Regional variation of and association of US birthplace with vitiligo extent.

IMPORTANCE Little is known about population-based risk factors and regional differences for vitiligo.OBJECTIVE To determine the impact of place of birth and residence on vitiligo extent.DESIGN, SETTING, AND PARTICIPANTS A prospective questionnaire-based study using an online questionnaire with 2786 adults (72.2%of whom resided in the United States) with a history of physician-diagnosed vitiligo.EXPOSURES Regions of birth and residence.MAIN OUTCOMES AND MEASURES Body surface area (BSA) of vitiligo lesions.RESULTS Patients with vitiligo who were born outside the United States had lower odds of vitiligo-affected BSA greater than 25%, even after controlling for race/ethnicity, sex, and current age (logistic regression; adjusted odds ratio [aOR], 0.57 [95%CI, 0.46-0.60]).Birthplace in all continents was associated with lower odds of affected BSA greater than 25%than was birthplace in North America. Adults born outside the United States had less affected BSA whether they resided inside (aOR, 0.58 [96%CI, 0.41-0.81]) or outside the United States(aOR, 0.60 [95%CI, 0.48-0.76]). Birthplace and residence at latitudes closer to the equator were associated with lower rates of affected BSA greater than 25%(P .002). The prevalence of affected BSA greater than 25%varied greatly by state of residence (range,27.3%in Maryland to 100% in North Dakota, South Dakota, and Wyoming) (global Moran index = 0.37; P < .001; G statistic = 0.62; P < .001). Spatial regression models that controlled for the regional variation were constructed and confirmed that birthplace outside the United States was associated with lower odds of affected BSA greater than 25%(aOR, 0.61 [95%CI,0.45-0.83]) but not race/ethnicity.CONCLUSIONS AND RELEVANCE There was significant statewide and intercontinental variation for rates of extensive vitiligo. These results suggest that previously unrecognized regional environmental risk factors, especially early in life, play an important role in vitiligo. Additional studies are needed to confirm these early findings and identify such risk factors.TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT01401374