Do hypertensive patients' beliefs about their illness and treatment ...

Journal of Human Hypertension (2001) 15, Suppl 1, S65–S68  2001 Nature Publishing Group All rights reserved 0950-9240/01 $15.00 www.nature.com/jhh

A Sub-study of the ASCOT Trial

Do hypertensive patients’ beliefs about their illness and treatment influence medication adherence and quality of life? R Horne1, J Clatworthy1, A Polmear2 and J Weinman3 1

Centre for Health Care Research, University of Brighton, 1 Great Wilkins, Falmer Campus, Brighton BN1 9PH, UK; 2Academic Unit of Primary Care, Trafford Centre for Graduate Medical Education and Research, University of Sussex, Falmer, Brighton BN1 9RY, UK; 3Division of Psychiatry and Psychology, Guy’s King’s and St Thomas’ School of Medicine, 5th Floor, Thomas Guy House, Guys Campus, London SE1 9RT, UK

Keywords: illness beliefs; medication beliefs; adherence; quality of life

Introduction This study will investigate the relationship between patients’ beliefs about hypertension and antihypertensive medication and how these beliefs are related to medication adherence and subjective quality of life over time. Research suggests that non-adherent behaviours fall into two broad categories: unintentional (eg, forgetfulness) and intentional (based on patient decision-making). Intentional non-adherence is often based upon maladaptive beliefs about the illness and treatment. Patients’ perceptions of their illness have also been shown to explain a significant proportion of the variance between clinical disease severity and disability. Despite the demonstrated utility of the ‘illness perceptions approach’ to understanding adherence and health status in other illnesses, few studies have tested the value of this approach in hypertension. Although the ASCOT study will compare the effects of two antihypertensive regimens on mortality and morbidity, it does not include an assessment of medication adherence or subjective quality of life. Identifying the types of beliefs that predict low adherence and poor adjustment will identify targets for an intervention to help patients develop a model of illness which facilitates a positive adjustment to hypertension and helps them get the most from their treatment. This would have benefits for both the patient and the NHS.

Correspondence: Dr Robert Horne, Centre for Health Care Research, 1 Great Wilkins, Falmer Campus, Brighton BN1 9PH, UK. E-mail: r.horne얀bton.ac.uk

Background and rationale Non-adherence to treatment is a significant barrier to the attainment of optimum outcomes in hypertension. The high medical and social costs of nonadherence and the lack of effective methods for dealing with it has stimulated renewed interest in this complex issue. Despite a plethora of research studies, a recent systematic review showed that effective interventions remain elusive.1 The reason for this disappointing result is that most interventions are applied uniformly to patients regardless of individual need. This conflicts with the available evidence, which suggests that individual patients experience a range of difficulties in managing their medication. Unintentional non-adherence may result from poor doctor–patient communication (eg, the patient fails to understand what is expected) or from lack of ability to follow the advice (eg, the patient forgets or cannot physically manage to administer the medication). Intentional non-adherence occurs when the patient knows what is required but decides not to follow this advice. Past interventions to improve adherence have usually concentrated on one aspect of this complex picture, for example by attempting to combat forgetfulness by issuing reminders. This approach is inherently limited because it addresses a single need identified in a population, whereas each individual patient has a unique profile of needs in relation to managing their medication, none of which may be met by a single standardised intervention. There is a need for a new model of care that is responsive to the needs of the individual.

