Body mass index, body height, and subsequent risk of colorectal cancer in middle-aged and elderly Japanese men and women: Japan Public Health Center-based Prospective Study

Objective: To investigate the association of body mass index (BMI) or body height with colorectal cancer incidence in a population-based prospective study. Methods: We identified 986 (626 men and 360 women) newly diagnosed cases of colorectal cancer during the 9.4-year follow-up of a cohort consisting of 102,949 (49,158 male and 53,791 female) middle-aged and elderly Japanese. Results: Lower BMI groups (lower than 23) were not associated with colorectal cancer compared with the 23-24.9 BMI group. Any categories of 25-26.9, 27-29.9, or 30 or more BMI were associated with an increased risk of colorectal cancer compared with the lower than 25 BMI (RR, 1.2 for 25-26.9, 1.4 for 27-29.9, and 1.5 for 30 or more; p for trend, 0.004) in men. These associations were more evident only in invasive-type cancer analysis. BMI was not associated with the risk of colorectal cancer in women. No significant association with height was obtained for either men or women. Conclusions: The association of BMI with colorectal cancer was confirmed in a Japanese population as well as Western populations. Only invasive-cancer analysis suggested that BMI was important for tumor growth and proliferation. Approximately 6.7% of colorectal cancer was attributable to a BMI of 25 or higher in middle-aged and elderly Japanese men.