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Study supports pollution link to asthma in childhood

By jeremyc | March 12, 2010

Source: MedWire News

Exposure to increased levels of air pollution in early childhood is associated with an increased risk for asthma and related symptoms at the age of 8 years, research shows.

“Exposure to ambient air pollution can exacerbate existing asthma,” explain Ulrike Gehring (Utrecht University, The Netherlands) and team. “The role of exposure to ambient air pollution in the development of childhood asthma, allergy, and related symptoms, however, remains less clear.”

To investigate further, the researchers assessed data on 3863 children who participated in the Dutch Prevention and Incidence of Asthma and Mite Allergy (PIAMA) study.

Annual parental questionnaires were used to record the occurrence of asthma and related symptoms, such as wheeze, among the children during the first 8 years of life. Subgroups of 1700 and 936 children also underwent allergic sensitization and bronchial hyper-responsiveness assessments, respectively, at the age of 8 years.

Concentrations of nitrogen dioxide (NO2), particulate matter measuring less than 2.5 µm in diameter (PM2.5), and “soot” were assessed at each child’s birth address over four 2-week periods in 1 year, and land-use regression models were used to calculate long-term average concentrations.

The researchers found that the annual prevalence of asthma was 3–6% and the annual prevalence of the asthma-like symptoms was 12–23%.

After accounting for factors such as gender, family history of allergies, breastfeeding, parental smoking habits, day-care attendance, and signs of dampness in the home, the researchers found that an interquartile range increase in annual PM2.5 levels (3.2 µg/m3) was associated with a significant increase in both the incidence and prevalence of asthma, at odds ratios (ORs) of 1.28 and 1.26, respectively. Such an increase was also associated with a significant rise in the prevalence of asthma-related symptoms, at an OR of 1.15.

Similar increases in the incidence and prevalence of asthma and asthma-related symptoms were found for interquartile range increases in annual levels of NO2 and soot.

These associations were stronger among children who had remained in the same house since birth than in those who had moved during the study period, the researchers note in the American Journal of Respiratory and Critical Care Medicine.

Increases in PM2.5, NO2, and soot levels were not associated with an increased risk for bronchial hyper-responsiveness and allergic sensitization, however.

Gehring and team conclude that “exposure to traffic-related air pollution may cause asthma in children monitored from birth to 8 years of age.”

Topics: | Asthma |

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