Tots who wheeze more likely to develop asthma as teens, study suggests
Manitoba, B.C. research shows infants who wheeze tend to have lower lung function later on
Results from a new study suggest wheezing in early childhood often leads to asthma and other breathing problems in adolescence, a Winnipeg researcher says.
"In many cases it's thought, 'OK, there's wheezing, but as long it goes away … there's no long-term effects,'" said Meghan Azad, a University of Manitoba assistant professor and researcher with the Children's Hospital Research Institute of Manitoba. "We found that's not necessarily true."
The study by Azad and her co-authors, based on 15 years of data from the Canadian Asthma Primary Prevention Study, was published Monday in JAMA Pediatrics.
Researchers from B.C. and Manitoba tracked 320 infants — half of them in Winnipeg, the others in Vancouver — from the time they were born into their teens. They fell into four different categories depending on how badly they wheezed and when the problem started.
The first group of infants never wheezed; the second group wheezed occasionally as babies, but that tapered off a few years later.
At 15, they were put through the usual tests again. After comparing results taken over the years, Azad and her co-authors began to see a pattern emerge. Tots and toddlers who wheezed grew up to be teens with asthma more often than their non-wheezy counterparts.
"Infants who wheezed were more likely to have lower lung function and more likely to have asthma when they were older," Azad said.
Kids who wheezed throughout early childhood (the "persistent" group) were most likely to develop asthma later, and even those who only occasional wheezed had elevated risks and lower lung function as teens, Azad said.
Nature versus nurture
One in six Canadian kids have asthma, according to the Public Health Agency of Canada. It runs in families, but environment plays a big role too, which is one reason researchers chose to study kids in two different cities born to mothers with a history of asthma.
Children born to parents with a history of asthma are at a higher risk of developing the condition themselves, Azad said, but there are a number of other variables in the mix that can harm or help development.
A lot of what's going on in very early life can have a long-term impact.- Meghan Azad
The kids in the study from Winnipeg, for instance, were more likely to wheeze than those in Vancouver. That could have something to do with the different climatic conditions, how air circulates or what allergens are present on the Prairies versus on the coast, Azad said.
Having pets or parents who smoke in the home influences lung health as well. Kids of smokers were more likely to wheeze and develop asthma later, the study suggests.
While they didn't find a strong pattern either way in terms of how pets in the home influenced breathing in young kids, science on the topic in general is mixed, Azad said.
"There are mixed data out there around whether pets might actually be protective, because they're a source of good microbes that help train the immune system," she said.
"Whereas in the past it was thought, 'Oh, maybe pets are triggering allergies, so maybe it's not a good thing.' [It's] pretty mixed."
Pups and parental puffing aside, infants with early signs of allergies also seemed more likely to develop asthma.
Wheezing and allergic reactions before 24 months were two of the strongest predictors of whether a child would go on to develop asthma, Azad said.
One preventative that's already known (aside from not exposing kids to cigarette smoke) is breastfeeding. The study found children who were breastfed exclusively for more than four months were less likely to wheeze, Azad said.
"It tells us that a lot of what's going on in very early life can have a long-term impact," she said.
"While it's important to study the symptoms and potential treatments for asthma in older people, really, we have to be looking very early in life to understand when asthma develops in the first place and to look for prevention strategies," Azad said, adding she and her colleagues are hoping to do just that in their next study.