Hypertensive patients’ beliefs and adherence R Horne et al

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There is accumulating evidence that lack of motivation to take the treatment often arises from mistaken beliefs about the necessity of the treatment or from concerns about the potential adverse effects.2 Often these beliefs are influenced by perceived symptoms.3 Additionally, patients’ perceptions of their illness (eg, beliefs about the causes, likely duration and consequences) have been shown to account for a significant proportion of the variance between clinical disease severity and outcome (eg, levels of disability and subjective quality of life).4 This research suggests that certain beliefs may be viewed as maladaptive in that they act as barriers to adherence or predict higher levels of disability and reduced quality of life (even when controlling for clinical severity). These findings are encouraging because they suggest that adherence and quality of life may be improved by simple interventions to correct misplaced beliefs about the illness and treatment. Despite the demonstrated utility of the ‘illness perceptions approach’ to understanding adherence and health status in other illnesses, few studies have tested the value of this approach in hypertension. Notable exceptions are two studies from the UK5 and USA.6 These studies suggest that hypertensive patients may use their medication sporadically in response to everyday symptoms (eg, headache or feeling stressed) which they attribute to their hypertension and may avoid medication because of concerns about long term adverse effects or dependence. However, both studies were small scale, qualitative studies and several outstanding questions need to be answered to help design a comprehensive intervention. For example, how do potentially erroneous beliefs develop over the course of the illness and treatment regimen? How do intentional (eg, beliefs) and unintentional (eg, forgetfulness, lack of information) factors interact to determine the patients’ medication-taking practice? Antihypertensive medication is not usually associated with symptomatic benefit and medication may even make patients feel worse. How is high adherence maintained in the absence of perceived symptomatic benefit? Do patients’ perceptions of their illness contribute to subsequent quality of life? Recent developments of validated questionnairebased methods for assessing beliefs about illness7 and treatment8 and the opportunity to access local ASCOT participants will allow us to address these questions in a quantitative study using a prospective longitudinal design.

Objectives The primary aim of this research is to provide information regarding hypertensive patients’ beliefs about their illness and treatment to health professionals in order to improve interventions designed to maintain consistent levels of adherence to treatment. The longitudinal design of the study Journal of Human Hypertension

will allow patients’ beliefs and adherence behaviour to be assessed over an 18-month period providing information on how beliefs and adherence change over time. A further aim is to clarify the relationship between patients’ perceptions of their illness and adherence to medication, and to relate these variables to both a subjective outcome measure (quality of life) and clinical outcome measures (eg, severity of hypertension, cardiovascular events). The study will address the following research questions: • What are the beliefs which hypertensive patients hold about their prescribed medication and about the range and severity of symptoms associated with their illness, its cause(s), duration, personal consequences and the degree to which it is amenable to cure and/or control? • How do patients’ beliefs about hypertension and its treatment and their adherence to medication change over an 18-month period? • To what extent is non-adherence to medication associated with illness and medication beliefs (eg, symptom perceptions and beliefs about the necessity of medication and concerns about potential adverse effects)? • To what extent are patients’ beliefs about their illness associated with their quality of life, the severity of their hypertension and with clinical outcomes?

Study methods/design Design A longitudinal design in which validated questionnaires will be used to assess hypertensive patients’ beliefs about their illness and medication, reported adherence to medication and quality of life at four intervals over 18 months. Measures of clinical status collected at each time point as part of the ASCOT study will be available. Ethics approval/consent details Ethics approval was gained from the East Sussex Brighton and Hove local research Ethics Committee on 8 April 1999. Informed consent will be obtained from all participants before entry into the sub-study. Number of participants It is estimated that 300 hypertensive participants will be recruited from the local arm of the ASCOT study. Sample size calculations were based on specific directional hypotheses derived from previous studies and using reported adherence as the main outcome measure. Inclusion/exclusion criteria All patients eligible for inclusion in the ASCOT study can be included in this sub-study, with the


exception of any with notable difficulties in understanding spoken and written English. Recruitment details Participants will be invited to take part in this substudy by the research nurses at their initial ASCOT interview or, for those patients already in the ASCOT study, at their 6 or 12-month follow-up appointment. Patients will be given a consent form and a letter explaining the purpose of the study. Consent forms will be returned to the sub-study researcher who will send each participant four questionnaires in the post over an 18-month period. Measures: Illness Perception Questionnaire (IPQ)7: An 85-item scale which provides valid and reliable measures of patients’ beliefs about the symptoms which are associated with their hypertension, and their beliefs about the cause(s), duration, and consequences of their hypertension, as well as its amenability to control and/or cure. The Beliefs about Medicines Questionnaire (BMQ)8: An 11-item validated questionnaire assessing patients’ views about the likely benefits (eg, personal beliefs about the necessity of prescribed medication) and ‘costs’ of medication (eg, beliefs about potential adverse effects as well as the difficulties of using medication). Quality of Life (Medical Outcomes Study ShortForm-36 Questionnaire (SF-36)): The SF-36 has been validated for use within UK samples and is the preferred instrument when measuring quality of life in cardiovascular diseases.9 Compliance indicators and markers: Two measures will be used: (1) Patient Report—a 10-item self-report questionnaire will be used to assess unintentional and intentional compliance with medication. This scale has been developed from the Morisky scale which has good psychometric properties and has been shown to have good predictive validity: scale scores predicted hypertensive control in an 18-month follow up study.10 (2) Tablet count—performed by ASCOT research nurses on containers returned by patients. Negative affect: The Beck Depression Inventory (BDI)11 will be used to assess negative affect. Clinical data: Data on the patients’ clinical condition will be made available to us from the central ASCOT database, including blood pressure, study end points and adverse events.

