Are regional variations in ischaemic heart disease related to differences in coronary risk factors? The project 'myocardial infarction in mid-Sweden'.

In a previous report, a large regional variation was reported in total mortality and mortality rate from ischaemic heart disease (IHD) in mid-Sweden. In this report, IHD prevalence and risk factor data are presented. A postal questionnaire was sent out to a random sample of men aged 45-64 years in each of 40 communities. 14,675 men (88%) responded. Based on a validity study, IHD cases were defined as those with a history of myocardial infarction and/or angina pectoris. Age, smoking habits, antihypertensive treatment, body mass index, food habits, stress and physical activity during leisure time were used as risk factors. IHD prevalence showed the same geographical variation as IHD mortality, with a low prevalence in the east and a high prevalence in the west. There was a moderate variation in risk factor levels over the 40 communities. When this variation was taken into account the geographical IHD variation was somewhat smaller but still substantial. Other factors may involve socio-economics, drinking water qualities, mineral soil content or other environmental factors. Which of these cause the largest IHD variation is at present unknown, but is subject to systematic examination in this project.