Exposures in Mexico may prevent childhood asthma

Published Online: August 18, 2016

Development of asthma has been strongly linked to early life or prenatal environmental exposures. Population-based national surveys have previously shown that Mexican-born children living in the United States have a lower prevalence of asthma than Mexican American children born in the US. This protective effect appears to be reduced by acculturation, younger age at time of immigration, and longer duration of time in the US, suggesting that early childhood exposures in Mexico may provide protection from asthma.

Tucson, Arizona is located approximately 110 kilometers north of the sister cities of Nogales, AZ and Nogales, Sonora, Mexico which straddle the US-Mexico border. Despite this geographic proximity, infrastructural and social differences across the international border may result in differences in exposures and disease prevalence. Researchers from the University of Arizona College of Medicine and Mel and Enid Zuckerman College of Public Health hypothesized that asthma prevalence would indeed differ among these communities.

In a recent article published in The Journal of Allergy and Clinical Immunology: In Practice, Carr and colleagues present results of a binational study assessing the prevalence of asthma diagnosis and symptoms among schoolchildren 13-14 years of age living across the US-Mexico border. The authors administered the International Study of Asthma and Allergy in Children (ISAAC) asthma questionnaires to 1753 middle school children n 5 public schools spanning Tucson, AZ, Nogales AZ, and Nogales, Sonora, Mexico.

Despite similar ethnic background and limited geographic region, Mexican-American children attending middle school in Tucson and Nogales, AZ reported a substantially higher prevalence of asthma symptoms and diagnosis than Mexican children attending middle school in Nogales, Sonora, Mexico. The odds of having diagnosed asthma were more than fourfold in Tucson compared with the reference school in Sonora, and the odds of having active wheezing in Tucson was more than twofold that of Mexico. The school with the lowest prevalence of asthma also represented the community of lowest socioeconomic status and least infrastructure.

These differences in asthma prevalence, in a population of adolescents from similar ethnic background, suggest that environmental factors contribute to this gradient in a complex way, potentially influenced by socioeconomic status, education, and acculturation. Understanding these environmental factors could lead to new methods of decreasing asthma risk and improving population health.

The Journal of Allergy and Clinical Immunology: In Practice is an official journal of the AAAAI, focusing on practical information for the practicing clinician.

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