Overweight exacerbates air pollution symptoms in childhood asthma

By Helen Albert, Senior medwireNews Reporter

Children with asthma who are overweight are more likely to experience symptoms after exposure to indoor air pollution than normal-weight asthmatic children, show study findings.

Elizabeth Matsui (Johns Hopkins Hospital, Baltimore, Maryland, USA) and colleagues recruited 148 children with persistent asthma, aged 5-17 years, to assess the influence of weight on the effects of indoor exposure to nitrogen dioxide (NO₂) and fine particulate matter measuring less than 2.5 mm in diameter (PM_2.5) on a range of asthma symptoms.

The children all lived in an urban environment and were from minority groups (91% African-American). Based on body mass percentiles for age and gender, 4% of the children were underweight, 52% were normal weight, 16% were overweight, and 28% obese.

The team tested the amount of NO₂ and PM_2.5 present in the air in the children's bedrooms over a 5-7-day period and monitored asthma symptoms (days of slowed activity, days of wheezing, coughing or chest tightness when running or going upstairs, and nights of waking with asthma symptoms in the previous 2 weeks) at 3, 6, 9, and 12 months.

Overweight and obese children had significantly more asthma symptoms associated with exposure to PM_2.5 and NO₂ than normal-weight children. For example, children in these categories had approximately 0.7 more days of exercise-related symptoms and 0.6 more nights waking with asthma symptoms in the previous 2 weeks than normal-weight children with asthma.

Fewer symptoms were associated with NO₂ than PM_2.5 among overweight and obese participants, although some associations were seen. For example, each 10-fold increase in indoor NO₂ levels was associated with a 2.6- to 4.5-fold increase in risk for nocturnal symptoms of asthma among overweight and obese compared with normal-weight children.

"Children and adolescents with asthma in communities with a high prevalence of overweight status and indoor pollutant exposure might have greater asthma morbidity because of the interaction between these two factors," write Matsui et al in the Journal of Allergy and Clinical Immunology.

"These findings suggest that weight loss might reduce symptom responses to these indoor pollutants and that overweight and obese children and adolescents might benefit from indoor pollutant reduction to a greater extent than normal-weight children and adolescents," they conclude.

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