Family Practice Vol. 21, No. 5 © Oxford University Press 2004, all rights reserved.
Effects of secondary prevention clinics on health status in patients with coronary heart disease: 4 year follow-up of a randomized trial in primary care
a Department of General Practice and Primary Care, University of Aberdeen, Foresterhill Health Centre, Westburn Road, Aberdeen AB25 2AY, b Clinical Psychology Department, Clarkseat Building, Royal Cornhill Hospital, Aberdeen AB25 2ZH and c Westburn Centre, Westburn Road, Aberdeen AB25 2XG, UK
E-mail: p.murchie{at}abdn.ac.uk
Received 29 August 2003; Revised 16 February 2004; Accepted 17 May 2004.
Murchie P, Campbell NC, Ritchie D, Deans HG and Thain J. Effects of secondary prevention clinics on health status in patients with coronary heart disease: 4 year follow-up of a randomized trial in primary care. Family Practice 2004; 21: 567–574.
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Abstract |
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Background. The long-term effects of disease management programmes for coronary heart disease on health status are unknown. In a randomized trial of nurse-led secondary prevention clinics, we found significantly improved health status at 1 year. Participants were followed-up again at 4 years to determine if improvements had been sustained.
Objective. Our aim was to evaluate the effects on health of nurse-led clinics for the secondary prevention of coronary heart disease in primary care.
Methods. A total of 1343 patients with coronary heart disease were randomized to nurse-led secondary prevention clinics or usual care, with follow-up at 1 and 4 years by review of medical case notes and national data sets, and postal questionnaires. The study involved a stratified, random sample of 19 general practices in north-east Scotland. Health status was measured by the SF-36 questionnaire, chest pain by the angina TyPE specification and anxiety and depression by the hospital anxiety and depression scale.
Results. At 1 year, there were significant improvements in five of eight SF-36 domains (all functioning scales, pain and general health) in patients randomized to clinics. Role limitations attributed to physical problems improved the most [adjusted difference 8.52, 95% confidence interval (CI) 4.16–12.9]. At 4 years, the intervention group scored higher than control in all domains, but differences were no longer significant. At 1 year, fewer patients in the intervention group reported worsening chest pain (odds ratio 0.59, 95% C1 0.37–0.94). At 4 years, there were no significant differences between the proportion of intervention or control group patients who reported chest pain in the last week or who reported worsening chest pain. No significant effects were observed on anxiety or depression at 1 or 4 years.
Conclusion. We have demonstrated previously a significantly greater survival in attendees at nurse-led secondary prevention clinics. Despite this, improvements in health status achieved in the first year of the study were reduced at 4 years. The case for nurse-led clinics remains strong, but further research is required on ways to optimize current health status.
Keywords. Coronary heart disease, primary care, secondary prevention.
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Introduction |
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GPs are ideally placed to target patients with existing coronary heart disease.1 Strong evidence exists to support this strategy, and a recent meta-analysis of 12 randomized controlled trials of disease management programmes of patients with coronary heart disease concluded that such programmes improve processes of care, reduce admissions to hospital and enhance quality of life or functional status.2
Eight trials evaluated effects on functional status or quality of life and, in five, scores were better in the intervention group. Two trials found no significant improvement in quality of life or functional status, but in both the follow-up period was 6 months or less.3,4 The other three trials employed a follow-up period of 12 months and demonstrated significant short-term improvements in quality of life or functional status.5,6,7
The longer and medium term effects of disease management programmes on quality of life or functional status remain unknown. We conducted one of the randomized trials included in the recent systematic review and found that, at 1 year, nurse-led secondary prevention clinics in primary care significantly improved health-related quality of life.7,8 We previously have reported that the improvements in uptake of secondary prevention translated after 4.7 years into reduced deaths and coronary event rates.9 There remains the question, however, of whether health in survivors was improved or unchanged by clinic attendance. We now report a 4 year follow-up study which aimed to evaluate whether improvements in health status were sustained at 4 years.
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Methods |
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Details of recruitment, randomization and the intervention have been reported previously.7,8 Briefly, 1343 randomly selected patients with a working diagnosis of coronary heart disease, but without terminal illness or dementia and not housebound, were recruited from 19 randomly selected general practices in north-east Scotland. Participants were randomized by NC (by individual after stratification for age, sex and practice), using tables of random numbers, to intervention or control groups.
Participants in the intervention group were invited to attend secondary prevention clinics at their general practice, during which their symptoms and treatment were reviewed, use of aspirin promoted, blood pressure and lipid management reviewed, lifestyle factors assessed and, if appropriate, behavioural change negotiated. Follow-up was according to clinical circumstances (2–6 monthly was advised in the protocol). Participants in the control group received usual care from their GP. After 1 year, data were collected on uptake of secondary prevention and participants' health. Findings were fed back to participating general practices who decided their own policies on running clinics.
