Worldwide, a quarter million people die from the disease each year. And no one knows exactly what causes it. 

Understanding the origins of asthma and allergy is the major focus of the CHILD (Canadian Healthy Infant Longitudinal Development) Study, launched in 2008 as a collaboration between the Canadian Institutes of Health Research and the AllerGen NCE research network. 

A look at the CHILD Study

With more than 3,000 families participating across the country, this is the largest hands-on birth cohort study to have ever been conducted in Canada. CHILD looks at how the environment that a child is exposed to during pregnancy and in the first few years of life can interact with genetics to cause allergies, asthma and other chronic diseases. “We recruited mothers during their pregnancies and have followed these families after birth into their home environments, and through childhood to age five years,” says CHILD Study Director and McMaster University professor Malcolm Sears. “Some studies have simply collected data from health records and databases, but we have interacted directly with the children and their families.” 

It only makes sense that asthma and children’s allergies would be the primary focus of such a landmark study. “If kids can’t breathe,” points out Study Co-Director Padmaja Subbarao, “they can’t play or learn or do any of the normal things kids should be doing.”

The role of the environment in asthma prevention

And there’s reason to hope that asthma may be preventable. “If you look at identical twins,” says Dr. Subbarao, a pediatric respirologist at The Hospital for Sick Children, “sometimes only one twin in a twin set will develop asthma, suggesting that environmental factors may influence the genetics.” 

One of the main discoveries to come out of the CHILD Study thus far casts a new light on an old theory about these environmental factors. This theory, known as the “hygiene hypothesis,” dates back to the early 1990s and puts forth that an excessively clean and sterile environment increased the risk for allergies and asthma. If true, it would help explain why both are much more prevalent in developed countries than in the developing world.

“I’d much rather find an environmental solution than give children medicine which might have side effects. But, yes, there is the possibility of a deliberate intervention to introduce missing microbes, such as through specific probiotics, even if not exactly a vaccine.”

Early risk factors

The CHILD Study has found solid evidence not only supporting the hygiene hypothesis, but illuminating the mechanism behind it. A wide range of helpful bacteria and microbes, known collectively as “gut flora,” live in our stomachs, and studies have shown a strong connection between changes in gut flora and immune diseases like asthma. In the CHILD Study, for the first time, it’s been shown that known early risk factors for asthma, like birth by caesarean section, result in an infant’s gut flora lacking certain specific microbes. Similarly, beneficial microbe colonization, which could potentially protect against childhood asthma and allergies, has been found from exposures like breastfeeding, living with household pets, and playing with older siblings.

Simple actions can help to safeguard children

Encouragingly, this means parents might have the power to help guard their kids against asthma and allergies through simple changes, like increasing outdoor play. “People should not wrap their children up in a sterile environment and try to protect them from dirt,” says Dr. Sears. Expanding this idea further, CHILD researchers hope that their results might influence public policy and even urban planning, helping to build cities that naturally keep us healthier. 

The other side to the coin is the possibility of probiotic intervention. Does this mean an asthma vaccine is around the corner? “As a pediatrician,” says Dr. Stuart Turvey, leader of the Vancouver site of the CHILD Study, “I’d much rather find an environmental solution than give children medicine which might have side effects. But, yes, there is the possibility of a deliberate intervention to introduce missing microbes, such as through specific probiotics, even if not exactly a vaccine.”

A progressive, hopeful journey ahead

Of course, there is more work to do, and that work requires ongoing funding. If the CHILD Study is able to follow their cohort into adulthood, they expect further breakthroughs not only in regards to asthma and allergies, but also other chronic conditions such as type 2 diabetes, obesity, and mental illness. “We’re still in the early days of a very significant study,” Dr. Sears says with conviction and optimism.