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Statistical methodology Repeated measures analysis of variance will be used to document changes in beliefs and medication adherence scores in the whole group over time. Multiple regression will be used to examine the role of beliefs in predicting reported and monitored adherence levels at 6 weeks, and at 6, 12 and 18-month follow-ups. Multiple linear regression will be used to investigate the strength of associations between reported and monitored adherence over the full follow-up period. Hierarchical multiple linear regression will be used to assess the amount of variance in quality of life that can be explained by illness beliefs, once the effect of clinical factors and baseline quality of life measures are accounted for. Time series analysis of patterns of monitored adherence over the course of the follow-up will attempt to identify useful summary statistics (eg, maximum period of poor adherence; frequency of periods of poor adherence) that categorise different patterns of adherence, which, in turn can be related to belief variables and quality of life.

Discussion This is one of the first prospective longitudinal follow-up studies to assess the role of patients’ beliefs about hypertension and its treatment on subsequent adherence and quality of life. Several limitations arise from its status as a single and relatively small-scale exploratory study. One limitation concerns the possibility of sampling bias and generalisability of our findings. It is possible that patients who agree to enter a clinical trial are more positively oriented towards medication. Moreover, the frequent attendance at ASCOT review clinics may itself encourage greater adherence. We are currently trying to address this problem by recruiting patients who are eligible for evaluation for the main ASCOT study but who do not meet the full entry criteria. This would allow us to compare beliefs and behaviour between ASCOT participants and those who volunteer for ASCOT but are excluded. The main purpose of the study is to identify the prevalence and determinants of nonadherence to antihypertensive medication. However, design of the study affords an opportunity to assess interactions between clinical variables, patient beliefs, adherence to treatment and quality of life. Unfortunately, identifying relations between adherence and quality of life and assigning causality is likely to be problematic. One reason for this is that co-morbidity is likely to be prevalent in our sample of hypertensive patients and concurrent illness may mask the effect of hypertension and antihypertensive medication on subjective quality of life. This is compounded by the fact that the treatment of hypertension is thought to result mainly in prophylactic rather than symptomatic benefit. Moreover, the Journal of Human Hypertension


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side effects of antihypertensive medication may adversely affect quality of life and reduce adherence and we agree that this is an important issue. Information about the patients’ experience and perceptions of antihypertensive medication side effects will be obtained from the following sources: • Clinical notes following patients’ clinical assessment in the ASCOT Trial. • Patients’ experience of symptoms that they attribute to medication (assessed using the Illness Perceptions Questionnaire). • Patients’ concerns about adverse effects (elicited using the Beliefs about Medicines Questionnaire). This will allow us to distinguish between the experience of side effects (as diagnosed by the doctor) and the patients’ perceptions or concerns about adverse effects. Medication side effects have the potential to influence both the primary and secondary outcome measures (adherence and quality of life). Previous research suggests that patients’ perceptions of adverse events and anticipation of future problems may lead to intentional non-adherence. We will test this in our study by investigating relations between medication concerns (assessed using the BMQ) and medication adherence. The sample size calculations are based on an estimated response rate of 70% and a subsequent completion rate of 70%. Although the study hinges on postal questionnaires, these will be supplemented by postal and telephone reminders. Similar response and completion rates have been obtained in other studies of beliefs and behaviour in cardiac patients.4 Despite these limitations we believe that the study will provide valuable and unique data. It will guide future research in adherence to medication and could inform the design of interventions to facilitate adherence to treatment.

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