Published Online: October 6, 2014
Among children in the United States, the two extremes of asthma prevalence and mortality are represented by Hispanic/Latino populations, with Puerto Ricans having the highest and Mexicans the lowest. Although environmental factors are important, Puerto Ricans and Mexicans vary greatly in their genetic ancestry, which may also contribute to asthma disparities.
In a study recently published in The Journal of Allergy and Clinical Immunology (JACI), M. Pino-Yanes and colleagues present results from the largest, most comprehensive study of genetic ancestry, asthma susceptibility, and lung function in Latinos to date. The authors examined 5,493 Latino children with and without asthma from three independent studies: the Genes-environments & Admixture in Latino Americans study (GALA II), the Genetics of Asthma in Latino Americans study (GALA I), and the Children's Health Study (CHS). Genetic ancestry was assessed using genotypes at hundreds of thousands of polymorphic sites scattered throughout the genome, to obtain genomic proportions of African, European and Native American ancestry in all study participants. The authors then tested for an association between genetic ancestry and asthma susceptibility, and with different measures of lung function. Environmental factors including current and early life exposure to air pollution and tobacco smoke, socioeconomic status, discrimination, and acculturation were also taken into consideration.
The authors demonstrated that for every 20% increase in Native American ancestry, the odds of developing asthma was 43% lower in Mexicans and other Latinos, but not among Puerto Ricans. In contrast, African ancestry was correlated with increased odds of asthma in Puerto Ricans and other non-Mexican Latinos, with every 20% increase corresponding to a 40% increase in risk. These results did not change when environmental or socioeconomic factors were taken into account, suggesting that genetic differences are the primary cause. In addition, the authors report that measures of lung function among children with asthma were higher in Mexicans, intermediate in other Latinos and lowest in Puerto Ricans. These differences were fully explained by differences in the proportion of African and Native American ancestry, with increasing African ancestry correlating to lower lung function and increasing Native American ancestry to higher lung function.
Overall, M. Pino-Yanes and colleagues demonstrate that disparities in asthma prevalence and lung function among Latinos can be partially explained by differences in genetic ancestry, independent of early life exposures and socioeconomic status. These findings are clinically relevant, as the current method for predicting lung function in Puerto Ricans relies on spirometry reference equations derived from Mexicans or Whites. Puerto Ricans will therefore benefit from the development of population-specific reference equations. Lastly, their results demonstrate that not just environmental, but genetic, differences between diverse Latino populations play an important role in asthma susceptibility and differences in lung function.
The Journal of Allergy and Clinical Immunology (JACI) is an official scientific journal of the AAAAI, and is the most-cited journal in the field of allergy and clinical immunology.