Indoor Mold Exposure and Childhood Wheezing

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I’ve written before on the topic of indoor mold and while the issue has received lots of attention in the press, there hasn’t been much good science published on it.  There still isn’t a ton of great data out there, but this month’s Annals of Allergy, Asthma, and Immunology does have an interesting article looking at early childhood mold exposure and risk of developing asthma.

As with most published studies, the devil is in the details.  Whenever I read an asthma study, one of the most important questions I ask myself is how did the authors define asthma.  In many studies, patients are defined as asthmatic based on parental report or prior physician diagnosis.  I consider these to be weak definitions because they are so subjective.  The recent Annals study, however, used what I consider to be the best criteria: bronchodilator reversibility or methacholine challenge, which are the gold standard in asthma diagnosis.

Next, I wanted to know how the authors assessed for the presence of mold in homes.  For the uninitiated, such details are always contained in a section of an article called “Methods”.  Digression- If you’re in a hurry and you just want the quick and dirty info, many docs, including yours truly, will often read the abstract then skim the results and discussion.  But to truly understand an article you have to read the methods section.  It often contains phrases like this one from our aforementioned Annals study, “A Bayesian change-point analysis was applied to the logit of predicted values from a nonlinear regression of asthma on the ERMI.” I have no earthly idea what that means and I’d venture that most of the authors don’t either.  That’s why we hire statisticians to help us use the proper statistical techniques.

The methods section of this article contained a couple of interesting, and perhaps mildly humorous, points.  First, “an indoor visual and olfactory observation of the house conditions was conducted for the presence of carpets and evidence of mold.”  That’s a very sciency sounding way of saying they went looking and smelling for mold.  They did, however, perform a quantitative analysis by sampling house dust and performing an ERMI.  What’s an ERMI, you ask?  That stands for Environmental Relative Moldiness Index.  I think using the words “relative moldiness” in a scientific measure is hilarious.  They should try to make it more formal sounding.  Anyway, I was unfamiliar with the ERMI so I looked it up and it does seem to have some validity- it basically uses PCR to quantify mold spores levels in a sample of house dust.

So what did the study find?  Well the blurb you’ll see is that kids from a high ERMI home at 1 year of age were 2.6 times as likely to have asthma at age 7.  Interestingly, there was no correlation to allergic sensitization to mold, however.  So, either molds increase the development of asthma via a non-allergic mechanism, they needed to test for more kinds of mold, or there is some other confounding factor that goes along with a high ERMI level, like dust mites, for instance.  Cigarette smoking in the home also raised the risk of asthma at age 7.  The use of home dehumidifiers, presence of carpeting, age of home, and the categorization of home moldiness based on visual inspection did not correlate with asthma at age 7.

Overall, this is a well done study that raises good questions and sets the stage for further research into this area

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