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Background It is not known whether alopecia areata (AA) is associated with a greater or reduced risk for infection. Aim We undertook a population-based study exploring associations between AA and common infections. Methods We extracted primary care records from the UK Oxford-Royal College of General Practitioners Research and Surveillance Centre database (trial registration: NCT04239521). The incidence of common and viral infection composite outcomes, and individual respiratory, gastrointestinal (GI), skin, urinary tract, genital and herpes infections, were compared in people with AA (AA group, n = 10 391) and a propensity-matched control group (n = 41 564). Adjusted hazard ratios (aHRs), controlling for sociodemographic and clinical covariates, and comorbidities were used to estimate the association between AA and each infection over 5 years. Results The incidence (per 100 person-years) of common infections was slightly higher in the AA group [14.2, 95% confidence interval (CI) 13.8–14.6] than the control group (11.7, 95% CI 11.5–11.9). In adjusted analysis, positive associations were observed for composite outcomes (common infections aHR 1.13, 95% CI 1.09–1.17; viral infections aHR 1.11, 95% CI 1.07–1.16) and with respiratory tract, GI, skin and herpes simplex infections (aHR range 1.09–1.32). Excluding people in the control group without a recent consultation with their general practitioner showed no association between AA and infection (common infections aHR 1.01, 95% CI 0.98–1.05, viral infections aHR 0.99, 95% CI 0.95–1.03). Conclusions The association between AA and common infection may represent a higher propensity of people with AA to engage with healthcare services (and thereby to have infections recorded), rather than a true association between AA and infection. Overall our findings suggest that AA is not associated with a clinically significantly increased or decreased incidence of common infections. [ABSTRACT FROM AUTHOR]

Background Alopecia areata (AA) has features of both autoimmune and atopic pathogenesis, but information on the risk of people with AA developing autoimmune and atopic conditions is limited. Objective To assess the prevalence and incidence of atopic and autoimmune conditions in people with AA. Methods This was a population-based cohort study of 8051 adults with newly diagnosed AA (AA group) and 32 204 adults in the matched control group, using the UK Oxford-Royal College of General Practitioners (RCGP) Research and Surveillance Centre (RSC) network primary care database, 2009–2018 (trial registration number: NCT04239521). Baseline prevalence of common atopic and autoimmune conditions, and risk of new-onset atopic and autoimmune disease, were estimated. Results Atopic and autoimmune conditions were more prevalent in the AA group than the control group (atopic 37.2% vs. 26.7%, autoimmune 11.5% vs. 7.9%). The AA group were 43% more likely to develop any new-onset atopic condition [adjusted hazard ratio (aHR) 1.43. 95% confidence interval (CI) 1.28–1.61] and 45% more likely to develop any autoimmune condition (aHR 1.45, 95% CI 1.28–1.66) compared with the control group. When examining individual conditions, the AA group were at increased risk of atopic dermatitis (aHR 1.91, 95% CI 1.67–2.19), allergic rhinitis (aHR 1.32, 95% CI 1.14–1.54), autoimmune hypothyroidism (aHR 1.65, 95% CI 1.35–2.02), systemic lupus erythematosus (aHR 4.51, 95% CI 1.88–10.82) and vitiligo (aHR 2.39, 95% CI 1.49–3.82). There was no evidence for a higher incidence of other conditions examined. Conclusion People with AA have an increased burden of atopic and autoimmune comorbidity. This supports previous work suggesting that both T helper cell (Th)1 and Th2 immune responses may be implicated in the pathogenesis of AA. [ABSTRACT FROM AUTHOR]