How dogs can reduce the risk of childhood asthma

By Adem Lewis / in , , , , , , , , , , , , , /

Childhood asthma is a major concern, affecting
around 8% of children in the US, and rates are on the rise. The “hygiene hypothesis” suggests that
our increasingly clean lifestyles are altering the way our immune systems develop. Without the constant, low-level exposure to
microbes, we are shifted to a more allergic phenotype. Having recently adopted a puppy, I can personally
tell you that dogs are a constant source of microbe exposure. But to date, data on early childhood exposure
to dogs is mixed. Does the dander promote allergy and thus asthma,
or do their loveable, bacteria-filled mouths offer some form of protection. It’s a tough question to answer. You don’t want to rely on self-report of
prior dog ownership – that can be inaccurate. But where in the world can you find a registry
of every dog owner? Well, Sweden, it turns out. In addition to having a national health care
system and data registry, they also require registration of all pet dogs. Apparently, something like 80% of all dogs
in the country are part of the registry, so finally we are in a position to determine
if dog-ownership increases or reduces the risk of childhood asthma. The study, appearing in JAMA Pediatrics, examined
the roughly 1 million children born in Sweden between 2001 and 2010. In their seventh year of life, 4.2% of them
had an asthma attack. Overall, around 8% of kids had a dog in the
home during their first year of life. So how did these percentages relate? Well, the kids with the dogs were about 8%
less likely to develop asthma. But wait a minute, there are a bunch of confounders
at play here. What if parents with asthma avoid getting
dogs and are more likely to have kids with asthma? What if an older sibling with asthma prompts
the family to get rid of the dog? What if people in lower socioeconomic strata
are less likely to own a dog and more likely to develop asthma for other reasons? The authors did a commendable job of controlling
for these factors, actually, and if anything the protective effect of dog-ownership grew. But one big issue remains. While 80% dog registration is amazing (by
American standards), that means that 20% of people have unregistered dogs. If those individuals are also more likely
to develop asthma, it could blow the whole effect we are seeing. It turns out that dogs are not the most protective
animal though. Exposure to farm animals was far more protective
– reducing the rates of asthma by about 50%. The bottom line here is that if you’re debating
getting a dog, don’t let fear of childhood asthma stop you. But if you remain concerned, perhaps consider
adopting a family cow.

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