Adult weight gain and colorectal adenomas - a systematic review and meta-analysis.

Background: Colorectal adenomas are known as precursors for the majority of colorectal carcinomas. While weight gain during adulthood has been identified as a risk factor for colorectal cancer, the association is less clear for colorectal adenomas. We conducted a systematic review and meta-analysis to quantify the evidence on this association. Methods: : We searched MEDLINE up to September 2016 to identify observational (prospective, cross-sectional and retrospective) studies on weight gain during adulthood and colorectal adenoma occurrence and recurrence. We conducted meta-analysis on high weight gain versus stable weight, linear and non-linear dose-response meta-analyses to analyze the association. Summary odds ratios (OR) and 95% confidence intervals (95% CI) were estimated using a random effects model. Results: For colorectal adenoma occurrence, the summary OR was 1.39 (95% CI: 1.17-1.65; I 2 :43%, N =9 studies, cases=5,507) comparing high (midpoint: 17.4 kg) versus stable weight gain during adulthood and with each 5 kg weight gain the odds increased by 7% (2%-11%; I 2 :65%, N =7 studies). Although there was indication of non-linearity ( Pnon-linearity