Do changes in cardiovascular risk factors explain the increasing socioeconomic diVerence in mortality from ischaemic heart disease in Finland?

Study objective—To estimate the extent to which changes in blood pressure, smoking, and serum cholesterol concentration explain the observed increase in socioeconomic diVerences in mortality from ischaemic heart disease (IHD) in Finland during the past 20 years. Design—Predicted changes in mortality from IHD were calculated using logistic regression models with the risk factor levels assessed by cross sectional population surveys conducted in 1972, 1977, 1982, and 1987. The subjects included white collar and blue collar workers and farmers. The predicted changes were compared with the observed mortality changes in the same socioeconomic groups in the total population of the same geographical area. Setting—North Karelia and Kuopio provinces, eastern Finland. Participants—16 741 men and 16 389 women aged 30–59 randomly drawn from the population registers of the study areas. Mortality data were obtained from the total population in the same areas. Main results—In men, the changes in diastolic blood pressure, total serum cholesterol, and smoking predicted a 28% decline in the mortality from IHD among white collar workers, a 30% decline among blue collar workers, and a 33% decline in farmers. Observed declines in the same socioeconomic groups were 61%, 40%, and 37%, respectively. In women, the predicted decline was 41% among white collar workers, 35% among blue collar workers, and 39% among farmers. The respective observed declines were 57%, 43%, and 20%. Conclusions—Less than half of the decline in IHD mortality among white collar men was explained by the risk factor changes, while they explained 75% of the decline among blue collar men and 89% of the decline among male farmers. Changes in risk factors did not explain the increasing diVerence in IHD mortality between the socioeconomic groups, especially among men. (J Epidemiol Community Health 1998;52:416–419) Mortality from ischaemic heart disease (IHD) has been declining in most industrialised countries during the past 20 to 30 years. We have previously reported that most of the decline in IHD mortality in Finland can be explained by a decline in the classic cardiovascular risk factors, smoking, high serum cholesterol, and high blood pressure. Despite this positive development the relative diVerences in IHD mortality between socioeconomic groups have been growing in Finland. 4 Several studies suggest that about half of the diVerences between socioeconomic groups can be explained by the main risk factors. We are not aware of any previous studies, however, that relate changes in socioeconomic diVerences in IHD mortality with changes in risk factor levels in a population. The aim of this paper is to assess the extent to which the changes in blood pressure, smoking, and serum total cholesterol can explain the observed growing socioeconomic diVerences in IHD mortality in Finland. Methods Four cross sectional population surveys, conducted in 1972, 1977, 1982, and 1987, have assessed the levels of coronary risk factors in Finland’s eastern provinces of North Karelia and Kuopio. For each survey, an independent random sample was drawn from the national population register. In the 1972 and 1977 surveys, a random sample of 6.6% of the population born during 1913–1947 was drawn in both areas. In 1982 and 1987, each area’s samples were stratified by sex and 10 year age group. The age range in all four surveys was 30–59 years. The survey methods used in 1982 and 1987 followed the WHO MONICA (Multinational MONItoring of trends and determinants in CArdiovascular disease) protocol, which were comparable with the methods used in 1972 and 1977. Blood pressure was measured from the right arm of the subject, who was seated for five minutes before the measurement. The fifth phase of the KorotkoV sounds was recorded as the diastolic pressure. In 1972 and 1977, a shorter cuV bladder (23 cm) was used than in 1982 and 1987 (42 cm). Table 1 Samples (number) and participation rates (%) by sex, year, and area in persons aged 30–59 years Year North Karelia Kuopio Province