Does obesity modify the effect of blood pressure on the risk of cardiovascular disease? A population-based cohort study of more than one million Swedish men.

BACKGROUND: Some studies have suggested that increased blood pressure has a stronger effect on the risk of cardiovascular disease (CVD) in lean persons than in obese persons, although this is not a universal finding. Given the inconsistency of this result, we tested it using a large population-based cohort data set. METHODS AND
RESULTS: Systolic and diastolic blood pressures (BPs) and body mass index were measured in 1 145 758 Swedish men born between 1951 and 1976 who were in young adulthood (median age 18.2 years). During the register-based follow-up, which lasted until the end of 2006, 65 611 new CVD events took place, including 6799 myocardial infarctions and 8827 strokes. Hazard ratios (HRs) per 1-SD increase in systolic and diastolic BP were computed within established body mass index categories (underweight, normal, overweight, or obese) with Cox proportional hazards models. The strongest associations of diastolic BP with CVD (HR 1.18), myocardial infarction (HR 1.22), and stroke (HR 1.13) were observed in the obese category. For systolic BP, the strongest associations were observed in the obese category with CVD (HR 1.16) and stroke (HR 1.29) but in the overweight category with myocardial infarction (HR 1.19). We observed statistically significant interactions (P<0.0001) with body mass index for diastolic BP in relation to CVD and for systolic BP in relation to CVD and stroke.
CONCLUSIONS: In contrast to the findings of previous studies, we observed a general increase in the magnitude of the association between blood pressure and subsequent CVD with increasing body mass index. Hypertension should not be regarded as a less serious risk factor in obese than in lean or normal-weight persons.