USC Environmental Health Centers

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August 11, 2015

New study finds that risk of asthma and nasal allergy varies by genetic ancestry in Hispanic children

USC Environmental Health

LOS ANGELES - According to the US Census, the Hispanic or Latino population has experienced the fastest growth in the United States and account for more than half of the population growth between 2000 and 2010.  With such trend in population growth, there is a growing need to investigate causes of common health conditions in Hispanic children, who have diverse environmental, socioeconomic, cultural and ancestral backgrounds.

A new study led by Keck School of Medicine of the University of Southern California (USC) researchers set out to investigate the effect of genetic factors on asthma and rhinitis (defined for this study as a problem with sneezing or a runny or blocked nose, when the child does not have a cold or the ‘flu’ also known as “nasal allergy”), two of the most common illnesses in children. They conducted the study among nearly 1800 Hispanic children between the ages of 5 and 7 years who participated in the Southern California Children’s Health Study in 2003.

For a link to the study, click here.

The research indicates that looking at genetic ancestry may help explain the differences in prevalence of asthma and rhinitis within the spectrum of Hispanic people and the burden of asthma and rhinitis in the fast growing, ethnically diverse Hispanic population in the US.

"Studies in the past have generally included multiethnic population with predominantly non-Hispanic population,” said Muhammad T. Salam, adjunct assistant professor of research in the department of preventive medicine at the Keck School of Medicine, and lead author of the research. “While there are common risk factors that affect everyone, we are just beginning to understand that we need to focus on specific Hispanic populations to better understand the complex interplay of genetic, environmental and cultural factors in the development of common health conditions such as asthma and rhinitis."

To determine the ancestral (ethnic) background of each child more precisely, the researchers estimated contributions from Amerindian (ancestral background in Latin American people before 15th century), European, African and Asian ancestry using over 200 DNA sequence variations.
Such variations in DNA (human genome) are genetic markers of ancestry. Certain variants occur in one population or another in the human genome (DNA). When DNA is analyzed in this way, ancestry can be determined at a very precise level depending on how many genetic markers are looked at.

The researchers found lower risk of asthma and rhinitis in people with more Amerindian ancestry.  For each 25% increase in Amerindian ancestry, there was an 18% lower risk of asthma and 14% lower risk of rhinitis.  In children with over 75% Amerindian ancestry, only 9% had asthma and 30% had rhinitis. In contrast, Hispanic children who had less than 25% Amerindian ancestry, 21% had asthma and 44% had rhinitis. The study took into account factors in the environment, culture, and economics.

The parents provided information on their children's health conditions, environmental exposures such as tobacco smoke, allergens, and socioeconomic background. Acculturation is a process by which cultural patterns change when people come in contact with other cultural patterns. The U.S. Hispanic population has undergone such changes over generations. Researchers assessed acculturation based on where the mother was born and what language the parent used to complete the study questionnaire (English or Spanish)

The Southern California Children’s Health Study began in 1993 at USC and was designed to study the chronic effects of air pollution on the developing lungs of Southern California school children.

The research appears in the August 11, 2015 issue of the PLOS ONE. Co-authors include Muhammad T. Salam, M.D., Ph.D. of the Keck School of Medicine of USC, and the Department of Psychiatry, Kern Medical Center; Tigran Avoundjian, M.P.H. of US Department of Veterans Affairs, Center for Health Care Evaluation; Wendy M. Knight MPH, of the Los Angeles County Department of Public Health, Acute Communicable Disease Control Program; and Frank D. Gilliland, M.D., Ph.D. of the Keck School of Medicine of USC

The collaborative study was funded by the National Heart, Lung and Blood Institute (grants 5R01HL61768 and 5R01HL76647); the Southern California Environmental Health Sciences Center (grant 5P30ES007048) funded by the National Institute of Environmental Health Sciences; the Children’s Environmental Health Center (grants 5P01ES009581, R826708-01, and RD831861-01) funded by the National Institute of Environmental Health Sciences and the Environmental Protection Agency; the National Institute of Environmental Health Sciences (grants 5P01ES011627); and the Hastings Foundation.

Article Cited:
Salam, M.T., Avoundjian, T., Knight, W.M., & Gilliland, F.D. (2015). Genetic ancestry and asthma and rhinitis occurrence in Hispanic children: Findings from the Southern California Children's Health Study. PLOS ONE Published online August 11, 2015; doi: 10.1371/journal.pone.0135384

Contact: Muhammad T. Salam,

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