Objective: To assess to what extent the incidence of coronary events and death related to smoking, hypertension, hyperlipidemia and diabetes is modified by obesity.
Design: Prospective cohort study.
Subjects: A total of 22 025 men aged 27 to 61-y-old at entry.
Measurements: Incidence of coronary events (CE, ie acute myocardial infarctions and deaths due to chronic ischaemic heart disease) and death during 23 y of follow-up was studied in relation to body mass index (BMI), heart rate, blood pressure, blood lipids, glucose and insulin, lifestyle factors, history of angina pectoris, history of cancer, self-reported health and socio-economic conditions.
Results: At the end of follow-up 20% of the obese men were no longer alive, and 13% had had a coronary event. Incidence of CE was 16% lower (RR (relative risk) 0.84; 95% confidence interval (CI) 0.65-1.10) among underweight (n=1171), 24% higher (RR 1.24; CI 1.12-1.37) among overweight (n=7773), and 76% higher (RR 1.76; 95% CI 1.49-2.08) among obese men (n=1343) than it was among men with normal BMI (n=11 738). The risk associated with overweight and obesity remained statistically significant after adjustment for potential confounders (RR 1.18; CI 1.07-1.31; and 1.39; 1.17-1.65, respectively). The association between BMI and mortality was J-shaped. In all, 1.7% of the obese men were smokers with hypertension, hyperlipidaemia and diabetes, 16.3% were not exposed to any of these risk factors. The cardiovascular risk associated with obesity was small in the absence of other risk factors. Between smoking and obesity there was a statistically significant synergistic effect.
Conclusions: Obesity is associated with an increased incidence of coronary events and death. The risk associated with obesity is substantially increased by exposure to other atherosclerotic risk factors, of which smoking seems to be the most important. The preventive potential of these associations should be evaluated in controlled trials.