To the Editor.—
No estimates of the incidence or prevalence of alopecia areata (AA) have been published. The First National Health and Nutrition Examination Survey (NHANES-I), conducted from 1971 through 1974, contained a dermatologic examination of 20 749 individuals in a probability sample of the US population. This communication presents the prevalence of AA as estimated from the findings of NHANES-I.
Materials and Methods.—
The survey design and methods of NHANES-I have been well described by the National Center for Health Statistics (NCHS).1,2 The examiner's diagnosis of AA could be recorded in four places on the survey form as follows: (1) "significant dermatological diagnosis" (limit of three); (2) a finding on the scalp; (3) a finding on the face; or (4) a finding on the nail.Using a published table of upper- and lower-bound factors based on the Poisson distribution,3 95% confidence intervals (CIs) for total prevalence and