Table 1. Baseline Characteristics of Primary Alopecia Areata Cohort and Subgroupsa.
| Characteristic | Primary cohort (N = 45 483) | Extent of disease | Dermatologist involvement on diagnosis date | ||||
|---|---|---|---|---|---|---|---|
| With AT or AU (n = 3221) | Without AT or AU (n = 42 262) | SMD | Yes (n = 26 615) | No (n = 18 868) | SMD | ||
| Demographic characteristics | |||||||
| Age, mean (SD), y | 43.8 (14.2) | 46.6 (14.8) | 43.6 (14.2) | 0.40 | 43.8 (14.1) | 43.7 (14.4) | 0.01 |
| Sex | |||||||
| Female | 29 903 (65.7) | 2387 (74.1) | 27 516 (65.1) | 0.18 | 16 922 (63.6) | 12 981 (68.8) | 0.11 |
| Maleb | 15 580 (34.3) | 834 (25.9) | 14 746 (34.9) | NA | 9693 (36.4) | 5881 (31.2) | NA |
| Region | |||||||
| Northeast | 11 921 (26.2) | 856 (26.6) | 11 065 (26.2) | 0.01 | 7663 (28.8) | 4258 (22.6) | 0.14 |
| North Central | 7844 (17.2) | 488 (15.2) | 7356 (17.4) | 0.06 | 4496 (16.9) | 3348 (17.7) | 0.02 |
| South | 18 826 (41.4) | 1457 (45.2) | 17 369 (41.1) | 0.08 | 11 255 (42.3) | 7571 (40.1) | 0.04 |
| West | 6812 (15.0) | 418 (13.0) | 6394 (15.1) | 0.06 | 3182 (12.0) | 3630 (19.2) | 0.20 |
| Unknown | 80 (0.2) | 2 (0.1) | 78 (0.2) | 0.03 | 19 (0.1) | 61 (0.3) | 0.04 |
| Comorbidities | |||||||
| Atopic dermatitis | 1714 (3.8) | 118 (3.7) | 1596 (3.8) | 0.01 | 1223 (4.6) | 491 (2.6) | 0.11 |
| Allergic rhinitis | 5733 (12.6) | 486 (15.1) | 5247 (12.4) | 0.08 | 3305 (12.4) | 2428 (12.9) | 0.02 |
| Asthma | 3236 (7.1) | 248 (7.7) | 2988 (7.1) | 0.02 | 1896 (7.1) | 1340 (7.1) | <0.01 |
| Thyroid disease | 6759 (14.9) | 670 (20.8) | 6089 (14.4) | 0.02 | 3668 (13.8) | 3091 (16.4) | 0.07 |
| Major depressive disorder | 3686 (8.1) | 293 (9.1) | 3393 (8.0) | 0.04 | 1947 (7.3) | 1739 (9.2) | 0.07 |
| Bipolar or manic disorder | 428 (0.9) | 43 (1.3) | 385 (0.9) | 0.04 | 219 (0.8) | 209 (1.1) | 0.03 |
| Anxiety disorder, including OCD | 6136 (13.5) | 496 (15.4) | 5640 (13.3) | 0.06 | 3285 (12.3) | 2851 (15.1) | 0.08 |
| Schizophrenia | 31 (0.1) | 2 (0.1) | 29 (0.1) | <0.01 | 17 (0.1) | 14 (0.1) | <0.01 |
| CCI score, mean (SD) | 0.72 (1.25) | 0.96 (1.53) | 0.70 (1.22) | 0.03 | 0.68 (1.17) | 0.78 (1.35) | 0.01 |
| Medication use | |||||||
| Statin | 5865 (12.9) | 531 (16.5) | 5334 (12.6) | 0.11 | 3425 (12.9) | 2440 (12.9) | <0.01 |
| Ezetimibe-simvastatin | 90 (0.2) | 9 (0.3) | 81 (0.2) | 0.02 | 63 (0.2) | 27 (0.1) | 0.03 |
| High-intensity statin | 1290 (2.8) | 83 (2.6) | 1207 (2.9) | 0.02 | 719 (2.7) | 571 (3.0) | 0.02 |
| Health care use | |||||||
| ED visit | 613 (1.3) | 66 (2.0) | 547 (1.3) | 0.05 | 291 (1.1) | 322 (1.7) | 0.05 |
| Hospitalization | 2339 (5.1) | 253 (7.9) | 2086 (4.9) | 0.12 | 1125 (4.2) | 1214 (6.4) | 0.10 |
| No. of unique medications prescribed, mean (SD) | 13.1 (17.5) | 15.7 (19.3) | 12.9 (17.3) | 0.37 | 12.9 (16.8) | 13.3 (18.4) | 0.04 |
Abbreviations: AT, alopecia totalis; AU, alopecia universalis; CCI, Combined Comorbidity Index; ED, emergency department; NA, not applicable; OCD, obsessive-compulsive disorder; SMD, standardized mean difference.
a
Data are presented in number (percentage) of patients unless otherwise indicated.
b
SMD for male patients was not calculated because gender was treated as a binary variable and female sex was adjusted for in the multivariate model already.