Association between the first exposure to general anesthesia and alopecia areata

Alopecia areata (AA) is an autoimmune cutaneous disorder reported to be related to various immunologic diseases and psychiatric disorders. Some AA patients report the onset of patchy hair loss after surgeries under general anesthesia (GA). However, no large-scale studies have been conducted on the relationship between AA and GA. Thus, we aimed to evaluate whether exposure to GA is associated with an increased risk of AA. In this retrospective study, we analyzed a population exposed to GA. These individuals were compared to unexposed controls, matched by age, sex, income level, and comorbidities (propensity score matching, 1:2 ratio), from the national sample cohort from January 1, 2002, to December 31, 2015. Hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated for the risk of AA associated with GA using Cox proportional hazard regression. As a result, the risk of AA occurrence was significantly higher in the GA-exposed group after adjusting confounding factors (adjusted HR 1.22, 95% CI 1.07–1.43, P = 0.005). The cumulative incidence of AA was higher in the GA-exposed group (log-rank P = 0.005). The risk of AA increased with GA exposure time. However, the type of surgery and the method of anesthesia did not impact the risk of developing AA. Thus, in conclusion, exposure to GA was associated with a higher risk of developing AA.