A growing body of evidence links perinatal exposures, such as respiratory viral infections, medications, and environmental substances, to increased risk of childhood asthma. Investigator, Christian Rosas-Salazar, MD, MPH, Assistant Professor of Pediatric Allergy, Immunology, and Pulmonary Medicine at Vanderbilt University, has explored exposures of asthma risk ranging from respiratory syncytial virus (RSV) infection and antibiotic use to environmental allergens and breastfeeding. He discussed potential clinical impacts with the CHEST Physician publication. The interview has been edited for clarity.
CHEST Physician: What types of exposures seem to be the most problematic for childhood asthma risk?
Dr. Rosas-Salazar: The first thing to consider is that asthma is not a single condition but a collection of many similar diseases that are grouped under the same umbrella term. You can imagine that we are going to have different risk factors for different subtypes of asthma. However, early life respiratory infections with RSV, obesity, environmental pollution, antibiotic use, and exposure to tobacco smoke in utero or after birth are among the most common exposures that have been shown to increase the risk of asthma later during childhood.
CHEST Physician: Are there specific time periods when exposures seem to carry greater risk for later asthma?
Dr. Rosas-Salazar: That depends on the specific exposure. Some exposures have been shown to be more problematic during the prenatal stage, while other exposures can be more harmful when occurring after a child is born. In some other cases, it can be both. One example is exposure to tobacco smoke. Both in utero exposure and exposure during the first year of life have been associated with an increased risk of asthma. It depends on the type of exposure and, likely, the subtype of asthma.
There are also critical windows when the child is more vulnerable to certain exposures. In general, those are the prenatal period and the first year of life, when the immune response and lungs are still developing.
CHEST Physician: What mechanisms link exposures and asthma risk?
Dr. Rosas-Salazar: That, again, depends on the exposure. Different exposures may have different mechanisms that can lead to asthma.
You can imagine that the pathways that link prenatal tobacco smoke exposure to asthma development are very different than those mechanisms that explain the association of RSV during infancy with asthma onset. In general, we think most of these early life exposures change the immune response (the way the child responds to respiratory viruses, allergens, or other triggers) and how their lungs work, making a child more prone to developing asthma.
CHEST Physician: One of the more interesting exposures is antibiotics since antibiotic use is so common in prenatal care and childhood infections. What are the mechanisms?
Dr. Rosas-Salazar: The main line of thought is that early life antibiotic use disrupts the developing microbiome. Killing beneficial bacteria or increasing the abundance of harmful bacteria can lead to changes in the immune response, which later lead to the development of asthma. We are now looking at specific microbial pathways that can explain the relationship between early life antibiotic use and asthma risk. The ultimate goal is to design potential interventions that could change the microbiome or prevent microbiome changes after antibiotic use to decrease the risk of asthma in children exposed to antibiotics in the first few years of life.
CHEST Physician: How can clinicians help reduce exposures that may contribute to asthma?
Dr. Rosas-Salazar: Health care providers should continue to encourage breastfeeding, which has been associated with a decreased risk of asthma in many studies. This should be recommended not only for its respiratory benefits but also for the many nonrespiratory benefits that breastfeeding has.
Additionally, we should encourage a healthy lifestyle, like maintaining adequate weight—especially in the first few years of life—and avoiding tobacco smoke exposure both during pregnancy and after. We should encourage women who are pregnant to have adequate prenatal care to minimize the risk factors for prematurity, which is one of the exposures we know can increase the risk of asthma.
We should also be mindful of prescribing antibiotics in early life. Antibiotics have so many benefits and have been crucial in improving childhood health, yet they are frequently misused for diseases that do not require antibiotics, such as respiratory viral infections. Decreasing the misuse of antibiotics in infancy would potentially have a beneficial effect on asthma prevalence at the community level.