Original article
Epidemiology of alopecia areata, ophiasis, totalis, and universalis: A systematic review and meta-analysis

https://doi.org/10.1016/j.jaad.2019.08.032Get rights and content

Background

Alopecia areata (AA) is a common autoimmune alopecia with heterogeneous severity and distribution. Previous studies found conflicting results about AA epidemiology.

Objective

To determine the prevalence, incidence, and predictors of AA, alopecia totalis, alopecia ophiasis, and alopecia universalis.

Methods

A systematic review of all published cohort and cross-sectional studies that analyzed AA and its subtypes. MEDLINE, Embase, LILACS, Scopus, Cochrane Library, and GREAT were searched. At least 2 reviewers performed study title/abstract review and data extraction. Random-effects meta-analysis was used because of significant heterogeneity (I2 = 99.97%).

Results

Ninety-four studies met the inclusion criteria. The pooled prevalence (95% confidence interval, N) of AA overall was 2.11% (1.82-2.42, N = 302,157,365), with differences of population-based (0.75% [0.49-1.06%], N = 301,173,403) and clinic-based (3.47% [3.01-3.96], N = 983,962) studies. The prevalences of alopecia totalis, ophiasis, and universalis were 0.08% (0.04-0.13, N = 1,088,149), 0.02% (0.00-0.06, N = 1,075,203), and 0.03% (0.01-0.06, N = 1,085,444), respectively. AA prevalence (95% confidence interval) increased over time (<2000: 1.02% [0.85-1.22]; 2000-2009: 1.76% [1.51-2.03]; >2009: 3.22% [2.59-3.92]; P < .0001) and differed by region. AA prevalence was significantly lower in adults (1.47% [1.18-1.80]) than children (1.92% [1.31-2.65]; P < .0001).

Conclusions

AA affects 2% of the global population. AA prevalence is lower in adults than children, is increasing over time, and significantly differs by region.

Section snippets

Literature search

The following databases were searched for articles up to September 1, 2018: Cochrane Library, MEDLINE (PubMed and Ovid), Embase, Latin American and Caribbean Health Sciences (LILACS), and Scopus. The search strategy was modified from a previous Cochrane review6 to include search terms related to AA, AO, AT, and AU (Supplemental Table I; available at https://data.mendeley.com/datasets/publish-confirmation/brbrdwy3pr/1).

Inclusion criteria were any cross-sectional or cohort study that analyzed the

Literature search

Overall, 5185 nonduplicate citations were identified in the database search; 4933 were excluded during title and abstract review, and 159 were excluded during full-text review. In total, 93 observational studies met inclusion/exclusion criteria and were included in the systematic review10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 5, 8, 9, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60,

Discussion

This systematic review and meta-analysis of observational studies found the global prevalence of AA to be approximately 2%, with significant regional variability; fewer than 1 per 1000 persons were affected by AO, AT, or AU. AA was more common in children/adolescents. Finally, the prevalences of AA overall, and of AO, AT and AU in particular, all significantly increased over time. Together, the results indicate that AA is a common disorder affecting patients worldwide and is commonly seen in

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    Funding sources: Supported by the Agency for Healthcare Research and Quality (grant no. K12 HS023011) and the Dermatology Foundation.

    Conflicts of interest: None disclosed.

    Reprints not available from the authors.

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