Body weight, fat distribution and colorectal cancer risk: a report from cohort studies of 134255 Chinese men and women.

OBJECTIVE: The objective was to evaluate the association of body size and fat distribution with the risk of colorectal cancer (CRC) in Chinese men and women.

DESIGN: This was a population-based, prospective cohort study.

SUBJECTS: The analysis included 134,255 Chinese adults enrolled in the Shanghai Women's Health Study and the Shanghai Men's Health Study, with an average follow-up of 11.0 and 5.5 years, respectively.

MEASUREMENTS: Waist circumference (WC), body mass index (BMI) and waist-to-hip ratio (WHR) were measured by trained interviewers at baseline. Multivariable Cox models were used to calculate adjusted hazard ratios (HRs) for incident CRC.

RESULTS: A total of 935 incident CRC cases were identified. Both measures of general adiposity (measured by BMI) and central adiposity (measured by WHR and WC) were significantly associated with an increased risk of colon cancer in men but not in women. Multivariable-adjusted HRs for colon cancer in men in the highest compared with the lowest quintiles were 2.15 (95% confidence interval (CI): 1.35-3.43; P for trend=0.0006) for BMI, 1.97 (95% CI: 1.19-3.24; P for trend=0.0004) for WHR and 2.00 (95% CI: 1.21-3.29; P for trend=0.0002) for WC. The BMI-associated risk was attenuated in analyses stratified by WHR, whereas the WHR-associated risk remained significant in the high BMI stratum (HR for comparison of extreme tertiles of WHR: 3.38, 95% CI: 1.47-7.75; P for trend =0.0002). None of these anthropometric measures were significantly associated with rectal cancer.

CONCLUSION: Obesity, particularly central obesity, was associated with an increased risk of colon cancer in men.