After 4 years, the original participants were traced via their general practices or, for those who had moved within Scotland, using Health Board records. For those who left Scotland, follow-up ceased when their general practice case notes were transferred out of the country.
Data on health and symptoms were collected before intervention, at 1 year and at 4 years by postal questionnaire. The SF-36 health survey questionnaire is a general outcome measure that uses eight scales to assess three aspects of health. It has been validated for use in the UK.10 The Angina TyPe specification is designed for use with the SF-36 questionnaire and assesses presence, frequency and course of chest pain.11 The hospital anxiety and depression scale is a widely used instrument to assess mental state which has also been validated previously.12
The original trial was designed to detect differences in secondary prevention.7 A sample size of 1300 at baseline was projected to give at least 808 respondents, which would be sufficient to detect five point ‘clinically and socially relevant’ differences in all SF-36 domains.7 As now recognized, the ‘role physical‘ and ‘role emotional’ domains of the SF-36 have a categorical distribution. On the other hand, changes in score are normally distributed and analyses were conducted accordingly.13 Our primary analysis was on an intention to treat basis using SPSS for Windows release 9.0.0. Binary outcomes were analysed using logistic regression, and ordinal categories and continuous outcomes using multiple linear regression, with adjustments for age, sex, practice and baseline performance.
We also performed a secondary analysis by actual exposure to clinics. Four categories were assigned: no exposure, attended for up to 1 year, attended for between 1 and 3 years, and attended for >3 years.9
The study was effectively open because practice staff who ran the clinics knew which patients were in the intervention group. Questionnaire data were entered blind to group allocation. The study was approved by Grampian Health Board and University of Aberdeen Joint Ethics Committee.
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Results |
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Intervention and control groups were well matched for age, sex and practice characteristics at baseline (Table 1). Mean follow-up was 4.7 years. Of the 1343 original participants, 1173 completed a postal questionnaire at 1 year (Fig 1). At 4 years, 228 had died and 16 had left Scotland. Of the 1098 surviving participants, 42 were excluded from the postal questionnaire because of dementia or terminal illness. The questionnaire was completed by 961 of the remaining 1056 participants (91%). Fewer participants in the intervention group dropped out largely due to fewer deaths (Fig. 1). Responders to the final questionnaire had significantly better scores in six out of eight domains of the SF-36 and were significantly less depressed at baseline compared with those who dropped out (Table 2).
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At 1 year, the study practices rolled out the clinics to all of their patients with coronary heart disease. During the first year of the study, 551 of 673 (82%) participants in the intervention group attended a secondary prevention clinic at least once. At follow-up, by which time 16 practices were running clinics and three stopped, 493 of 564 (87%) surviving in the intervention group had attended at least one secondary prevention clinic but, due to crossover, 296 control group patients (56%) had also attended at least one clinic.
Health status deteriorated in both groups over 4 years (Table 3). At 1 year, the intervention group scored significantly better in five out of eight domains. At 4 years, the intervention group scored higher than controls in all domains, but differences were no longer significant. The difference in the physical domain of the SF-36 was borderline significant but the actual difference observed was small in clinical terms.
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Table 4 shows the numbers of patients in the intervention and control groups, with chest pain, worsening chest pain and who were anxious and depressed at 1 year and at 4 years. The adjusted odds ratios show that at 1 year, significantly fewer of the intervention group reported worsening chest pain. At 4 years, there were no significant differences between groups in reported chest pain, worsening chest pain anxiety or depression.
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When changes in SF-36 were compared by exposure to clinics, adjusting for age, sex, baseline performance and general practice characteristics, we found few significant differences. The ‘role physical‘ score improved most in patients who attended clinics for between 1 and 3 years, and there was a trend for improvements in ‘energy’ score with increasing exposure to clinics, although the magnitude of the increase was small (Table 5). The odds of depression were lower in patients exposed to clinics, but there were no significant differences in anxiety or chest pain (Table 6).
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Discussion |
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Previously, we reported that patients with established coronary heart disease had significantly improved health, following 1 year of attendance at secondary prevention clinics.7 This follow-up study assessed the longer-term effects of clinics on health status at 4 years. At 4 years, improvements in health status achieved in the first year of the clinics were reduced. The intervention group had better scores in all domains of the SF-36, but differences between groups were no longer significant. There were no longer any statistically significant differences between groups in the numbers of patients reporting chest pain, worsening chest pain, anxiety or depression.
