Among obese, disadvantaged Latino children, greater exposure to air pollution was associated with an adverse effect on glucose homeostasis markers that reflect risk of type 2 diabetes, in a new study.
Specifically, in this study of children who were 8 to 15 at entry and followed for a mean of 3.5 years, exposure to higher levels of air pollution was linked with lower insulin sensitivity, a decline in beta-cell function, and a higher body mass index (BMI) at age 18 — independent of initial excess weight.
The study by Tanya L Alderete, PhD, University of Southern California (USC), Los Angeles, and colleagues was published online January 30 in Diabetes.
"It has been the conventional wisdom that [the current] increase in diabetes is the result of an uptick in obesity due to sedentary lifespans and calorie-dense diets," senior author Frank Gilliland, MD, from the Keck School of Medicine, USC, said in a statement. However, "our study shows air pollution also contributes to type 2 diabetes risk."
"Importantly," the adverse effects of air pollution on insulin homeostasis, insulin sensitivity, and beta-cell function were independent of adiposity, Dr Alderete and colleagues stress.
In fact, the effect of high levels of air pollution on these metabolic parameters was "similar and, in some cases, larger than those of a 5% increase in body fat."
Although the findings may not be generalizable to other populations, "this study supports an important role for [exposure to air pollution] in the etiology of type 2 diabetes in youth," the researchers conclude.
Air Pollution and Glucose Homeostasis
Previous studies have reported that ambient and traffic-related air pollution may contribute to the development of obesity and type 2 diabetes, Dr Alderete and colleagues note.
However, it was not known if long-term exposure to elevated levels of nitrogen dioxide and tiny (< 2.5-µm) particles of matter had an adverse effect on insulin sensitivity and beta-cell function in children at high risk of developing diabetes.
To investigate this, the researchers examined data from 314 Latino children who lived in Los Angeles, did not have diabetes, and were overweight or obese (BMI > 85th percentile) when they enrolled in the Air Study at the Childhood Obesity Research Center (CORC).
The children had a mean age of 11; 58% were boys, and 66% were in prepuberty or early puberty.
They had yearly physical exams and tests to determine glucose tolerance, insulin sensitivity, and beta-cell function (acute insulin response to glucose times insulin sensitivity).
The researchers also determined the children's socioeconomic status and estimated how much air pollution they had been exposed to each month in the prior year.
Higher exposure to ambient air pollution was associated with adverse effects on glucose homeostasis, after adjustment for sex, Tanner stage of puberty, season, socioeconomic status, percentage of body fat, and study entry year.
For example, at age 18, a 4-μg/m3 difference in long-term exposure to small air particles was associated with a 27% higher fasting insulin level (P = .01) and a 37% higher insulin level in the 2-hour oral glucose tolerance test (P = .007) — indicating less responsiveness to insulin.
And at age 18, chronic exposure to a 5-ppb higher nitrogen-oxide exposure was associated with 13% lower beta-cell function (P = .04).
Higher exposure to air pollution was also associated with a more rapid increase in BMI and central adiposity in these already-overweight or obese children.
"Poor air quality appears to be a catalyst for obesity and diabetes in children, but the conditions probably are forged via different pathways," corresponding author Michael Goran, PhD, from the Keck School of Medicine of USC, speculated.
Everyone Should Avoid Unnecessary Exposure to Air Pollution
The study indicates that adults should also try to minimize their exposure to air pollution, where possible, say the authors.
"It's important to consider the factors that you can control — for example, being aware that morning and evening commute times might not be the best time to go for a run," Dr Alderete observed.
"Change up your schedule so that you're not engaging in strenuous activity near sources of pollutants or during peak hours."
The authors have no relevant financial relationships.
Diabetes. Published online January 30, 2017. Abstract
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Cite this: Air Pollution 'a Catalyst' for Obesity, Diabetes in Children - Medscape - Feb 13, 2017.