Playing in the Dirt

 Posted by on 30 September 2005 at 10:57 pm  Uncategorized
Sep 302005

Over the years, I’ve had a passing curiosity in the search for the causes of human diseases that substantially reduce a person’s reproductive fitness without modern medicine, such as allergies, asthma, diabetes, and so on. One interesting hypothesis for some diseases is the “hygiene hypothesis.” It “proposes that reduced microbial exposure because of improved sanitation and cleaner lifestyles has facilitated the rise in asthma, allergic disease and multiple sclerosis in the Western world.” Basically, the idea is that the immune system of a child needs to be exposed to all manner of crap to prepare itself to perform its job well later in life.

So I was interested to read that the hypothesis might be able to explain the high incidence of heart disease. The article reports:

Early childhood viral infections might reduce the risk of developing heart disease later in life by as much as 90 percent, researchers from Sweden and Finland reported… According to the investigators, “improved hygiene in early childhood might partially explain the greatest epidemic of the 20th century — coronary heart disease.” It is the first time that the so-called “hygiene hypothesis” has been linked to the development of heart disease… [Researchers] found a consistent trend between the number of childhood infections and the reduction in coronary risk. For instance, having two childhood viral infections reduced the coronary risk by 40 percent; four infections was associated with a 60-percent decreased risk; and six infections lowered the risk by 90 percent.

One of the researchers rightly cautioned not to read too much into these preliminary findings: “We need to do more studies about the influence of the immune system on the cardiovascular system.”

To be fair, my interest in this hypothesis might just be wishful thinking, since I played in lots of dirt on the family horse farm as a child. If my three long-deceased biological grandparents are any indication, I’m not doing so well in the gene department!

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