Environmental factors, medical and family history, and comorbidities associated with primary biliary cholangitis in Japan: a multicenter case–control study

Background Primary biliary cholangitis (PBC) is considered to be caused by the interaction between genetic background and environmental triggers. Previous case–control studies have indicated the associations of environmental factors (tobacco smoking, a history of urinary tract infection, and hair dye) use with PBC. Therefore, we conducted a multicenter case–control study to identify the environmental factors associated with the development of PBC in Japan. Methods From 21 participating centers in Japan, we prospectively enrolled 548 patients with PBC (male/female = 78/470, median age 66), and 548 age- and sex-matched controls. These participants completed a questionnaire comprising 121 items with respect to demographic, anthropometric, socioeconomic features, lifestyle, medical/familial history, and reproductive history in female individuals. The association was determined using conditional multivariate logistic regression analysis. Results The identified factors were vault toilet at home in childhood [odds ratio (OR), 1.63; 95% confidence interval (CI), 1.01–2.62], unpaved roads around the house in childhood (OR, 1.43; 95% CI, 1.07–1.92), ever smoking (OR, 1.70; 95% CI, 1.28–2.25), and hair dye use (OR, 1.57; 95% CI, 1.15–2.14) in the model for lifestyle factors, and a history of any type of autoimmune disease (OR, 8.74; 95% CI, 3.99–19.13), a history of Cesarean section (OR, 0.20; 95% CI, 0.077–0.53), and presence of PBC in first-degree relatives (OR, 21.1; 95% CI, 6.52–68.0) in the model for medical and familial factors. Conclusions These results suggest that poor environmental hygiene in childhood (vault toilets and unpaved roads) and chronic exposure to chemicals (smoking and hair dye use) are likely to be risk factors for the development of PBC in Japan.