.92 (0.74-1.14) for remission. Among the 75,288 patients, including 892 with IBD, alive seven days after discharge, 9,730 had recurrent MI, 23,167 died, and the composite endpoint occurred in 21,722 patients during a mean follow-up of 3.9 years. As compared to the remaining patients IBD was associated with HRs of 1.12 (0.95-1.38) for MI, 1.16 (1.03-1.30) for death, and 1.10 (0.97-1.24) for the composite endpoint, respectively. IBD flares following discharge for MI were associated with increased risks of recurrent MI (HR 2.70 [95% CI 1.63-4.48]), all-cause mortality (HR 2.47 [95% CI 1.83-3.35]) and the composite endpoint (HR 1.80 [95% CI 1.21-2.66]), whereas no increased risk was identified in remission.

30

In conclusion, patients with IBD had increased risk of all-cause mortality and major adverse cardiovascular events after MI, and this risk was exclusively observed during active IBD, in particular in relation to flares. Figure 9 Risk of major adverse cardiovascular events after first-time myocardial infarction

31

Discussion In this thesis we investigated the IBD-associated cardiovascular risk in a nationwide population using a register-based approach. In the period from 1996 until 2011, we identified around 25,000 patients with new onset IBD, and compared their cardiovascular risk with population controls matched on age and gender (Paper I-II), or the entire Danish population (Paper III). The basis of Paper IV was a first-time MI population stratified by prior IBD. Our studies showed that patients with IBD were at increased risk of MI, stroke, AF and heart failure, and there was a strong correlation between periods of active IBD and cardiovascular risk. Patients with IBD had a higher risk of death following MI compared to controls, and in these subjects active IBD at the time of MI (and during subsequent follow-up) was also associated with the burden of increased cardiovascular risk.

Comparison to findings in other studies MI, stroke and cardiovascular death In patients with IBD we found an increased risk of MI, stroke, and cardiovascular death in periods of active disease, whereas no increased risks were observed in periods of IBD remission. The association between IBD disease activity and risk of MI, stroke and CV death indicated that inflammatory activation contributed to the pathophysiological mechanisms of these atherothrombotic manifestations, and is in accordance with recent findings of an augmented VTE risk in IBD.59, 60 Patients with CD had a tendency towards a higher risk of stroke and cardiovascular death compared to those with UC, but we found a parallel increased risk regardless of IBD entity during periods of flares and persistent activity.

The increased risk of VTE in subjects with IBD is well-established, whereas results on atherothrombotic disease such as MI and stroke have been conflicting and have fostered much debate.48, 59, 60, 65, 68, 70, 100 A 2007 meta-analysis of 11 studies found no increased risk of cardiovascular mortality.66 Two registry-based studies, similarly reported that the risk of MI in IBD patients was comparable to matched controls.65, 68 Contrary to these results, two more recent metaanalyses concluded that IBD was associated with a moderately increased risk of arterial cardiovascular events.69, 101 A Canadian study of 8,000 IBD patients reported an increased risk of 32

ischaemic heart disease whereas increased risk of stroke was only significant among patients with CD.50 In a cohort of patients with CD from the UK General Practice Research Database, an increased risk of stroke in patients 1 year prior to diagnosis, to make sure we only included patients with new-onset disease, and to exclude patients with very mild disease treated by their general practitioner only. We defined IBD pharmacotherapy as the following drugs: 5aminosalicylic acid, sulfasalazine, oral glucocorticoids including budesonide, azathioprine, 6mercaptopurine and methotrexate. In studies I-III where nationwide populations of patients with IBD were used, we found slightly different number of incidence, according to varying study length and exclusion criteria. However, the number of patients identified by IBD treatment agents in combination with a diagnosis corresponded closely to the numbers observed in previous Danish studies.13

IBD disease activity was estimated indirectly by use of predefined surrogate markers, i.e. glucocorticoid prescriptions, biological treatment and primary IBD admissions. Information on the anatomical extent of the disease, as well as on inflammatory biomarkers (e.g. leukocyte and CRP levels) was not available and could potentially have contributed to a more exact definition of IBD activity. The criteria used to stratify IBD disease was inspired by a British study on IBD and VTE which used corticosteroid prescriptions to estimate disease activity.60 In the present studies we extended this definition by including initiation of biological treatment and primary IBD hospitalizations. We would have preferred to use individual data on flare duration but this was not possible due to the registry-based approach, and therefore we defined that a flare lasted for 120 days. In a cohort of IBD patients, a new prescription for glucocorticoids had a positive predictive value of 85% for identification of an IBD flare, whereas the positive predictive value for remission in patients 120 days after last prescription was 91%.117 A 120 days period was therefore considered to be in agreement with experience from clinical practice.60 In addition, sensitivity analyses with 38

