The effect of ozone on inner-city children with asthma - Identification ofsusceptible subgroups

Within a cohort of 846 inner-city asthmatic children aged 4 to 9 yr, we loo ked for subgroups that were more susceptible to the effects of summer ozone . Daily diaries were compared with ambient ozone levels to evaluate effect modification by demographic and environmental characteristics. Children bor n > 3 wk prematurely or weighing < 5.5 Ib. had greater declines in morning % peak expiratory flow rate (PEFR) (1.8% versus 0.3% per 15 ppb ozone, p < 0.05) and a higher incidence of morning symptoms (odds ratio = 1.42 versus 1.09 per 15 ppb ozone, p < 0.05) than did children who had been full-term i nfants of normal birthweight. Among children who had been of low birthweigh t (LBW) or had been premature infants, greater declines were seen among tho se whose reported baseline medication category was "no medication" (3.2% de cline) or "steroids" (2.7%) as opposed to beta agonists or xanthines (0.8%) or cromolyn without steroids (0.1%). Among the children who had been norma l birthweight and full-term infants, the cromolyn without steroids group ha d the greatest declines in %PEFR (1.3%, versus < 0.5% in each of the other three groups). Nonatopic children also had greater responses to ozone. We c onclude that among an asthmatic cohort, children who had had an LBW or a pr emature birth showed the greatest responses to ozone.