BODY-MASS INDEX AND CARDIOVASCULAR MORTALITY AT DIFFERENT LEVELS OF BLOOD-PRESSURE - A PROSPECTIVE-STUDY OF NORWEGIAN MEN AND WOMEN

Study objective - The study investigated the joint effect of body mass index and systolic blood pressure on cardiovascular and total mortali ty. Design - This was a prospective cohort study. The main outcome mea sures were age adjusted mortality and relative risks estimated from su rvival models. Setting - The population of the city of Bergen, Norway. Participants - Subjects were 21 145 men and 30 330 women aged 30-79 y ears at the time of examination in 1963. Main results - Both cause spe cific and all cause mortality increased with systolic blood pressure w ithin each category of body mass index. Stroke mortality was not signi ficantly associated with body mass index when adjusted for systolic bl ood pressure in either age group of men or women. Coronary heart disea se mortality increased on average 30% per 5 kg/m(2) increase in body m ass index in men and women aged 30-59 years at baseline. Adjusted for systolic blood pressure, the relative risks were reduced to 1.20 (95% confidence interval (CI) 1.12, 1.29) in men and 1.10 (95% CI 1.03, 1.1 8) in women. They were similar at each level of systolic blood pressur e. For coronary heart disease mortality in men and women aged 60-79 ye ars at measurement a negative interaction between body mass index and systolic blood pressure was suggested in the first five years. Excludi ng the first five years, adjusted relative risks per 5 kg/m(2), were 1 .05 (95% CI 0.96, 1.15) in men and 1.11 (95% CI 1.04, 1.17) in women i n the older age group. There was an upturn in cardiovascular mortality at low levels of body mass index in both age groups of women, but not in men. Conclusions - Hypertension is an important risk factor for ca rdiovascular and all cause mortality even in the obese. Body mass inde x is generally a weak predictor of cardiovascular mortality in this po pulation. It is a stronger risk factor of coronary death in men when m easured at a younger age. Thin people with hypertension are not at par ticularly high risk of death from coronary heart disease compared with their obese counterparts, except possibly in the first few years afte r measurement in the elderly. Being underweight is associated with inc reased risk of death from all cardiovascular causes in women, but not in men.