Mice and cockroaches in the home may help prevent asthma, research says

Having creatures like cats, mice and even cockroaches in your home may cut down the risk of your children developing asthma.

That’s according to a new study by the United States National Institutes of Health, which says that children exposed to high levels of pet and pest allergens in the home during infancy end up having a lower risk of developing asthma by the age of seven.

Researchers tracked 442 individuals from birth to seven years of age, all of whom lived in urban US areas, and found that higher concentrations of cockroach, mouse and cat allergens in the living environments during the first three years of life were associated with a lower risk of developing asthma by the age of seven.

Worldwide, asthma rates have been climbing since the 1980s. In Canada, about three million people have the condition which has proven surprisingly difficult to pin down. Although cases of asthma can vary significantly from mild to severe in nature, there is a commonly observed range of symptoms associated with asthma, such as chronic shortness of breath, chest tightness, coughing and wheezing.

But in terms of a cause of the condition, experts are still uncertain. A significant percentage of asthma cases are said to be related to allergic reactions, for example, although this is not always the case. Asthma can be hereditary, as well, yet only in about half of those affected.

So far, health research has offered a number of potential environmental factors that could be contributing to the noticeable increase over the last half century, from rising obesity rates to the stresses of modern life to environmental toxins like pesticides and preservatives in our food.

One prevailing theory that first gained attention in the early 1990s is the hygiene hypothesis, which proposes that the cleanliness of modern living has cut down on infant and childhood exposure to microbes and infectious agents. A good thing, one might assume, yet the hygiene theory contends that early exposure prompts our immune systems to develop stronger defences, effectively training our bodies against future attacks. Without that training, our systems are more easily susceptible to break down in the presence of irritants and in some cases leading to chronic conditions like asthma.

Yet the hygiene hypothesis has had its detractors over the years, who point to the fact that the jump in incidence of asthma started in the 1980s, yet societal changes in sanitary practices occurred decades earlier. As well, studies showed that asthma rates in the United States were increasing most markedly in urban areas, precisely where children were more likely to come into contact with microbes and infections at an early age.

But the new study stands to bolster the hygiene theory, says Dr. James E. Gern, M.D., a professor at the University of Wisconsin-Madison and principal investigator of the study.

“Our observations imply that exposure to a broad variety of indoor allergens, bacteria and bacterial products early in life may reduce the risk of developing asthma,” says Dr. Gern, in a press release. “Additional research may help us identify specific targets for asthma prevention strategies.”