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/m2 . 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.