While progress has been made in identifying genes associated with asthma, the disease is complex, and its development is likely dependent upon both genetics and environmental exposures, according to a leading expert presenting at the annual meeting of the American College of Allergy, Asthma and Immunology (ACAAI) in Miami Beach, Fla.
On one hand, 39 potential "asthma genes" have been identified. Yet, for nearly every gene found to be negatively associated with asthma in one study, other studies have failed to replicate the findings.
"This suggests that the effect of these genes on allergic diseases is not direct and simple," said Fernando D. Martinez, M.D., director of Arizona Respiratory Center, interim director of the BIO5 Institute and Swift-McNear Professor of Pediatrics at the University of Arizona in Tucson, Ariz. "Many genetic variants associated with asthma will not increase the risk of the disease in all persons. Most will modulate the effects of environmental exposures, making certain subjects more or less susceptible."
With respect to environmental exposures worsening asthma, Dr. Martinez highlights viral infections, passive smoking and air pollution.
But the impact of all environmental factors isn't necessarily obvious. Some exposures play a protective role. "For example, in farming communities where exposure to microbial products is high, children have significantly less asthma and allergies," said Dr. Martinez.