Predictiveness of body mass index for fatal coronary heart disease in men according to length of follow-up: a 21-year prospective cohort study.

Aims: To test the association between body mass index (BMI) and other coronary risk factors and the risk of a fatal coronary heart disease (CHD) event in different time periods during follow-up.

Methods: Prospective cohort study with a 21 year follow-up period. A screened sample of 14,403 men aged 40-49 years initially free of CHD. Risk of fatal CHD was calculated for 21 years' cumulative follow-up and for four consecutive 5-year periods.

Results: After adjustment for age and the other risk factors, total cholesterol and systolic blood pressure retained their predictive strength for CHD mortality throughout follow-up. Though cigarette smoking remained a significant predictor, the relative risk decreased with time (test of trend: p=0.01). Intermediate to vigorous physical activity at leisure was protective for 10 years of follow-up and a question on mental stress for 5 years. The test of trend indicated that the risk associated with BMI increased with the duration of follow-up (p=0.002).

Conclusions: Our data show that coronary risk factors predicted CHD mortality differently according to the length of follow-up, and suggest that the harm associated with obesity may take more than a decade to become evident, in contrast to the classical CHD risk factors.