<show/>Epidemiology of alopecia areata and population-wide comorbidities in Germany: analysis of longitudinal claims data

Background Alopecia areata (AA) is a chronic, immune-mediated disease characterized by acute-onset hair loss. The hair loss can range from small, circumscribed hairless areas on the scalp to complete loss of hair on the head and body hair. However, data on the epidemiology of AA are limited. Current evaluations are lacking in Germany. The aim of this study was to evaluate the epidemiology and comorbidity of AA in Germany based on claims data.Methods A representative 40% sample of all adults who were insured with a German statutory health insurance company (DAK-Gesundheit) between 2016 and 2020 was evaluated (n = 2.88 million). Based on at least one relevant outpatient or inpatient diagnosis of International Classification of Diseases (ICD)-10 L63, the annual AA prevalence and incidence (ICD-10 L63) were calculated for 2016 to 2020. Different case definitions were used for diagnosis validation. In addition, the occurrence of comorbidities in patients with AA was investigated.Results In 2020, AA prevalence was 210 cases per 100 000 and incidence 72 cases per 100 000. Compared with persons without AA, those with AA significantly more often had atopic dermatitis [rate ratio (RR) 2.9], pruritus (RR 2.7), lupus erythematosus (RR 2.4), urticaria (RR 2.3) and psoriasis (RR 2.2). Women were affected slightly more often than men (0.2% vs. 0.1%). On a regional level, higher prevalence and incidence rates were found in Brandenburg (prevalence 332 cases per 100 000; incidence 116 cases per 100 000), Hesse (prevalence 344 cases per 100 000; incidence 124 cases per 100 000) and Mecklenburg-Western Pomerania (prevalence 303 cases per 100 000; incidence 111 per 100 000).Conclusions AA is a common immune-mediated skin condition with marked regional variations in Germany. For a complete understanding of epidemiology, complementary population-based studies including clinical characteristics of AA are useful.