Trends in rates of different forms of diagnosed coronary heart disease
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《英国医生杂志》
1 Department of Primary Care and Population Sciences, Royal Free and University College Medical School, London NW3 2PF, 2 Department of Community Health Sciences, St George's Hospital Medical School, London SW17 ORE
Correspondence to: F Lampe f.lampe@pcps.ucl.ac.uk
Objective To examine trends over time in rates of different forms of diagnosed coronary heart disease among British men, during a period in which mortality due to coronary heart disease has been declining.
Design Prospective cohort study covering the period 1978-80 to 1998-2000.
Participants 7735 men, aged 40-59 at entry, randomly selected from one general practice in each of 24 British towns.
Main outcome measures Trends in the rates of major coronary events, first diagnosed angina and first diagnosed coronary heart disease (any fatal or non-fatal documented event or diagnosis). Events were ascertained from NHS central registers and reviews of medical records from general practices.
Results Over the 20 year period, 1561 major coronary events occurred; 1087 and 1816 men had new diagnoses of angina and coronary heart disease, respectively. The age adjusted annual relative changes were -3.6% (95% confidence interval -4.8% to -2.4%, P < 0.001) for all major coronary events, 2.6% (1.1% to 4.0%, P < 0.001) for first diagnosed angina and -0.8% (-1.8% to 0.3%, P = 0.18) for first diagnosed coronary heart disease. The fall in major coronary events occurred across all categories of event (fatal and non-fatal, first and recurrent). Similarly, first diagnosed angina increased for both uncomplicated angina and angina after myocardial infarction. The age adjusted annual relative change in case fatality at 28 days of first major coronary events was -1.4% (-3.1% to 0.4%, P = 0.12).
Conclusions Among British middle aged men, a substantial decline in the rate of major coronary events over the past two decades seems to have been largely offset by an increase in the incidence of diagnosed angina. Overall there was little change in the incidence of first diagnosed coronary heart disease. A continuing need exists for resources and services for coronary heart disease in general, and for new angina in particular.
Since the late 1970s, rates of coronary heart disease death in the United Kingdom have fallen by more than 50%.1 Data from the monitoring trends and determinants in cardiovascular disease (MONICA) studies2 and a previous report from the British Regional Heart Study3 showed that this trend has been due in part to a fall in the rate of occurrence of new major coronary events. However, despite increasing evidence of falling incidences of myocardial infarction in Britain and other countries, little is known about trends in rates of "lesser" diagnoses, particularly angina, a condition that makes a large contribution to the total incidence of diagnosed coronary heart disease.4 In Britain, angina is commonly diagnosed and managed in primary care,5 6 and studies based on cases in patients admitted to hospital may not present a complete picture of medically recognised disease in the population. Using information from general practice medical record reviews we examined trends in rates of different forms of diagnosed coronary heart disease in the British Regional Heart Study during 20 years of follow-up, from 1978-80 to 1998-2000. In particular we assessed whether trends in the incidence of diagnosed angina and diagnosed coronary heart disease overall have followed a similar pattern to trends observed for rates of major coronary events. Changes in rates of different forms of diagnosed coronary heart disease have implications for prevention policy and health provision.
Methods
The British Regional Heart Study is a prospective study of 7735 men aged 40-59 years at baseline (1978-80), who were randomly selected from one general practice in each of 24 British towns.7 The sample includes all major geographical regions in Britain and is representative of the male population in terms of social class distribution. Information from participants' questionnaires at study entry was used to ascertain diagnoses of pre-existing coronary heart disease.8 Participants were followed over 20 years through NHS central registers and regular reviews of medical records in general practices (including hospital and clinic correspondence) for death due to coronary heart disease, first and recurrent definite myocardial infarctions, first and recurrent possible myocardial infarctions, and first diagnosis of angina.9 About 1% of men have been lost to follow-up.
