Obesity is an initiator of colon adenomas but not a promoter of colorectal cancer in the Black Women’s Health Study

Evidence for the association of anthropometrics with colorectal neoplasms is limited for African Americans. We examined anthropometric measures with both colorectal adenoma and colorectal cancer (CRC) risk in the ongoing Black Women's Health Study. In a nested case–control analysis, 954 cases of colorectal adenoma were compared with 3,816 polyp-free controls, matched on age and follow-up time. For the CRC analyses, 413 incident CRC cases were identified over a 16-year follow-up (802,783 person-years). Adenoma cases and CRC were verified by medical record review. We used multivariable conditional logistic regression analyses (for adenoma) and Cox proportional hazards analyses (for CRC) that included anthropometric exposures and selected confounders. Overall body mass index (BMI) and other anthropometric factors were not associated with colorectal adenoma or cancer risk in Black women. However, increased risk of adenoma (but not CRC) was observed among especially related to adenomas in the proximal colon. Among women ≥ 50 years of age, risk of proximal adenoma increased 14% (95% CI 1.00, 1.31), 35% (95% CI 1.12, 1.63), and 25% (0.93, 1.68) with each standard deviation increase in BMI, waist circumference, and waist-to-hip ratio, respectively. None of the anthropometric factors were associated with young onset CRC or adenoma risk. Our results suggest that obesity might be an initiator for colon adenomas but not a promoter for colorectal cancer among Black women.