Most evidence for an association between excess body weight and cancer risk has been derived from studies of relatively short duration with little reference to the effect on tumor site. This study was designed to evaluate the association between categories of body mass index (BMI: <20, 20-25, 25-30, and >30 kg/m2) and the incidence of colon and lung cancer over 43 years of follow-up (1963-2006), in 10,043 men from the Israeli Ischemic Heart Disease (IIHD) prospective cohort (mean age at baseline 49.3 years, mean BMI 25.7 kg/m2). Data from the Israel National Cancer Registry was linked with the IIHD, and the Cox proportional hazards regression model was applied to analyze the relative risks for lung and colon cancer across BMI categories at baseline. Three hundred cases of lung cancer (2.9%) and 328 cases of colon cancer (3.3%) were diagnosed in the total population. Applying a multivariate model adjusted for age, smoking intensity, and total cholesterol, higher BMI category was associated with an increased risk of colon cancer [HR = 1.22 (95% CI 1.02-1.45)], and with a decreased risk for lung cancer [HR = 0.66 (95% CI 0.56-0.77)]. In this long-term follow-up study over four decades, we observed a consistent dose-response pattern between BMI and increased risk for colon cancer, but decreased risk for lung cancer. Specific associations between excess body weight and cancer risk may suggest different patterns of body fat and cancer incidence at a given site.
Keywords: body mass index; cancer incidence; cohort study; colon cancer; lung cancer.