Infection with COVID-19 conferred a nearly twofold risk of developing alopecia areata (AA), results from a large analysis of Korean patients demonstrated.
"There is a growing number of reports on new onset, exacerbation, and recurrence of AA after COVID-19," corresponding author Jin Park, MD, PhD, of the Department of dermatology at Jeonbuk National University Medical School, South Korea, and colleagues wrote in a research letter published online on January 10, 2024, in JAMA Dermatology. "However, evidence supporting an association between COVID-19 and AA is limited."
To investigate the association between COVID-19 and AA, the researchers used data from the Korea Disease Control and Prevention Agency–COVID-19–National Health Insurance Service cohort to conduct a propensity score–matched, nationwide, population-based cohort study from October 8, 2020, to September 30, 2021. They used Cox proportional hazards regression to calculate the incidence, prevalence, and adjusted hazard ratios (AHRs) for AA.
The cohort consisted of 259,369 patients with COVID-19 and 259,369 uninfected controls. The researchers observed an increased risk of telogen effluvium in patients with COVID-19 compared with the uninfected controls (AHR, 6.40; 95% CI, 4.92-8.33), while the incidence of epidermal cysts, benign skin tumors, and other negative control outcomes did not differ between groups.
Meanwhile, the incidence of AA in patients with COVID-19 was significantly higher compared with the uninfected controls (43.19 per 10,000 person-years [PY]), regardless of clinical subtype. This translated into an AHR of 1.82 (95% CI, 1.60-2.07). In other findings, the incidence of patchy AA and alopecia totalis and alopecia universalis (AT/AU) was 35.94 and 7.24 per 10,000 PY in patients with COVID-19 compared with 19.43 and 4.18 per 10,000 PY in uninfected controls, respectively.
"These findings support the possible role of COVID-19 in AA occurrence and exacerbation, although other environmental factors, such as psychological stress, may have also contributed to AA development during the pandemic," the authors concluded. "Plausible mechanisms of AA following COVID-19 include antigenic molecular mimicry between SARS-CoV-2 and hair follicle autoantigens, cytokine shifting, and bystander activation."
They acknowledged certain limitations of the analysis, including the potential for detection or misclassification bias and the fact that it did not evaluate causality between the two conditions.
Shari Lipner, MD, PhD, associate professor of dermatology at Weill Cornell Medicine, New York, who was asked to comment on the study, said that strengths of the study include the large sample size, and the use of positive and negative outcome controls, and that the incidence and prevalence of AA in Korea was stable during the prepandemic period. "A weakness of the study is that all alopecia areata cases may not have necessarily been confirmed," Dr Lipner told this news organization.
"Based on this study, dermatologists may consider AA in the differential diagnosis for a patient presenting with hair loss with recent COVID-19 diagnosis," she added, noting that the potential for prevention of AA flares is also a reason to recommend COVID-19 vaccination for patients with a history of AA.
Christine Ko, MD, professor of dermatology and pathology at Yale University, New Haven, Connecticut, who was also asked to comment on the study, said that while the analysis suggests a definite epidemiologic association between COVID-19 and AA, "any causal relationship needs further study." She added that she has no specific advice for patients who develop AA following a COVID-19 infection. "Any conversation about AA can be difficult because there is no way to prognosticate if someone will just have one small, localized area of hair loss," or several small areas, versus loss of all hair on the head or even the body as well, Dr Ko explained.
The study was supported with grants from the National Research Foundation of the Korean Government and the Ministry of Health and Welfare, Republic of Korea. The authors, as well as Dr Lipner and Dr Ko, reported having no relevant disclosures.
This article originally appeared on MDedge.com, part of the Medscape Professional Network.