Multivariate analyses of mortality from coronary heart disease due to biological and behavioural factors

Abstract

Due to affluence and a sedentary life style a great deal of people in the western countries are affected by coronary heart disease (CHD). The relation between CHD and certain risk factors pertaining to life style is evaluated in this study. A primary purpose is to study certain crucial risk factors for women. The main variables are age, smoking, overweight (measured by BMI), blood pressure and exercise. This prospective study is based on self-reported data from the nation-wide Swedish Level of Living Survey and on data from the national Cause of Death Register. The data were analysed separately by sex using a proportional hazards model. The sample was divided into two strata: those with heart disease and/or diabetes initially, and all the rest. A sample of 2546 men and 2760 women between 45 and 74 years of age was followed from 1980 to the end of 1990. During this period 189 men and 75 women died of coronary heart disease (CHD). It was found that high blood pressure raised the relative risk (RR) of death from CHD by almost 60% in both men and women. Male smokers (< 14 cigarettes a day) had about 60% (significant) and female smokers (< 10 cigarettes a day) 150% (significant) excessive mortality from CHD. Different levels of overweight among women were strongly related to excess mortality from CHD, ranging between 100 and 300%. Among men there was no such relation. Lack of physical activity showed only a weak (non-significant) increased risk of death due to CHD. Diabetes was also found to be an important risk factor for mortality from CHD, especially among women, being seven times as high as among non diabetics. A test of sex differences revealed that there were two significant interactions, namely between sex and overweight, and between sex and age. Background variables in relation to mortality from all cardiovascular diseases (CVD) were also studied. There were of course many similarities between the effects of the background variables in both the disease groups, but there were interesting differences too, e.g. overweight turned out to be a significant risk factor also for men and physical inactivity for women.