Incidence and prevalence of ischaemic heart disease among urban busdrivers in Copenhagen.

A 5-year follow-up study was conducted among all male busdrivers in Copenhagen, Denmark, in addition to the cross-sectional study. In the follow-up study, the SMR for death due to ischaemic heart disease (ICD 410-414) was 144 and SMR for first clinical episode of acute myocardial infarction (ICD 410) was 139, with men in Copenhagen as controls. 80% of the busdrivers (1396 men) participated in the cross-sectional study. The prevalence of questionnaire-positive angina pectoris was 4.9%; in all age groups this was higher than among the controls, locomotive drivers in Denmark. The high health-related selection of busdrivers is assumed to cause an underestimation of the relative occurrence of ischaemic heart disease. Possible explanations for the findings in this study are discussed.