End points
We examined trends in rates of diagnosed (medically recorded) coronary heart disease only. End points are defined in table 1. We considered three main categories: all major coronary events (subdivided into death due to coronary heart disease and non-fatal definite myocardial infarction, and also into first major coronary event and recurrent major coronary events); first diagnosed angina (subdivided into uncomplicated angina, and angina post myocardial infarction); and first diagnosed coronary heart disease (any fatal or non-fatal documented coronary event or diagnosis). Three end points—all major coronary events, non-fatal definite myocardial infarction, and recurrent major coronary events—include multiple recurrent events from individual subjects, whereas the remainder are restricted to the first ever events only.
Table 1 Definitions of coronary end points and numbers of events occurring among 7735 men during 20 year follow-up
Statistical analysis
We ascertained numbers of events and person years at risk during four exact five year follow-up periods from each subject's baseline assessment date: 1978-80 to 1983-5, 1983-5 to 1988-90, 1988-90 to 1993-5, and 1993-5 to 1998-2000. We used Poisson regression to estimate trends in event rates, with date of follow-up period as a continuous covariate and person time of follow-up as an offset. We used quadratic or cubic polynomials as necessary to adjust for age, in order to account for the non-linear association over the age range included in analyses. We used generalised estimating equations with an autoregressive correlation structure to account for recurrent events from individual subjects (using SAS, release 8.02, SAS Institute, Cary, NC, USA). Accounting for clustering owing to initial town of selection had little effect on standard errors of trend estimates; we present unadjusted results. Trends are expressed as the average annual relative change in event rate with 95% confidence interval. For example, a rate ratio of 0.970 is presented as a relative rate change of -3.0%. We also examined trends in the case fatality of first major coronary events (percentage fatal within 28 days), using Poisson regression (as this provides the risk ratio rather than the odds ratio10), with date of event and age at event as covariates. We used tests of interaction to assess social class differences in trends, with each subject's social class classified as "non-manual" or "manual," according to occupation at entry into the study.
Results
Figure 1 shows the occurrence of coronary events and diagnoses among the 7735 men during 20 years of follow-up; total numbers of events in each category are given in table 1. Overall there were 1561 major coronary events; 1087 and 1816 men had new diagnoses of angina and coronary heart disease respectively. Figure 2 shows age specific trends for the three main end points. Table 2 gives age adjusted estimates of annual trends over the 20 year period, for all event rates, presented as relative percentage changes. The rate of major coronary events fell substantially over the period by an average of 3.6% per year. The decline occurred for both fatal and non-fatal major coronary events (although it was greater for fatal events), and for both first and recurrent major coronary events (being of similar magnitude in each case). In contrast to rates of major coronary events, the rate of first diagnosed angina increased during the 20 year period, by an average of 2.6% per year. This increase was apparent for uncomplicated angina and angina diagnosed after myocardial infarction, but it was larger for angina diagnosed after myocardial infarction. Because of the opposing trends in major coronary events and angina, the rate of first diagnosed coronary heart disease changed little over the 20 year period. Trend estimates for the last 10 year period of follow-up (1988-90 to 1998-2000) are also given in table 2 for the three main end points. These indicate the same pattern of opposing trends for major coronary events and angina, and no clear change in the rate of first diagnosed coronary heart disease. Of all 1141 first major coronary events, 492 were fatal within 28 days. The average annual decline in case fatality at 28 days of first major coronary events was moderate and non-significant (relative change in risk -1.4, 95% confidence interval -3.1 to 0.4, P = 0.12 over the 20 year period).
Fig 1 Occurrence of coronary events among 7735 men during 20 years of follow-up
Fig 2 Rates of coronary events (per 1000 person years) by calendar period and age group at start of period
Table 2 Age adjusted estimates of annual relative percentage changes in rates of coronary events
The rate of major coronary events fell among men from both manual and non-manual social class groups (annual changes -3.3% for manual and -4.6% for non-manual), and the rate of diagnosed angina increased (annual changes 2.6% and 2.7%, respectively) over the 20 year period. We found no evidence that the magnitude of these trends differed according to social class group (interaction tests: P = 0.31 for major coronary events and P = 0.99 for diagnosed angina).(Fiona C Lampe, lecturer1, Richard W Morr)
Correspondence to: F Lampe f.lampe@pcps.ucl.ac.uk
Objective To examine trends over time in rates of different forms of diagnosed coronary heart disease among British men, during a period in which mortality due to coronary heart disease has been declining.
