[Day care centers, infections and asthma].
Our objective was to use a causal model for childhood asthma to determine whether the effect of day care attendance on asthma was mediated by recurrent respiratory tract infections. The study is based on a cross-sectional survey among 1,447 children aged 6-16 years in Oslo. Their parents completed written questionnaires. A recursive logit model was used to estimate direct effects in terms of adjusted odds ratios (aOR). Year of birth, number of siblings and length of maternal education were significantly associated with after-school care attendance. Attendance increased the risk of early infections, aOR = 1.8 (1.3-2.5), and infections were associated with asthma, aOR = 4.9 (3.4-7.3). The crude association between after-school care and asthma was cOR = 1.5 (1.0-2.2), whereas the estimated direct effect was small and non-significant, aOR = 1.2 (0.8-1.9). The results may be influenced by over-reporting of infections among parents with children with asthma. Our results suggest that children who attend day care have an increased risk of asthma, with early infections as a mediator of risk.