Prevalence of coronary heart disease in icelandic men 1968-1986: The reykjavik study

The prevalence of coronary heart disease (CHD) was determined in a general population sample of 9141 Icelandic men aged 34-79 years, and the prevalence of four different forms of CHD was estimated separately: symptomatic infarction fulfilling WHO-MONICA criteria for definite myocardial infarction; myocardial infarction detected by ECG changes only (unrecognized, silent infarction); angina pectoris detected by the Rose questionnaire and associated with ECG manifestations of myocardial ischaemia, either at rest or during exercise, but no manifestations of myocardial infarction; angina pectoris without ECG changes indicative of myocardial ischaemia. The study was conducted in five stages allowing evaluation of trends from 1968-1986. Age was a major determinant of the prevalence of all forms of CHD. Thus, the prevalence of myocardial infarction (symptomatic or silent) rose from undetectable levels in the youngest age group (30-34 years) to around 12% (7% symptomatic and 5% silent) in the oldest group (75-79 years) and the prevalence of all forms of CHD rose from 4% in the youngest age group to 23% in the age group 70-74 years. Age-standardized comparison was carried out on the prevalence of the different forms of CHD at different stages of the study in 50-64-year-old men who were represented in all stages of the study. There was a gradual increase in the prevalence of myocardial infarction from 3% (symptomatic and silent combined, CI 1.9-4-8) in 1968 to 4.9% in 1986 (CI 3.9-6.1) (P<0.001). Conversely there was a statistically significant fall in the prevalence of angina pectoris, with or without ECG-manifestations of myocardial ischaemia, from 11.3% (CI 8.8-14.4) in 1968 to 5% in 1986 (CI 4.0-6.2) (P<0.001). This decrease was of sufficient magnitude to more than offset the rise in infarct prevalence, resulting in a significant fall in the prevalence of all CHD from 14.3% (CI 11.5-17.8) in 1968 to9.9% (CI 8.5-11.5) in 1986 in 50-64-year-old men. This trend is in general agreement with the previously reported decline in age-standardized mortality from CHD and the incidence of myocardial infarction in Iceland.