Puerto Rican children with asthma are more likely to be exposed to violence and to have changes in a gene that is associated with stress, according to a new study led by researchers at Children’s Hospital of Pittsburgh of UPMC and the University of Pittsburgh School of Medicine.

Researchers recruited children ages 6 to 14 years who had four Puerto Rican grandparents from randomly selected San Juan households. Of the participants, 271 children had physician-diagnosed asthma and wheeze in the prior year and 266 did not have asthma or a history of wheezing. Blood samples were drawn for DNA analysis, all parents completed a questionnaire and children 9 years and older answered another standard questionnaire about exposure to violence.

Scientists looked for evidence of a biochemical process called methylation of the promoter (or “on-off” switch) of a gene called ADCYAP1R1, which previous studies have linked to PTSD, according to researchers.

“Recently, there was a University of California study that showed traumatic life experiences affect a certain gene product involved in cellular stress responses in adults and was linked to a higher risk of post-traumatic stress disorder or PTSD,” said Juan C. Celedón, MD, DrPH, the Children’s Hospital of Pittsburgh of UPMC’s chief of Pediatric Pulmonology, Allergy and Immunology. “We wanted to see whether similar gene alterations could be found among Puerto Rican children with asthma.”

Analysis found that increased methylation was associated with higher odds of having asthma and with exposure to violence, and that increasing exposure to violence was linked with a greater risk of asthma, according to the study. A certain variation (or polymorphism) in the ADCYAP1R1 gene in study participants was also associated with asthma, but not with methylation.

“It appears there is a subgroup of people who may be more susceptible to asthma because of exposure to violence, and we need to understand how that happens,” Celedón said. “Most asthma studies have focused on environmental factors such as air pollution. This is one of the first to look at the impact of stress on epigenetics, which can cause differences in gene expression.”

The study, which is the first to examine the links between asthma, stress and gene variation, was recently published in the American Journal of Respiratory and Critical Care Medicine.