This cross-sectional study evaluated disparities in the prevalence of AA in a racial/ethnically diverse population. A higher burden of AA was observed among skin of color. Additionally, participants with lower education and household income and no health insurance were less likely to be diagnosed with AA.
The higher prevalence of AA among skin of color participants demonstrated in our study is consistent with findings of other US studies.3-5 Prior studies have found increased odds of AA among Blacks and Hispanics, consistent with our findings.3-5 For example, an analysis of 14,400 visits for AA from the National Ambulatory Medical Care Survey between 2007 and 2016 showed increased likelihood of non-White individuals visiting for AA compared to White individuals (OR, 2.4; 95% CI, 1.2-5.1; P = 0.02).5
Studies on the overall prevalence of AA are scarce, and estimates vary widely. The most frequently referenced study is the 1971–1974 First National Health and Nutrition Examination Survey, which estimated the period prevalence of AA in the US to be between 0.1% and 0.2%.7 However, two recent studies in Greece and Japan reported period prevalence of 1.27% and 2.45%, respectively.8, 9 Recently in 2020, a large cross-sectional online survey of the prevalence of AA in the US reported a clinician-adjudicated point prevalence of 0.21% (95% CI, 0.17%-0.25%), while we report an overall prevalence of 0.30% (95% CI, 0.28–0.32).10 The increased prevalence of AA in individuals with skin of color and the high level of diversity in the AoU database may partly explain that our estimated prevalence of AA is slightly higher than that reported by other US-based studies, such as the aforementioned online survey, which included 77.1% white and 13.3% black participants.10
The underlying cause of the increased prevalence of AA in skin of color has yet to be elucidated. Other immune-mediated diseases known to be associated with AA, such as systemic lupus erythematosus (SLE), disproportionately affect Blacks and Hispanics and may have shared aspects of pathophysiology with AA.11 Cohort studies evaluating racial disparities in SLE have identified specific genetic susceptibility loci that differ by racial or ethnic background. For example, higher IFN-α activity has been observed among Black patients with SLE.12 Notably, several case reports have reported AA as a side effect of IFN-α therapy, and expression of type 1 interferon-related proteins in inflammatory lesions of AA has been demonstrated.12
Similar to prior studies, we found a higher prevalence of AA in females compared to males. Two studies evaluating incidence of AA in the US reported similar higher incidence in women than in men.13, 14 However, a cross-sectional analysis of an estimated 2.6 million AA outpatient visits from the National Ambulatory Medical Care Survey and National Hospital Ambulatory Medical Care Survey revealed that males made fewer clinic visits per 1,000 capita compared to females.15 Additionally, in a US study of 481 Caucasian patients from AA patient conferences, there was a female predominance of AA (female to male ratio 2.3:1),16 and a Turkish study reported that 53.4% of patients diagnosed as having AA, AT, or AU were female and 46.6% were male.17
Associations of AA with LGBTQIA+ status, physical disability, socioeconomic status, education level, or health insurance status have not been evaluated in prior epidemiological studies. While LGBTQIA+ status and AA and physical disability were not associated with AA, we found decreased odds of AA in participants without health insurance and those with lower education and lower income. These findings may indicate limited access to dermatologic care in these populations. As a result, AA may be underdiagnosed in these populations, leading to increased morbidity and decreased health-related quality of life.18 This is supported by the increased prevalence of AA in the AoU database, which is focused on the inclusion of underrepresented populations, compared to other AA prevalence studies.10 As such, our findings reinforce the theorized lack of access to dermatologic care among populations at lower socioeconomic status and emphasize the need for improved healthcare access.19
When participants lacking health insurance were excluded from analysis, all associations stayed similarly, indicating that lack of health insurance does not account for the decreased likelihood of AA diagnosis in participants with less education and lower annual income. Rather, these factors appear to be independently associated with decreased odds of being diagnosed with AA, pointing to underdiagnosis and lack of access to dermatologic care among these vulnerable populations.
Our study had several strengths. This study benefits from the diversity of the AoU database and its commitment to including individuals from underrepresented populations. As a result, we were able to evaluate the burden of AA in a national cohort that reflects the diversity of the US population. We evaluated a large sample size of 251,597 participants with available EHR data and were able to adjust for numerous demographic factors that have been suggested as risk factors of AA risk in underrepresented racial and ethnic groups, such as socioeconomic status, educational attainment, physical disability, and health insurance status.4 We also adjusted for co-occurrence of other autoimmune skin conditions and thyrotoxicosis, which are known comorbidities of AA.4 Since our analysis takes notable potential confounders into account, our study is one of the first to demonstrate that there is an increased burden of AA in underrepresented racial and ethnic groups, regardless of socioeconomic differences.
Our study was subject to the limitations of a cross-sectional design. Additionally, opt-in databases such as AOU are subject to selection bias. Another limitation of our study was the small sample size of participants diagnosed with AT and AU, so we were unable to determine whether underrepresented groups experience more severe AA subtypes compared to the general population. This potential relationship merits evaluation in future studies with a larger number of AT and AU participants. Finally, we were not able to evaluate age at diagnosis of AA because AoU data provides only age at the time of enrollment.
In conclusion, our findings regarding the epidemiology of AA are generally consistent with prior studies, validating the scientific consistency of the AoU database and indicate its usefulness for evaluating the epidemiology of dermatologic diseases. Specifically, we confirmed that the increased prevalence of AA among underrepresented racial and ethnic groups persists, even after adjustment for socioeconomic status, educational attainment, physical disability, and health insurance status. Additionally, we found significantly decreased odds of AA diagnosis in participants without health insurance and those with low education and household income. These findings suggest that AA may be underdiagnosed in these populations, potentially mediated by limited access to dermatologic care. Future studies are needed to further replicate these associations and elucidate their underlying causes.