Background: Previous studies have suggested that diabetes mellitus (DM) is a risk factor for gallbladder cancer; however, it remains unclear whether DM with or without gallstones increases the risk of gallbladder cancer. The aim of this study was to evaluate the risk factors for gallbladder cancer, including sex, hypertension, hyperlipidemia, gallstones, and DM.
Methods: The study cohort consisted of 214,179 subjects newly diagnosed with diabetes (cases) collected from the claims data of the Health Insurance Program of Taiwan from 2000 to 2001 who were retrospectively enrolled. The control group consisted of 206,860 subjects without diabetes, matched with the cases for sex, age, and index year. The subjects were followed up until the end of 2008. The effects of the risk factors on the incidence of gallbladder cancer were evaluated with Cox's proportional hazard regression models.
Results: The risk of gallbladder cancer was higher in the DM group than in the non-DM group, with a hazard ratio (HR) of 1.53 [95 % confidence interval (CI) 1.22-1.90]. Gallstones were also a risk factor for gallbladder cancer, with an HR of 2.52 (95 % CI 1.11-5.73). DM and gallstones were synergistic risk factors for gallbladder cancer (p < 0.0001), with an HR of 5.37 (95 % CI 3.17-9.10) for subjects with both diseases in relation to those with neither of these conditions.
Conclusions: In the present long-term cohort study, DM with or without gallstones increased the risk of gallbladder cancer. Gallstones were independently related to gallbladder cancer, and DM and gallstones were synergistic risk factors for gallbladder cancer.