flare durations of 60 and 180 days, respectively, were performed in study I-III, and here comparable results were found. Finally, since we used IBD treatment to establish disease activity it is possible that pharmacological IBD treatment, e.g. glucocorticoids could be independently associated with an increased risk of adverse cardiovascular events. However, a sensitivity analysis where we excluded patients with COPD (who are frequently treated with glucocorticoids) did not considerably alter the results.75 Also, in sensitivity analyses performed in study I, when we excluded the use of corticosteroids as an IBD activity marker, the strong association between disease activity and cardiovascular risk persisted.

Outcomes The diagnostic coding of MI and stroke in the National Patient Registry has been validated with high sensitivity and specificity.118, 119 For AF, and heart failure, specificity is also high, whereas particularly for heart failure the sensitivity is low.120, 121 This issue was addressed in study IV by sensitivity analyses with use of a composite of either diagnosis of heart failure or prescribed loop diuretics as a surrogate marker of heart failure. In study IV, the study population consisted of firsttime MI patients, and we assessed the endpoint of recurrent MI. We defined recurrent MI as rehospitalization with MI as the primary diagnosis to avoid repeated coding of the first MI in connection with subsequent hospitalizations for other causes. This method has previously been validated with a positive predictive value of more than 90%.122 The use of cardiovascular death as determined from death certificates and registered in the National Causes of Death Register has not been validated, due to the low number of autopsies performed in Denmark, but data from other countries suggest that the number of cardiovascular deaths is often overestimated.123

39

Conclusions In a nationwide cohort of around twenty-five thousand patients with IBD, using information on glucocorticoid prescriptions, biological treatment and IBD hospitalizations, we identified strong associations between IBD disease activity and risk of cardiovascular outcomes including MI, stroke, AF and heart failure, whereas the risk was comparable to the background population when IBD was quiescent. Overall, IBD was associated with moderately increased risk of the examined cardiovascular endpoints and mortality. Furthermore, at time of a first MI (or during subsequent follow-up) active IBD increased the risk of recurrent MI and death from all causes. Our findings of a strong IBD activity-dependent cardiovascular risk parallel findings in other acute and chronic inflammatory conditions including rheumatoid arthritis and psoriasis. The results emphasize that chronic inflammation and acute exacerbations hereof increase the risk of cardiovascular disease.

Clinical implications and future research This thesis presents new evidence of an association between IBD and increased risk of cardiovascular disease, and highlights that this excess risk is present predominantly, if not exclusively, during periods of active disease. Thus, our results indicate that aggressive treatment aimed at minimizing length and number of disease activity episodes in patients with IBD could potentially lower their cardiovascular risk. Moreover, our findings reinforce the need for thorough cardiovascular evaluation and surveillance of patients with IBD, in particular in relation to flares. Whether the growing and widespread use of TNF inhibitors at the expense of glucocorticoids and other traditional drugs in the treatment of IBD can attenuate the cardiovascular risks associated with the disease, is an interesting and important future question. A Danish registry of the use of TNF inhibitors for IBD is under development and will facilitate studies to answer such questions. This registry might also pave the way for clinical interventional studies, aimed at reducing cardiovascular risk in patients with IBD, e.g. by first-line treatment of IBD flares with TNF inhibitors, and thromboprophylaxis for IBD patients during flares and hospitalizations. Also, the results of ongoing trials of anti-inflammatory treatment in high risk patients with ischaemic heart disease in absence of other inflammatory conditions should allow for insights to determine whether reduction of inflammation can reduce cardiovascular disease. 40

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Appendices Supplementary tables Supplementary table 1 Diagnoses and treatment procedure codes used for defining the study population, comorbidities, and outcomes Exposures

ICD-10 / ICD-8 codes:

Myocardial infarction

I21, I22 / 410

Inflammatory bowel disease: Ulcerative colitis

K51 / 569.05, 563.19

Crohn´s disease Comorbidity

K50 / 563.01

Hypertension

I10-I15 /400-404 E10-E14 / 250

Diabetes mellitus Valvular heart disease

I33-I36 / 105-107

Renal disease

N03, N04, N17-19, R34, I12, I13 / 582-588

Chronic obstructive pulmonary disease

J42-J44 / 491,492 I80, I82 (excluding 80.0, I80.8and I82.0 /415, 453

Venous thrombo-embolic disease Outcomes: Myocardial infarction

I21, I22 / 410

Stroke

I60-I61, I63-I64 / 430-434, 436

Atrial fibrillation

I48 / 427.93 427.94

Heart failure

I42, I43, I50 / 110. 517

Cardiovascular death

I00-I99 as cause of death.

