Personal history of gallstones and risk of incident psoriasis and psoriatic arthritis in U.S. women

Background Metabolic syndrome has been associated with both gallstones and psoriasis, suggesting a potential biological linkage between gallstones and psoriasis. However, the association between gallstones and psoriasis has not yet been studied. Objectives To investigate the association between gallstones and psoriasis. Methods This was a prospective cohort study [Nurses' Health Study II (1991-2005)]. Women aged 25-42 years who were free from psoriasis at baseline and who responded to a 2005 follow-up questionnaire regarding their diagnosis of psoriasis were included (n = 89 230). The relative risk (RR) of developing psoriasis or psoriatic arthritis (PsA), which were self-reported and validated by supplemental questionnaires, was measured. Results In this population, 2206 participants had gallstones confirmed by a history of cholecystectomy at baseline. A total of 642 individuals had a diagnosis of incident psoriasis, of whom 157 had concomitant PsA. After adjusting for known risk factors of psoriasis besides body mass index (BMI), a baseline history of cholecystectomy-confirmed gallstones was associated with increased risk of psoriasis [multivariate-adjusted RR 2·20, 95% confidence interval (CI) 1·56-3·10] and concomitant PsA (multivariate-adjusted RR 4·41, 95% CI 2·70-7·18). After additionally adjusting for BMI, the fully adjusted RRs associated with a history of cholecystectomy-confirmed gallstones were 1·70 (95% CI 1·20-2·41) for psoriasis and 2·96 (95% CI 1·80-4·89) for PsA. Conclusions Personal history of gallstones was associated with an increased risk of psoriasis and PsA, independent of obesity, in a cohort of U.S. women. What's already known about this topic? Psoriasis, a debilitating chronic disease, may share some common risk factors, and thus aetiological pathways, with gallstones. To date, the association between gallstones and psoriasis has not been investigated. What does this study add? A history of cholecystectomy-confirmed gallstones was associated with a higher relative risk of developing both psoriasis and psoriatic arthritis (PsA). A history of gallstones was associated with increased risk of developing concomitant PsA, especially in patients with a body mass index < 30 kg m^-2.