Adiposity and risks of colorectal and small intestine cancer in Chinese adults: a prospective study of 0.5 million people

BACKGROUND: Uncertainty remains about the associations of adiposity with intestinal cancer in China and by its anatomical subtype. METHODS: The prospective China Kadoorie Biobank recorded 3024 incident cases of colorectal (CRC) and 143 cases of small intestine (SIC) cancer during a 10-year follow-up among 509 568 participants without prior cancer at baseline. Cox regression was used to estimate adjusted hazard ratios (HRs) for specific cancers associated with adiposity. RESULTS: Overall mean body mass index (BMI) was 23.7 kg/m(2). BMI was positively associated with CRC (HR per SD 1.10 [95% CI 1.06–1.14]), colon (1.13 [1.07–1.18]), and rectal (1.07 [1.02–1.13]) cancer. For waist circumference, the corresponding HRs per SD were 1.14 (1.10–1.18), 1.18 (1.13–1.24), and 1.11 (1.05–1.16), respectively. The adjusted HRs were somewhat greater in men than women. Adiposity was positively, but non-significantly, associated with SIC risk. CONCLUSIONS: Among relatively lean Chinese adults, adiposity was associated with risks of colon and rectal cancer, with the associations somewhat stronger in men than women.