Obesity and the risk of cholangiocarcinoma: a meta-analysis

A number of studies have shown that obesity is implicated in the susceptibility to several cancers. However, the association between obesity and cholangiocarcinoma remains unclear. This meta-analysis aimed to quantitatively assess the association between overweight or obesity and the incidence of cholangiocarcinoma. A literature search was performed for cohort and case-control studies published from 1996 to 2013 using PubMed, Cochrane, and EMBASE databases. Studies were included if they reported odds ratios (ORs) and corresponding 95 % confidence intervals (CIs) of cholangiocarcinoma with respect to obesity or overweight. Normal weight, overweight, and obesity were defined when the body mass index (BMI) was 18.5–24.9, 25–29.9, and ≥30 kg/m², respectively. Excess body weight was defined as BMI ≥ 25 kg/m². Ten studies met the inclusion criteria, which included five cohort and five case-control studies. Compared with normal weight, being overweight (pooled OR 1.30, 95 % CI 1.13–1.49), obesity (pooled OR 1.52, 95 % CI 1.13–1.89), and excess body weight (pooled OR 1.37, 95 %CI 1.22–1.55) were significantly associated with cholangiocarcinoma. The funnel plot revealed no evidence for publication bias. Obesity is associated with the increased risk of cholangiocarcinoma, which needs to be confirmed by long-term cohort studies.