Body mass index and the risk of male cancer mortality of various sites: 17-year follow-up of the Basel cohort study.

Questions Under Study: There is growing evidence for a link between body weight and cancer risk, but there is not a clear consensus yet.

Methods: We studied the association between body mass index (BMI) and overall, lung, prostate and colon cancer mortality. In 1971/73, weight and height were measured in 2974 men working in Basel, Switzerland. In 1990, the vital status of all participants was assessed.

Results: 290 men had died from cancer, 87 from lung, 30 from prostate, and 22 from colon cancer. In the predefined Cox Proportional Hazards Regression Models for survival analysis, a baseline hazard was modified multiplicatively by covariates, i.e. the untransformed continuous variable "BMI" was chosen as covariate. In addition it was assumed that the baseline hazard may be different for smokers, non-smokers and different age groups (age at entry into study). Thus, multiple strata, i.e. combinations of smoking status and age groups were allowed. With increasing BMI overall cancer mortality did not change. Accordingly, the relative risk (RR) per 1-unit increase of BMI (unit = 1 kg/m2) was 1.03 (95% CI: 0.99-1.07). In relation to lung cancer, mortality did neither increase nor decrease with increasing BMI (RR = 1.0; 95% CI 0.93- 1.07). The results for prostate cancer mortality were similar, i.e. no correlation with BMI was observed (RR = 0.95; 95% CI: 0.93-1.18). The same was true for colon cancer mortality (RR = 1.09; 95% CI: 0.92-1.24).

Conclusions: This investigation provides little evidence of an association between BMI and mortality of all cancers combined, cancer of the lung, the prostate and the colon.