Obesity is a known cause of gallstone formation and gallstones increases the risk of gallbladder cancer (GBC), but the relation of body mass index (BMI) to GBC remains incompletely understood. To help elucidate the role of obesity in GBC, we performed a meta-analysis of the relationship between BMI and GBC risk. PUBMED and EMBASE databases were searched up to April 17, 2016. Fifteen articles with 5902 cases were identified. Random-effects models and dose-response meta-analyses were used to pool study results. Compared to normal weight, the pooled relative risks (RRs) and the corresponding 95% confidence intervals (CI) of GBC for overweight and obesity is 1.10 (0.98-1.23) and 1.58 (1.43-1.75) respectively. The RRs and 95% CI of overweight and obesity in man are 0.98 (0.90-1.08) and 1.43 (1.19-1.71), while the corresponding RRs in woman are 1.29 (1.08-1.55) and 1.68 (1.41-2.00) when compared to normal weight. A nonlinear dose-response relationship between BMI and risk of GBC was found (P=0.001), and the risk increased by 4% for each 1 kg/m2 increment in BMI. When adjusted for sex, at the point of BMI=25 kg/m2, the RRs (95% CIs) for women and men were 1.13 (1.01-1.25) and 0.98 (0.90-1.07) respectively. The corresponding RRs (95%CIs) at the point of BMI=30 kg/m2 were 1.56(1.39-1.75) vs. 1.24(1.06-1.44). These results suggest that association of obesity and risk of GBC is stronger in woman. Furthermore, overweight is only associated with GBC in woman. A even stricter weight control might be necessary for woman to prevent GBC.
Keywords: BMI; gallbladder cancer; meta-analysis; obese; overweight.