Asthma is a respiratory condition that affects seven million children and 18 million adults. The disease affects the lungs and swells the airways, making breathing difficult and causing coughing, wheezing, and shortness of breath. It can even be debilitating, as triggers can be a variety of everyday things that affect breathing like allergens including pollen, pet dander, mold, and dust, as well as tobacco smoke, air pollution, strong emotions, and exercise.

Currently, there is no cure for asthma, but research has shown that about half of the children diagnosed with asthma grow out of it by the time they reach adulthood. A new study has established a way to genetically test whether a child can grow out of asthma, independent of family history of asthma and other respiratory disorders.

In a study of 880 children with asthma, researchers measured the children's genetic risk of asthma as well as the severity of their asthma diagnosis form the ages of three to 38. Their asthma severity was measured by symptoms as well as missed days of school or work as well as hospitalizations. Their genetic risk for asthma was measured by severity compared to genome-wide association studies (GWAS). The GWAS identified parts of participants' DNA, or genome, which predisposed them to asthma. Higher genetic risk was characterized by many of these genetic indicators of asthma, while lower genetic risk was characterized by fewer genetic indicators of asthma.

They found that people with higher genetic risk toward asthma also had the most severe symptoms. Those with higher genetic risks had atopy, or sensitivity to asthma triggers, airway constriction, and irreversible airflow obstruction. Many of these issues related to asthma go hand in hand; 72 percent of the studied children illustrated a substantial overlap between the development of atopy and airflow obstruction.

Children with high genetic risk and these dangerous symptoms were more likely to develop persistent asthma that would last into adulthood, especially if their asthma began before the age of 13. Researchers also found that those with higher genetic risk developed asthma at a younger age than those with a low genetic risk for asthma.

Similarly, those with high genetic risk for asthma missed more days of school and work and were hospitalized for asthma-related issues more than the low genetic risk group. Those who had greater genetic risk still had asthma into adulthood, while 10 percent fewer people with childhood asthma had asthma as adults when they had lower genetic risk. This result, while seemingly insignificant, indicated that given lower severity and lower genetic predisposition toward asthma, some people eventually stop suffering from it.

James T C Li, M.D., Ph.D., answering a question for the Mayo Clinic about children outgrowing asthma, said, "In some children, asthma improves during adolescence and young adulthood. For others, symptoms go away only to return a few years later. Many children with asthma never outgrow it." However, bsaed on the findings of this study and the debilitating effects of asthma, parents should take every precaution to ensure their child's health and not count on them to outgrow it. "Work with your child's doctor to make certain you're taking the right steps to manage your child's asthma. This generally includes following a written asthma action plan to systematically track symptoms, adjust medications and help your child avoid asthma triggers," Li suggested.

Researchers found that family-based genetic risk for asthma is unrelated to an individual's genetic risk. The genetic risk that they measured does not take into account one's family history of asthma. This is innovative, as family history does not necessarily indicate the likelihood that a person will encounter asthma triggers, or even respond to them. An individual's genetic risk, on the other hand, does indicate much about a person's asthma risk, as it is based only on that person and his or her lung development.

Daniel Belsky, Ph.D., leader of the study, concluded, "Although our study revealed that genetic risks can help to predict which childhood-onset asthma cases remit and which become life-course-persistent, genetic risk prediction for asthma is still in its infancy. As additional risk genes are discovered, the value of genetic assessments is likely to improve. But our predictions are not sufficiently sensitive or specific to support their use in routine clinical practice."

 

Source: Belsky DW, Sears MR, Hancox RJ, et al. Polygenic risk and the development and course of asthma: an analysis of data from a four-decade longitudinal study. Lancet. 2013.