Alimentary Pharmacology & Therapeutics
Incidence and case fatality for acute pancreatitis in England: geographical variation, social deprivation, alcohol consumption and aetiology – a record linkage study S. E. ROBERTS*, J. G. WILLIAMS*, D. MEDDINGS & M. J. GOLDACRE
*School of Medicine, Swansea University, Swansea, UK; Unit of Health-Care Epidemiology, University of Oxford, Oxford, UK Correspondence to: Dr S. E. Roberts, School of Medicine, Swansea University, Singleton Park, Swansea SA2 8PP, UK. E-mail:
[email protected]
Publication data Submitted 4 March 2008 First decision 24 March 2008 Resubmitted 15 July 2008 Accepted 15 July 2008 Epub Accepted Article 18 July 2008
SUMMARY Background Regional studies in the UK indicate that the incidence of acute pancreatitis increased from the 1940s to the 1990s, while case fatality fell until the 1970s but has levelled-off since. Aims To establish incidence and case fatality for acute pancreatitis in England from 1998 to 2003, to study geographical variation and recent trends in incidence and to study associations with social deprivation and alcohol consumption. Methods Use of national record linkage of in-patient and mortality data for 52 096 people. Results Overall incidence was 22.4 per 100 000 population, increasing by 3.1% annually, with largest increases for women aged under 35 years (11% per year) and for men aged 35 to 45 (5.6%). Incidence was higher in northern regions than in southern regions and in areas with high social deprivation and binge drinking. Case fatality was 6.7% at 60 days, higher for alcoholic than gallstones aetiology and was associated with social deprivation and geography. Conclusions Acute pancreatitis is a growing problem in England, particularly among younger women. The findings indicate strongly that alcohol consumption is the main reason for recent increases in incidence, the higher incidence in socially-deprived areas and for the lack of recent improvement in prognosis. Aliment Pharmacol Ther 28, 931–941
ª 2008 The Authors Journal compilation ª 2008 Blackwell Publishing Ltd doi:10.1111/j.1365-2036.2008.03809.x
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INTRODUCTION
METHODS
The incidence of acute pancreatitis has increased sharply in the UK in the last 50 years. A Scottish national study reported a ten-fold increase in men and a fourfold increase in women from 1961 to 1985,1 a study of the Oxford region reported a two-fold increase from 1963–1974 to 1987–1998,2 and a national English study reported a 34% increase from 1989 to 1999.3 Incidence rates reported from recent studies in England and Wales (10 to 20 per 100 000 population)2–4 are typically much lower than rates of 20 to 70 per 100 000 reported for northern countries such as Scandinavia,5–8 Germany,9 Iceland10 Scotland1, 11 and the USA,12 but are more comparable with rates reported for the Netherlands,13, 14 and Ireland.15 However, little is known about geographical variation in the incidence of acute pancreatitis within England. Acute pancreatitis is sometimes caused by heavy alcohol consumption, with most recent studies reporting alcohol as the dominant aetiological factor in about 15–40% of cases diagnosed in Britain,4, 16–18 and in about 25–60% of cases diagnosed elsewhere in Europe.6, 10, 19–21 Although alcohol-related gastrointestinal disorders such as liver cirrhosis and upper gastrointestinal haemorrhage are associated strongly with social class,22–24 very little has been reported on the association between acute pancreatitis and socioeconomic factors. A major study in the Nottingham region found no association with social class, but reported increased incidence in residential areas with particularly hard drinking water.25 Based mainly on regional studies in the UK, case fatality had fallen over time to about 8–10% by the 1970s.1, 2, 26, 27 However, there appears to have been little further reduction in mortality in the last 25 years.2, 4, 11, 17, 28, 29 There is little reported on variation in case fatality geographically across England or according to socioeconomic factors or alcohol consumption. The first aims of this study were to establish the incidence and case fatality for acute pancreatitis in England. Further aims were to investigate variation in incidence and case fatality geographically across England and according to social deprivation and alcohol consumption, to assess trends over time in incidence, to identify cases attributed to the two main aetiologies - alcohol and gallstones - and to investigate the relationship between aetiology and case fatality, geography and social deprivation.
To identify the incidence of acute pancreatitis in England, we used the recently developed English national record linkage study. This incorporates abstracts of all in-patient admissions in NHS hospitals in England that, for each individual, are systematically brought together and linked to ONS mortality data using record linkage. Thus, we are able to identify multiple admissions for the same people, to measure incidence in terms of people and new attacks of acute pancreatitis rather than just in terms of episodes or hospital admissions for care. Using linkage, we are also able to identify deaths following discharge from hospital as well as in-hospital deaths when establishing case fatality. The International Classification of Diseases tenth revision (ICD-10) code used for acute pancreatitis is K85. We selected only those admissions where acute pancreatitis was recorded as the principal diagnosis and included all sources of admission. The study period included admissions during the five years from April 1st 1998 to March 31st 2003. Readmissions may follow a first admission as a complication of the original attack; but acute pancreatitis is often characterized by separate, new attacks, each requiring hospitalization. We therefore included subsequent admissions for acute pancreatitis for each individual, assuming them to be a new ‘case’ of acute pancreatitis, if they occurred at least 60 days after a previous admission. Thus, our measure of incidence is of separate attacks of acute pancreatitis. We use the term ‘admission’ to refer to every hospitalization for acute pancreatitis, ‘case’ to refer to every separate attack and ‘people’ to refer to each individual regardless of whether he ⁄ she contributed one or more cases.
