1. Foreign born adults with vitiligo self-reported lower affected body surface area (BSA) when compared with native born US adults.
2. Either being born or having resided in regions closer to the equator appeared to be a positive prognostic factor for vitiligo extent.
Evidence Rating Level: 2 (Good)
Study Rundown: The pathogenesis of vitiligo, which is thought to result from immune-mediated attack of melanocytes, is relatively well studied. In contrast, little is known about the epidemiological risk and prognostic factors for the development of the disease and the extent of vitiligo BSA involvement, respectively. In this study, authors sought to identify trends in population-based risk factors and regional differences for vitiligo. After controlling for potentially confounding variables (e.g. race, sex, current age, and age at vitiligo onset), being born outside of the US, being born near the equator, or residing near the equator associated with a lower odds of vitiligo BSA greater than 25%. A strength of this study was the large and diverse sample size attained, though limitations did exist. One such limitation was a potential self-selection bias of the questionnaire respondents due to surveying vitiligo support groups.
In-Depth [prospective cohort]: Members from nonprofit support groups for vitiligo vulgaris were invited to participate in a 77-question survey, and 2786 responses were analyzed. Logistic regression models were built to determine effects of country of birthplace and present residence on BSA affected. To account for countries with few respondents, composite variables were created, and adjusted odds ratios were calculated for multivariate models. 72.2% of respondents currently resided in the US, and similarly, 62.8% of respondents reported a birthplace within the US. Individuals born outside the US had significantly lower odds of affected BSA > 25% (logistic regression; OR, 0.52 [95% CI, 0.44-0.61]; p < 0.001). This association remained significant, even in multivariate models (p < 0.001) and whether they currently lived inside (OR, 0.52 [95% CI, 0.4-0.67]; p < 0.001) or outside (OR, 0.52 [95% CI, 0.43-0.62]; p < 0.001) the United States. Individuals born or residing in regions with latitudes between -24 and 24 degrees were less likely to have affected BSA > 25% (birthplace: 7.1% vs 13.0%, p < 0.001; residence: 3.0% vs 5.5%, p = 0.002).
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