The main limitation of this follow-up study was the crossover of participants from control group to the intervention group after the original trial year. At 4 year follow-up, 298 (56%) of the original control group had attended at least one secondary prevention clinic. Clearly this creates difficulties in interpretation. Crossover is likely to have reduced any differences between groups in the main intention to treat analysis. A cluster randomized design may have partly ameliorated this, but to retain the same power we have calculated that 3100 patients from 44 general practices would have been required, with consequent practical difficulties.14 Furthermore, we felt ethically obliged to report the 1 year benefits to all practices, so crossover is likely to have occurred whatever the unit of randomization.
This follow-up trial built on the findings of the original randomized trial which was well conducted.1,15,16 By extending the follow-up period to >4 years, we have remedied one of the main limitations of the original trial, the relatively short follow-up period of 1 year. The trial used random samples of practices and patients, response rates throughout were high and very few patients were lost to foliow-up. We believe that the results are generalizable, certainly within north-east Scotland, although this population may be more static than found in other areas of the UK.
A recent systematic review of 12 randomized trials of secondary prevention strategies for coronary heart disease in a variety of settings concluded that they improved processes of care and risk factors.2 Eight trials evaluated quality of life or functional status, and in five3–7 scores were better in the intervention arm, although statistical significance was reached in only three cases. In most of the included trials, the follow-up period was short (
1 year) and it was in the trials with longer follow-up periods (up to 1 year) that significant improvements were demonstrated. One trial included in the systematic review measured quality of life using the Nottingham Health Profile and, at 2 year follow-up, coronary heart disease patients who had received health promotion performed significantly better.17,18 When these participants were followed-up at 5 years, there were no longer any significant differences between groups in restriction of activities.19 These results correspond with our own 1 and 4 year results and, taken together, suggest that the short-term benefits in health status produced by 1 or 2 year secondary prevention interventions are not sustained in the longer term.
The general decline in physical health and increase in anxiety and depression at 4 year follow-up observed in both groups would be expected due to the effects of ageing,20 but there are three main explanations as to why the differences between the intervention and control groups observed at 1 year are no longer significant at 4 year follow-up.
First, crossover occurred between 1 and 4 years, and 56% of control group patients attended clinics. This may have improved health in the control group such that intervention effects were obscured in the intention to treat analysis. This is not, however, borne out when the analysis by exposure to treatment is considered.
Secondly, follow-up was less complete in the control group, largely due to their higher death rate that may have produced bias in the final samples. For example, less fit members of the control group were more likely to have died,21 disguising any long-term improvements in physical health produced by the intervention, with less fit members of the intervention group surviving due to optimized secondary prevention as we have reported previously.9 Amongst the survivors, there may also have been a ‘sick quitter effect’, and this was also slightly higher in the control group (81 versus 72).
If these two explanations are accepted, then a sustained benefit to physical health from attending secondary prevention clinics for a year cannot be excluded. In this context, it is interesting that the difference in physical functioning on the SF-36 between groups at 4 years just fails to reach statistical significance.
On the other hand, the final possible explanation is that short-term secondary prevention programme (1 year) do not produce sustained long-term improvements in health status. This corresponds to the conclusions of the Belfast study.19 In addition, the intervention appears to have had no significant effect on anxiety and depression at 1 or 4 years. Although it is encouraging that secondary prevention clinics do not increase anxiety and depression in patients with coronary heart disease, the non-specific psychological support provided by the clinics does not improve mental well-being.
Our findings reveal that people with coronary heart disease have relatively poor quality of life, compared with an unselected population,10 and that this deteriorates further over time. Nurse-led clinics can improve secondary prevention and reduce deaths, but further research is required to identify strategies that can produce definite long-term improvements in health status in patients with established coronary heart disease.
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Declaration |
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Funding: This study was funded by the Chief Scientist Office at the Scottish Executive.
Ethical Approval: Full ethical approval for the follow-up study was granted by the Grampian Research Ethics Committee on 24th May 1999. (full approval was given by GREC for the original one year RCT on 30th January 1994).
Conflicts of interest: None declared.
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Acknowledgments |
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We would like to thank staff at all the general practices who participated in the study, especially the health visitors, practice nurses and district nurses who ran the clinics. Participating general practices were Aboyne Medical Practice, Ardach Practice, Dr Crowley, Danestone Medical Practice, Elmbank Group, Dr Grieve and Partners, Kemnay Medical Practice, Kincorth Medical Practice, King Street Medical Practice, The Laich Medical Practice, Dr Mobbs and Partners, Drs Mackie and Kay, Old Machar Medical Practice, Rubislaw Medical Group, Seafield Medical Practice, Skene Medical Practice, Spa-Well Medical Group, Turriff Medical Practice and Victoria Street Medical Group.
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