Local road traffic activity and the prevalence, severity, and persistence of wheeze in school children: combined cross sectional and longitudinal study

Objectives-To investigate the relation between local road traffic activity and the occurrence, severity, and persistence of wheeze in children. Methods-Data on wheeze and asthma were collected in a cross sectional quest ionnaire survey of 22 968 primary school children (age 4-11) and 27 826 sec ondary school children (age 11-16) in the Nottingham area. Direct measures of road traffic flow were made in the locality of each school and combined with Local Authority traffic data for major roads to estimate local traffic activity in vehicle metres/day/km(2). Assessment of the effects of potenti al confounders was performed in nested case-control groups of 6576 primary and 5936 secondary children. Data on frequency of wheeze were collected for the cases to study disease severity. Longitudinal data on a historical coh ort of 883 children who reported wheeze when aged 4-11 in 1988 were used to study the persistence of wheeze into adolescence. Results-Unadjusted prevalence of wheeze in the past year within schools var ied widely but was not associated with traffic activity in the school local ity (weighted regression coefficient beta=-0.01, p=0.93 for primary schools , beta=-0.18, p=0.26 for secondary schools). The risk of wheeze in individu al primary school children was not associated with traffic activity analyse d as a continuous variable, although there was some suggestion of a weak, n on-linear plateau effect. Similar effects were found for diagnosed asthma a nd recent cough. There was no evidence of any relation between traffic acti vity and risk of wheeze in secondary school children. There were positive b ut non-significant dose related effects of traffic activity on wheeze sever ity in primary and secondary children and on persistence of wheeze in the l ongitudinal cohort. Conclusions-Traffic activity in the school locality is not a major determin ant of wheeze in children.