Another Childhood Obesity Villain – Breathing

Smoke PlumeThese words are from Dr. Frederica Perera of Columbia University, a winner of the prestigious Heinz Award from the Heinz Family Foundation:

Exposure to endocrine disruptors in the air can alter the normal hormonal signaling and affect growth and development, so there is a tendency for some children to become more obese. We are concerned about pre-natal exposures because they can cause greater absorption and retention of toxics in the developing child. Because such children have immature biological defenses against exposures, chronic diseases that affect someone later in life can be seeded.

This was the result of a public health study to which the Columbia University environmental health researcher had devoted 10 years. Previous research had linked air pollution with low birth weight, infant mortality, asthma and other respiratory illnesses, slow brain development, and allergies. Dr. Perera, having studied 720 mothers and their children for a decade, added childhood obesity to this list.

At the end of last year, Environmental Health Perspectives published a study from the Keck School of Medicine at the University of Southern California, which pointed an accusatory finger at the combination of air pollution from motorized vehicles and secondhand cigarette smoke. There had been other studies indicating that secondhand smoke could be a childhood obesity villain, and others that suggested roadway pollution was also to blame. This one looked at the combined effects, reporting all the complicated details of how much each factor influenced the subjects.

The research included 3,318 children who were part of the Southern California Children’s Health Study and whose Body Mass Index numbers were measured annually over 8 years. It highlighted the combinatory effect of the two harmful influences. The word synergy expresses the idea that the whole can be more than the sum of its parts, and a synergistic effect is what the researchers found. Journalist Ryan White says the study found:

Exposure to high levels of roadway pollution alone was associated with average increases of 0.80 BMI units…while children with secondhand smoke exposure and low roadway pollution averaged 0.85 higher.. But when investigators looked at children with high exposures to both tobacco smoke and air pollution, their BMIs were on average 2.15 higher over eight years.

Adding 0.80 to 0.85 gives your 1.65, not 2.15, and that’s what synergy is all about. Another academic term put to use here is “confounder,” which is a factor that would skew the results. But this study meticulously weeded out confounders—a large number of them, including socio-economic status, population density, the child’s participation in sports, the child’s history of asthma, the “walkability” of the child’s neighborhood and the availability of recreational facilities, and many other factors. Although the scientists do not fully understand why the combination of roadway pollution and secondhand smoke should have such an emphatic effect, they believe the results are clear.

Your responses and feedback are welcome!

Source: “Decade-long study wins Heinz Award after findings include link between air pollution, obesity.” post-gazette.com, 05/18/15
Source: “Combo of tobacco smoke, road pollution tied to childhood obesity,” CenterForHealthJournalism.org, 12/03/14
Image by William Warby

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