Key Point:

Obese children experience larger declines in lung function after exposure to air pollution than do normal-weight children.

ORLANDO, FLA—Although many of the adverse health effects associated with obesity in children are well known, a new one has just been added to the list: obese children have an increased susceptibility to air pollution.¹ This finding is especially important considering that the percentage of children and adolescents who are obese has risen dramatically, at least tripling in the past 25 to 30 years.

MORE PROBLEMS IN OBESE KIDS

In a recent study of 611 fourth and fifth graders, the obese children experienced more pronounced lung function declines in response to air pollution exposure than did the children who were of normal weight. Overall, the association between air pollution and decreased lung function was about two to five times stronger in the obese children, depending on the specific type of lung function measured, reported lead study author Heike Luttmann-Gibson, PhD, a research associate in environmental epidemiology at the Harvard School of Public Health in Boston.

Ten percent of Dr. Luttmann-Gibson’s cohort met the study definition of obesity—for boys, a body mass index (BMI) above 25.8 and for girls, a BMI greater than 24.8. During a three-month period, five indicators of the children’s lung function were measured while the children were at school: FVC, peak expiratory flow, FEV₁, forced expiratory volume in 0.75 seconds, and forced expiratory flow during the middle half of the FVC maneuver (FEF_25%-75%).

The measurements were then compared with the level of air pollution at school on the day before the lung function testing was performed. The analysis was adjusted for potentially confounding variables, such as age, sex, height, weight, asthma, maternal smoking during pregnancy, parental history of respiratory illness, and socioeconomic status.

In all of the children, lung function decreased as the level of air pollution increased. For example, for every 6.4-mg/m³ increase in the level of particulate matter with a diameter of less than 2.5 microns, FEF_25%-75% dropped by an overall mean of 2.8% and FEV₁ declined by 1.2%.

These changes were much greater in the obese children, however. For example, FEF_25%-75% decreased by an average of 5.2% in the obese children but fell by only 2.4% in the normal-weight children.

The analysis showed similar relationships between lung function and exposure to carbon monoxide and nitrogen dioxide (NO₂); both pollutants produced significantly larger reductions in mid-maximal expiratory flow (MMEF) in the obese children. “An increase in NO₂ of 9.7 parts per billion was associated with a decrease in MMEF of 2% in normal-weight children and of 12% in the obese children,” noted Dr. Luttmann-Gibson. Furthermore, the extent of the lung function decline in response to air pollution exposure was directly related to the degree of obesity.

OBESITY, AIR POLLUTION, AND INFLAMMATION

The findings of the present study are comparable to those of a previous investigation that assessed the long-term effects of air pollution on children who were followed from elementary school through high school. “We found that for long-term air pollution, the effects of exposure on lung function were also stronger in obese children,” related Dr. Luttmann-Gibson.

Elevated levels of inflammatory markers, such as interleukin-6, white blood cells, and C reactive protein, have been detected in blood samples from obese children and adults; this finding may explain the results of the two studies. “Since air pollution also leads to inflammation of the airways, we think there is a multiplier effect that makes obese children more sensitive to air pollution,” Dr. Luttmann-Gibson speculated.

—Timothy Begany

Reference
1. Luttmann-Gibson H, Dockery DW. Short-term effects of air pollution on lung function: Are obese children at higher risk? Paper presented at: annual meeting of the American Thoracic Society; May 23, 2004; Orlando.

Return to table of contents