Design Prospective cohort study covering the period 1978-80 to 1998-2000.
Participants 7735 men, aged 40-59 at entry, randomly selected from one general practice in each of 24 British towns.
Main outcome measures Trends in the rates of major coronary events, first diagnosed angina and first diagnosed coronary heart disease (any fatal or non-fatal documented event or diagnosis). Events were ascertained from NHS central registers and reviews of medical records from general practices.
Results Over the 20 year period, 1561 major coronary events occurred; 1087 and 1816 men had new diagnoses of angina and coronary heart disease, respectively. The age adjusted annual relative changes were -3.6% (95% confidence interval -4.8% to -2.4%, P < 0.001) for all major coronary events, 2.6% (1.1% to 4.0%, P < 0.001) for first diagnosed angina and -0.8% (-1.8% to 0.3%, P = 0.18) for first diagnosed coronary heart disease. The fall in major coronary events occurred across all categories of event (fatal and non-fatal, first and recurrent). Similarly, first diagnosed angina increased for both uncomplicated angina and angina after myocardial infarction. The age adjusted annual relative change in case fatality at 28 days of first major coronary events was -1.4% (-3.1% to 0.4%, P = 0.12).
Conclusions Among British middle aged men, a substantial decline in the rate of major coronary events over the past two decades seems to have been largely offset by an increase in the incidence of diagnosed angina. Overall there was little change in the incidence of first diagnosed coronary heart disease. A continuing need exists for resources and services for coronary heart disease in general, and for new angina in particular.
Since the late 1970s, rates of coronary heart disease death in the United Kingdom have fallen by more than 50%.1 Data from the monitoring trends and determinants in cardiovascular disease (MONICA) studies2 and a previous report from the British Regional Heart Study3 showed that this trend has been due in part to a fall in the rate of occurrence of new major coronary events. However, despite increasing evidence of falling incidences of myocardial infarction in Britain and other countries, little is known about trends in rates of "lesser" diagnoses, particularly angina, a condition that makes a large contribution to the total incidence of diagnosed coronary heart disease.4 In Britain, angina is commonly diagnosed and managed in primary care,5 6 and studies based on cases in patients admitted to hospital may not present a complete picture of medically recognised disease in the population. Using information from general practice medical record reviews we examined trends in rates of different forms of diagnosed coronary heart disease in the British Regional Heart Study during 20 years of follow-up, from 1978-80 to 1998-2000. In particular we assessed whether trends in the incidence of diagnosed angina and diagnosed coronary heart disease overall have followed a similar pattern to trends observed for rates of major coronary events. Changes in rates of different forms of diagnosed coronary heart disease have implications for prevention policy and health provision.
Methods
The British Regional Heart Study is a prospective study of 7735 men aged 40-59 years at baseline (1978-80), who were randomly selected from one general practice in each of 24 British towns.7 The sample includes all major geographical regions in Britain and is representative of the male population in terms of social class distribution. Information from participants' questionnaires at study entry was used to ascertain diagnoses of pre-existing coronary heart disease.8 Participants were followed over 20 years through NHS central registers and regular reviews of medical records in general practices (including hospital and clinic correspondence) for death due to coronary heart disease, first and recurrent definite myocardial infarctions, first and recurrent possible myocardial infarctions, and first diagnosis of angina.9 About 1% of men have been lost to follow-up.
