Case-control studies of risk factors for primary biliary cirrhosis in two United Kingdom populations

Objective The aetiology of primary biliary cirrhosis (PBC) is largely unknown. Previous studies have indicated that both environmental and genetic risk factors may be important. Design We undertook a large case-control study to study possible risk factors in more detail. All patients were sent postal questionnaires on risk factors. Patients We identified two sets of PBC cases from a geographically defined epidemiology study (epidemiological cases) and from a survey of the national patient support group (Foundation cases). Controls were selected from the electoral roll in strata matched to epidemiological cases by quartiles of age and sex. Results Analysable questionnaires were received from 318 epidemiological cases, 2258 Foundation cases and 2438 controls. Statistically significant associations were seen with smoking (OR=1.63 (95% CI, 1.27 to 2.09)), epidemiological cases versus controls (1.57 (1.39 to 1.78)), Foundation cases versus controls, hair dye use (1.37 (0.98 to 1.80)), 1.25 (1.07 to 1.46)), and with previous histories of psoriasis (1.90 (1.21 to 1.91), 2.33 (1.03 to 1.73)), urinary infections (2.06 (1.56 to 0.1.73), 1.80 (1.54 to 2.11)), and shingles (2.38 (1.82 to 3.11), 1.23 (1.08 to 1.43)) and previous autoimmune diseases. Alcohol consumption was negatively associated with PBC (0.57 (0.39 to 0.83), 0.73 (0.61 to 0.79)). We did not identify any associations with obstetric risk factors except a previous history of obstetric cholestasis (2.13 (1.25 to 3.59), 2.20 (1.61 to 3.03)). Conclusion We have confirmed that among environmental risk factors, smoking and the use of some cosmetics as well as urinary infections appear important. Among possible genetic risk factors a family history of PBC is a strong association and that a previous history of obstetric cholestasis as another putative 'genetic' risk.