Perspective
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Jonathan Spergel, MD, PhD
It is important to look for the risk factors for atopic diseases. Why are they rising? This is a large longitudinal study with 47,000 kids. The researchers followed them for a long time, and their findings are consistent with what other people have found.
Early infections are probably protective. That is why going to daycare, being around other people and having older siblings are all part of the hygiene hypothesis. You need to be around other people to get the appropriate number of good germs. That is one of this study’s big findings.
Another is that preterm birth is a risk factor, probably due to lots of different things. Premature lungs are likely a risk factor by themselves for asthma because they have a disrupted barrier.
These findings are all consistent with the hygiene hypothesis. They also are confirmatory and along the same lines of other studies.
This is what we see in practice. Certain things are protective. It gets complicated because there is a genetic component too. As allergists, we always get a bias, because we see people who already have allergies. We see their siblings, and their siblings have asthma. Our patients have genetic risk factors. In a general population, this is very consistent with what we have seen in other research studies.
This study identified three risk factors for asthma early on – premature birth, early infection and rapid weight gain. If you have patients who were premature or obese or were admitted to the hospital for respiratory infection early in their lives, that probably is going to be a risk factor for asthma.
But we do not know if that initial hospitalization by itself causes asthma or if these people were predisposed to these first infections. We all get respiratory syncytial virus (RSV). Maybe that RSV leads these people to be hospitalized, whereas someone who is not at risk for asthma would not be hospitalized. There is a little controversy in that issue right now. Does infection cause asthma, or is it just a marker?
But from a clinical perspective, these findings tell you that these are the people you should look for. You can’t tell people to have more siblings. But you can tell them that preschool may be a good thing and to send their kids to pre-K.
There are still some important questions to answer. What in daycare is different? What is so different about having multiple siblings? Are these patients more exposed to more colds early on? Is that the issue? Or is it a change in their microbiome? These are important questions to ask.
Jonathan Spergel, MD, PhD
Director of the Food Allergy Center / Center for Pediatric Eosinophilic Disorders
Chief of the Allergy Section, Division of Allergy and Immunology
Stuart E. Starr Chair of Pediatrics
Professor of Pediatrics
Children’s Hospital of Philadelphia
Disclosures: Spergel reports receiving dupilumab and institutional grant support from Regeneron Pharmaceuticals and Sanofi Genzyme for previous studies.