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Abstracts: ISEE 20th Annual Conference, Pasadena, California, October 12–16, 2008: Contributed Abstracts

Association of Childhood Asthma with School Commuting Time

Liu, F*; McConnell, R*; Wu, J

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doi: 10.1097/01.ede.0000340550.23965.d8
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ISEE-1585

Background:

Several previous studies indicate that living near major roadways increases risk of asthma, but the association between risk of asthma and the exposure to on-road commuting exposure to air pollution has not been explored.

Methods:

We used time and distance from school to home as an indicator of commuting exposure in a cohort of 4737 kindergarten and first grade children participating in the southern California Children’s Health Study. Time and distance from school to home was obtained by using a PERL program employing the routines of MAPQUEST. We examined the relationships between prevalent asthma, lifetime asthma, late onset asthma [diagnosed age 5 or later], early [before age 4] and late onset wheeze [age 4 or later], and commuting time at the time of study entry in 2003.

Results:

Compared with children in the lower quartile of commuting time, those in the upper quartile were more likely to have lifetime asthma (OR 1.31; 95%CI 1.01–1.71), prevalent asthma (OR 1.29; 95%CI 0.98–1.70), late onset asthma (OR 1.94; 95%CI 1.01–3.74), and late onset wheeze (OR 1.44; 95%CI 1.00–2.10), but not early onset wheeze or asthma. These associations were robust to confounding by socio-demographic and household characteristics and by traffic-related exposure modeled at the home of the child (which was independently associated with asthma). Similar associations were obtained between asthma and commuting distance to school.

Conclusions:

These results suggest that commuting may increase the risk of asthma. However, the latency from entry to school was short, range of commuting time was modest (upper quartile range from 5 to 44 minutes) and exposure would have been misclassified by this crude index. (Information about actual commuting route, other on-road travel, and traffic volume was not available). Therefore, it is possible that (1) these results could be explained by other unmeasured confounders, (2) school commuting time may have been a proxy for on-road travel elsewhere, or (3) effects of even modest on-road exposure were substantial.

© 2008 Lippincott Williams & Wilkins, Inc.