Coeliac disease risk doubles in patients with alopecia areata: a nationwide case-control study.

Alopecia areata (AA) and coeliac disease (CD) are both common immune-mediated diseases. Despite increasing evidence of bidirectional associations between the two diseases, the data remain unclear and inconsistent. Here, we explored the association between AA and CD in a large representative population cohort. Patients diagnosed with AA between 2005 and 2019 were compared with age-matched and gender-matched healthy controls for coeliac autoimmunity. In total, 33 401 patients with AA and 66 802 controls were included in the analysis. Overall, 754 patients (0.75%) had CD. Compared with controls, CD prevalence was twofold higher among patients with AA (1.1% vs. 0.6%, odds ratio 1.95, 95% confidence interval 1.69-2.25). A higher prevalence of CD was observed in patients with AA among all age groups, with the highest risk in patients with AA who were aged 40 years or more. AA may be associated with a significantly increased risk of CD, suggesting the need for early diagnostic and preventive measures.