PURPOSE OF THE STUDY.
The goal of this study was to determine whether the prevalence of allergic diseases is lower in foreign-born Americans and if prevalence increases with prolonged residence in the United States.
Data were collected for 91 642 children ages 0 to 17 years in the 2007–2008 National Survey of Children’s Health. A total of 79 667 participants were analyzed.
Random telephone numbers were selected for administration of the questionnaire, which was conducted in English, Spanish, and 4 Asian languages (Korean, Mandarin, Cantonese, and Vietnamese).
Children born outside the United States compared with those born within the United States had significantly lower prevalence of allergic disorders (20.3% vs 34.5%; logistic regression odds ratio [OR]: 0.48 [95% confidence interval (CI): 0.38–0.61]; P < .001). Among children born outside the United States, children with foreign-born parents had significantly lower odds of atopic disease than those with US-born parents (18.2% vs 33.4%; logistic regression OR: 0.45 [95% CI: 0.25–0.78]; P = .005). Furthermore, there was an additive effect in which children of 2 foreign-born parents had a lower prevalence of allergic disease than those with 1 foreign-born parent. Among foreign-born children, children who lived in the United States for >10 years, compared with those who resided in the United States for only 0 to 2 years, had significantly higher odds of developing allergic diseases (adjusted OR: 3.04 [95% CI: 1.08–8.60]), specifically eczema and hay fever but not asthma or food allergy. Age at the time of immigration was not associated with lower odds of any allergic disorders.
The findings from this large, prospective, US population–based study suggest that either infections or certain microbial exposures in early childhood may confer protection against atopic disorders. However, because the odds of developing allergic disease dramatically increase after a decade of living in the United States, protective effects may not be lifelong.
These findings further support the role of environmental factors in the development of allergic disease. Limitations of this study, however, include self-report of allergic disease without clinical verification. The majority of the participants currently reside in a metropolitan area, and it is unknown what proportion of foreign-born families moved from a developing country (compared with an industrialized country) to the United States. Country of origin was not ascertained, although race/ethnicity data were collected as a proxy. Other potential confounding factors not evaluated include diet, allergenic exposures, use of antibiotics, use of antibacterial cleaning products, and history of helminthic infections.
- Copyright © 2014 by the American Academy of Pediatrics