Geographical location, social deprivation and alcohol consumption When investigating geographical variation in acute pancreatitis, we measured incidence, firstly in each of the nine Government Office (GO) regions of England and, secondly, in each of the 352 English local authority areas. To measure social deprivation, we used the Index of Multiple Deprivation (IMD) score, based on residential postcode and compiled at the local authority level for 2004.30 Local authorities were ranked according to their IMD score and were categorized into ª 2008 The Authors, Aliment Pharmacol Ther 28, 931–941 Journal compilation ª 2008 Blackwell Publishing Ltd
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quintiles, with Quintile I representing the 20% of most deprived local authorities and Quintile V the 20% of least deprived local authorities. Alcohol consumption was measured using the synthetic estimate of binge drinking,31 developed by the North West Public Health Observatory, which was assigned at the local authority level. This was defined as the percentage of people who had consumed eight or more units of alcohol – or six or more for women on at least one day during the previous week. Local authorities were also grouped into quintiles according to their measures of binge drinking, Quintile A with the highest levels of binge drinking and Quintile E with the lowest levels.
Aetiology of acute pancreatitis The two main aetiologies of acute pancreatitis – gallstones and alcohol – were distinguished as follows. Gallstones-acute pancreatitis was defined as a principal diagnosis of biliary acute pancreatitis (ICD-10 code = K85.1) or as a secondary diagnosis of cholelithiasis (K80) or cholecystitis (K81) in a case with a principal diagnosis of acute pancreatitis of unspecified aetiology (K85.9). Alcohol-induced pancreatitis was defined as a principal diagnosis of alcohol-induced acute pancreatitis (K85.0) or as a secondary diagnosis (in a case coded as unspecified acute pancreatitis) of one of 11 conditions that are entirely because of alcohol and thus have an alcohol attribution fraction of one.32 These are alcoholic pseudo-induced Cushing’s syndrome (E244), mental and behavioural disorders caused by use of alcohol (F10), degeneration of nervous system caused by alcohol (G312), alcoholic polyneuropathy (G612), alcoholic myopathy (G721), alcoholic cardiomyopathy (I426), alcoholic gastritis (K292), alcoholic liver disease (K70), ethanol poisoning (T510), methanol poisoning (T511) and accidental poisoning by and exposure to alcohol (X45).
Incidence Incidence rates were calculated using hospitalizations for acute pancreatitis as numerators and the corresponding resident populations at risk as denominators. To adjust for age and gender differences in the populations of different geographical regions and social deprivation categories, we used the indirect method of standardization and the total English population as the standard. Pearson’s correlation coefficients were used ª 2008 The Authors, Aliment Pharmacol Ther 28, 931–941 Journal compilation ª 2008 Blackwell Publishing Ltd
to measure correlations between incidence rates for acute pancreatitis and other measures (e.g. IMD score, synthetic estimates of binge drinking) in the local authorities. Geographical Information Systems (GIS) were used to produce maps of incidence rates across England.
Case fatality Case fatality rates (CFRs) were calculated at both 30 days and 60 days. Case fatality at 30 days captures most deaths resulting from a particular attack and its possible complications, while not including many unrelated deaths. Case fatality at 60 days would capture some additional deaths from acute pancreatitis and its complications in the longer term, but increases the risk of including some unrelated deaths. CFRs were calculated using hospital admissions for acute pancreatitis as the denominators and subsequent deaths from any cause as the numerators. To age adjust case fatality (expressed as odds ratios) for geographical regions and social deprivation quintiles, we used logistic regression. The chi-square test for trend was used to assess the significance of associations between social deprivation and binge drinking quintiles with case fatality and the chi-square test for heterogeneity was used to assess the significance of associations between GO region and case fatality.
RESULTS During the five-year study period, using our inclusion criteria to define separate attacks of acute pancreatitis, there were 55 960 cases. Of these, 443 (0.8%) were for people who were not resident in England and 302 (0.5%) were for people without a valid place of residence recorded on the discharge record. Excluding these, there were 55 215 cases in all (incidence rate = 22.4 per 100 000 population per year), which related to 52 096 people. 28 543 of the cases were for men (incidence rate = 23.7 per 100 000) and 26 672 were for women (incidence rate = 21.2).
Trends in incidence The overall incidence of acute pancreatitis in England increased significantly by 12.3% over the five year study period from 20.9 per 100 000 (95% CI = 20.6– 21.4) in 1998 ⁄ 99 to 23.5 (95% CI = 23.1–23.9) in 2002 ⁄ 03 (Table 1). The mean annual increase was
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Table 1. Incidence rates for acute pancreatitis (per 100 000 population) according to age group and gender, with corresponding average annual percentage increases from 1998 to 2003
Age group Men