Procedures:

NCSP codes:

PCI

KFNG

CABG

KFNA, KFNB, KFNC, KFNE

Treatment with anti-TNF agents

BHJ18A

ICD-8:

8th revision of the International Classification of Diseases system

ICD-10:

10th revision of the International Classification of Diseases system

NCSP:

The Nordic Medical Statistics Committees Classification of Surgical Procedures

PCI:

Percutaneous coronary intervention

CABG:

Coronary artery bypass grafting

NCSP:

Nordic Medico-Statistical Committee Classification of Surgical Procedures

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Supplementary Table 2 Pharmacological treatment and Anatomical Therapeutical Chemical (ATC) codes Pharmacotherapy

ATC codes:

Aspirin

BO1AC06, NO2BA01 BO1AC04

Clopidogrel Beta blockers Cholesterol-lowering agents ACE inhibitors/ARBs Loop diuretics Thiazides Calcium-channel blockers Vitamin K antagonists

C07 C10A C09 C03C C03A C08 BO11AA0

Spironolactone

I12, I13, N18, T82.4, Z99.2

Glucose-lowering agents Azathioprine

I47-I49, I46.0, I46.9, R00.1 L04AX01

Methotrexate

L01BA01 / L04AX03

Sulfasalazine

A07EC01

5-ASA

A07EC02

6-mercaptopurine

L01BB02

Rectal glucocorticoids

A07EA

Oral glucocorticoids

H02AB

Hypertension (a-antagonists, non-loop-diuretics,

Defined from combination treatment with a least

vasodilators, beta-blockers,

two classes of anti-hypertensive drugs

calcium-channel blockers, and renin–angiotensin system inhibitors.)

ACE inhibitors: Angiotensin-converting enzyme inhibitors ARBs: Angiotensin II receptor blockers

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Appendix I (Paper I) Disease activity in inflammatory bowel disease is associated with increased risk of myocardial infarction, stroke and cardiovascular death – a Danish nationwide cohort study. Kristensen SL, Ahlehoff O, Lindhardsen J, Erichsen R, Jensen GV, Torp-Pedersen C, Nielsen OH, Gislason GH, Hansen PR. PLoS One. 2013. 2013;8(2)

Appendix II (Paper II) Increased risk of atrial fibrillation and stroke during active stages of inflammatory bowel disease: a nationwide study. Kristensen SL, Lindhardsen J, Ahlehoff O Erichsen R, Lamberts M, Khalid U, Torp-Pedersen C, Nielsen OH, Gislason GH, Hansen PR. Europace. 2014;16,477-484

Appendix III (Paper III) Inflammatory bowel disease is associated with an increased risk of hospitalization for heart failure. Kristensen SL, Ahlehoff O, Lindhardsen J, Erichsen R, Lamberts M, Khalid U, Torp-Pedersen C, Nielsen OH, Gislason GH, Hansen PR. Submitted 2014.

Appendix IV (Paper IV) Prognosis after first-time myocardial infarction in patients with inflammatory bowel disease according to disease activity: A nationwide cohort study. Kristensen SL, Ahlehoff O, Lindhardsen J, Erichsen R, Lamberts M, Khalid U, Torp-Pedersen C, Nielsen OH, Gislason GH, Hansen PR. Submitted 2014

50

Paper I

51

Paper II

52

Paper III

Inflammatory bowel disease is associated with an increased risk of hospitalization for heart failure: A Danish nationwide cohort study Søren Lund Kristensen, MD*; Ole Ahlehoff MD, PhD*†; Jesper Lindhardsen, MD, PhD*; Rune Erichsen, MD, PhD**; Morten Lamberts, MD*; Usman Khalid, MD*; Ole Haagen Nielsen, MD, DMSc#; Christian Torp-Pedersen, MD, DMSc††*; Gunnar Hilmar Gislason, MD, PhD*‡; Peter Riis Hansen, MD, DMSc, PhD* *

Department of Cardiology, Copenhagen University Hospital Gentofte, Denmarks Department of Cardiology, Copenhagen University Hospital Roskilde, Denmark ** Department of Clinical Epidemiology, Aarhus University Hospital, Denmark # Department of Gastroenterology, Copenhagen University Hospital Herlev, Denmark †† Department of Health, Science and Technology, Aalborg University, Aalborg, Denmark ‡ National Institute of Public Health, University of Southern Denmark, Copenhagen, Denmark †

