Cough and sleep in inner-city children.

This study aimed to determine whether cough at night keeps children awake, to describe the relationship between children's cough and sleep and to report parents' perceptions of their children's cough and sleep. Thirty-nine children with reported persistent cough at night (>3 weeks) were recruited and studied for 6 nights by video-recording. Coughs were counted and sleep state was coded for awake, restless sleep and quiet sleep. The relationships between cough and sleep state between subjects and within subjects were examined by correlation and regression. After night 2 the parents were asked whether their child had coughed or had disturbed sleep and after night 6 they were asked whether there had been any change. There was a weak relationship between log percentage of the night awake and log number of coughs (r=0.13, SE 0.036), and log (percentage of the night awake plus restless sleep) and log number of coughs (r=0.016, SE 0.0071). If the relationship between cough and sleep state is causal, halving the number of coughs will reduce the percentage of the night awake by 9% (95% confidence interval (CI) 4-15%) and percentage awake and restless by 1% (95% CI 0-2%). All but one parent correctly identified coughing and 82% detected change. Most could not comment on their child's sleep. Improvement in cough would result in little reduction in either the percentage of the night awake or awake and restless in the average child in the population studied. Parents could detect whether their children were coughing but not whether their sleep was disturbed.