End points
We examined trends in rates of diagnosed (medically recorded) coronary heart disease only. End points are defined in table 1. We considered three main categories: all major coronary events (subdivided into death due to coronary heart disease and non-fatal definite myocardial infarction, and also into first major coronary event and recurrent major coronary events); first diagnosed angina (subdivided into uncomplicated angina, and angina post myocardial infarction); and first diagnosed coronary heart disease (any fatal or non-fatal documented coronary event or diagnosis). Three end points—all major coronary events, non-fatal definite myocardial infarction, and recurrent major coronary events—include multiple recurrent events from individual subjects, whereas the remainder are restricted to the first ever events only.
Table 1 Definitions of coronary end points and numbers of events occurring among 7735 men during 20 year follow-up
Statistical analysis
We ascertained numbers of events and person years at risk during four exact five year follow-up periods from each subject's baseline assessment date: 1978-80 to 1983-5, 1983-5 to 1988-90, 1988-90 to 1993-5, and 1993-5 to 1998-2000. We used Poisson regression to estimate trends in event rates, with date of follow-up period as a continuous covariate and person time of follow-up as an offset. We used quadratic or cubic polynomials as necessary to adjust for age, in order to account for the non-linear association over the age range included in analyses. We used generalised estimating equations with an autoregressive correlation structure to account for recurrent events from individual subjects (using SAS, release 8.02, SAS Institute, Cary, NC, USA). Accounting for clustering owing to initial town of selection had little effect on standard errors of trend estimates; we present unadjusted results. Trends are expressed as the average annual relative change in event rate with 95% confidence interval. For example, a rate ratio of 0.970 is presented as a relative rate change of -3.0%. We also examined trends in the case fatality of first major coronary events (percentage fatal within 28 days), using Poisson regression (as this provides the risk ratio rather than the odds ratio10), with date of event and age at event as covariates. We used tests of interaction to assess social class differences in trends, with each subject's social class classified as "non-manual" or "manual," according to occupation at entry into the study.
Results
Figure 1 shows the occurrence of coronary events and diagnoses among the 7735 men during 20 years of follow-up; total numbers of events in each category are given in table 1. Overall there were 1561 major coronary events; 1087 and 1816 men had new diagnoses of angina and coronary heart disease respectively. Figure 2 shows age specific trends for the three main end points. Table 2 gives age adjusted estimates of annual trends over the 20 year period, for all event rates, presented as relative percentage changes. The rate of major coronary events fell substantially over the period by an average of 3.6% per year. The decline occurred for both fatal and non-fatal major coronary events (although it was greater for fatal events), and for both first and recurrent major coronary events (being of similar magnitude in each case). In contrast to rates of major coronary events, the rate of first diagnosed angina increased during the 20 year period, by an average of 2.6% per year. This increase was apparent for uncomplicated angina and angina diagnosed after myocardial infarction, but it was larger for angina diagnosed after myocardial infarction. Because of the opposing trends in major coronary events and angina, the rate of first diagnosed coronary heart disease changed little over the 20 year period. Trend estimates for the last 10 year period of follow-up (1988-90 to 1998-2000) are also given in table 2 for the three main end points. These indicate the same pattern of opposing trends for major coronary events and angina, and no clear change in the rate of first diagnosed coronary heart disease. Of all 1141 first major coronary events, 492 were fatal within 28 days. The average annual decline in case fatality at 28 days of first major coronary events was moderate and non-significant (relative change in risk -1.4, 95% confidence interval -3.1 to 0.4, P = 0.12 over the 20 year period).
Fig 1 Occurrence of coronary events among 7735 men during 20 years of follow-up
Fig 2 Rates of coronary events (per 1000 person years) by calendar period and age group at start of period
Table 2 Age adjusted estimates of annual relative percentage changes in rates of coronary events
The rate of major coronary events fell among men from both manual and non-manual social class groups (annual changes -3.3% for manual and -4.6% for non-manual), and the rate of diagnosed angina increased (annual changes 2.6% and 2.7%, respectively) over the 20 year period. We found no evidence that the magnitude of these trends differed according to social class group (interaction tests: P = 0.31 for major coronary events and P = 0.99 for diagnosed angina).(Fiona C Lampe, lecturer1, Richard W Morr)