Background Inflammatory bowel disease (IBD) has been linked to adverse cardiovascular events, but a relation to heart failure is uncertain. We investigated the IBD-associated risk of heart failure in a nationwide setting. Methods and results A total of 5,436,647 Danish citizens, with no history of IBD or heart failure, were included on 1 January 1997 and followed until first hospitalization for heart failure, death, or 31 December 2011. Of these subjects, 23,681 developed IBD for which disease activity was determined continuously throughout the study. The risk of hospitalization for heart failure was estimated with a Poisson regression model adjusting for comorbidity and cardiovascular pharmacotherapy as time-dependent covariates. During a mean follow-up of 11.8 years in the reference population and 6.4 years in the IBD group, hospitalization for heart failure occurred in 553 subjects with IBD, and 171,405 in the reference population. Patients with IBD had a 37% increased risk of hospitalization for heart failure (incidence rate ratio [IRR] 1.37, 95% confidence interval [CI] 1.26-1.49) compared to the reference population. IBD activity-specific analyses showed markedly increased risk of heart failure hospitalization during flares (IRR 2.54, 95% CI 2.13-3.04) and persistent activity (IRR 2.73, 95% CI 2.25-3.33]) but not in IBD remission (IRR 1.04, 95% CI 0.94-1.16). Conclusion In a nationwide cohort, IBD was associated with an increased risk of hospitalization for heart failure, and this risk was strongly correlated to periods of active disease. The mechanisms underlying this finding warrant further studies.

53

Paper IV

Prognosis after first-time myocardial infarction in patients with inflammatory bowel disease according to disease activity: A nationwide cohort study Søren Lund Kristensen, MD*; Ole Ahlehoff MD, PhD*†; Jesper Lindhardsen, MD, PhD*; Rune Erichsen, MD, PhD**; Morten Lamberts, MD*; Usman Khalid, MD*; Ole Haagen Nielsen, MD, DMSc#; Christian Torp-Pedersen, MD, DMSc††*; Gunnar Hilmar Gislason, MD, PhD*‡; Peter Riis Hansen, MD, DMSc, PhD* *

Department of Cardiology, Copenhagen University Hospital Gentofte, Denmark Department of Cardiology, Copenhagen University Hospital Roskilde, Denmark ** Department of Clinical Epidemiology, Aarhus University Hospital, Denmark # Department of Gastroenterology, Copenhagen University Hospital Herlev, Denmark †† Institute of Health, Science and Technology, Aalborg University, Aalborg, Denmark ‡ National Institute of Public Health, University of Southern Denmark, Copenhagen, Denmark. †

Background Inflammatory bowel disease (IBD) is associated with increased cardiovascular risk. We examined the effect of active IBD on major adverse cardiovascular outcomes after myocardial infarction (MI). Methods and results We identified 86,790 first-time MI patients 2002-2011, in nationwide registries. Activity of IBD was categorized in stages of flare, persistent activity or remission. Short-term mortality was estimated in a logistic regression model, whereas risks of recurrent MI, all-cause mortality, and a composite of recurrent MI, cardiovascular death, and stroke were estimated by Cox regressionmodels. The odds ratio of death during hospitalization or within seven days of discharge (n=11,502) corresponded to 1.74 (95% [confidence interval] CI 1.09-2.77) for patients in IBD flares, 1.25 (95% CI 0.71-2.20) for persistent activity, and 0.92 (95% CI 0.74-1.14) for remission. Among 75,288 patients, including 892 with IBD, alive seven days after discharge, 9,730 had recurrent MI, 23,167 died, and the composite endpoint occurred in 21,722 patients during a mean follow-up of 3.9 years. Corresponding IBD-associated hazard ratios (HRs) were 1.12 (95% CI 0.95-1.38), 1.16 (95% CI 1.03-1.30), and 1.10 (95% CI 0.97-1.24), respectively. Specifically, IBD flares were associated with markedly increased risks of recurrent MI (HR 2.70 [95% CI 1.63-4.48]), all-cause mortality (HR 2.47 [95% CI 1.83-3.35]) and the composite endpoint (HR 1.80 [95% CI 1.21-2.66]), whereas no increased risk was identified in remission. Conclusion Active inflammatory bowel disease worsens prognosis after myocardial infarction, in particular in relation to flares.

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