Body Mass Index and Risk of Gallbladder Cancer: Systematic Review and Meta-Analysis of Observational Studies

OBJECTIVES: To provide a quantitative assessment of the association between excess body weight, interpreted as increased body mass index (BMI), and the risk of gallbladder cancer (GBC). METHODS: We identified eligible studies in Medline and EMBASE up to 1 February 2015, and reference lists of retrieved articles. Summary relative risks with their 95% confidence intervals were calculated in a random-effects model. Subgroup analyses were performed according to study design, gender, geographic location, ascertainment of exposure and adjustment for confounders. RESUITS: A total of 12 cohort studies and 8 case-control studies were included in the meta-analysis. Overall, compared with “normal” weight, the summary relative risks of GBC were 1.14 (95% CI, 1.04–1.25) for overweight individuals (BMI 25–30 kg/m(2)) and 1.56 (95% CI, 1.41–1.73) for obese individuals (BMI > 30 kg/m(2)). Obese women had a higher risk of GBC than men did (women: SRRs 1.67, 95% CI 1.38–2.02; men: SRRs 1.42, 95% CI 1.21–1.66), and there was significant association between overweight and GBC risk in women (SRRs 1.26, 95% CI 1.13–1.40), but not in men (SRRs 1.06, 95% CI 0.94–1.20). CONCLUSIONS: Findings from this meta-analysis indicate that obesity is associated with an increased risk of GBC, especially in women. Overweight is associated with GBC risk only in women.