Bidirectional Associations Between Seborrheic Dermatitis and Epithelial Barrier Diseases: A Retrospective Cohort Study.

Abstract

Seborrheic dermatitis (SD) is a common skin disease characterized by epithelial barrier breakdown. The epithelial barrier theory (EBT) implicates epithelial barrier disruption in the development of epithelial barrier diseases (EBDs). We hypothesized that SD is associated with an increased risk of EBDs and investigated the bidirectional association between SD and EBDs. Retrospective cohort study of 5,083,689 patients using a large US administrative claims database from January 1, 2016, to June 30, 2022. The mean (standard deviation) follow-up was 3.25 (1.75) years with a total follow-up of over 16 million person-years. The outcomes were a diagnosis of (i) SD after an EBD and (ii) EBD after SD, analyzed using a multivariable Cox proportional hazards model (hazard ratio [95% confidence interval]). The risk of SD was increased after EBD diagnosis for multiple diseases, including atopic dermatitis [2.46 (2.40, 2.53)], alopecia areata [3.47 (3.24, 3.71)], contact dermatitis [1.92 (1.88, 1.96)], psoriasis [2.62 (2.54, 2.69)], rosacea [2.84 (2.78, 2.90)], hidradenitis suppurativa [1.79 (1.63, 1.97)], rhinosinusitis [1.34 (1.32, 1.35)], food allergy [1.47 (1.42, 1.54)], celiac disease [1.55 (1.43, 1.68)], ocular allergy [1.55 (1.49, 1.61)], and dry eye [1.54 (1.52, 1.56)]. The risk of EBD after SD diagnosis followed similar trends, with the largest effect estimates being psoriasis [3.52 (3.42, 3.61)], rosacea [2.85 (2.79, 2.92)], and alopecia areata [2.81 (2.61, 3.03)]. Our results support the EBT as a shared driver of EBD pathogenesis at not only local (e.g., skin) barriers but also at non-local sites, including the respiratory, gastrointestinal, and ocular epithelial barriers.