Occup Environ Med 61:475 doi:10.1136/oem.2003.011205
  • Letter

Asthma and swimming pools: statistical issues

  1. B Armstrong1,
  2. D Strachan2
  1. 1Public and Environmental Health Unit, London School of Hygiene and Tropical Medicine, Keppel St, London WC1E 7HT, UK;
  2. 2Department of Public Health Sciences, St George’s Hospital Medical School, Cranmer Terrace, London SW17 0RE, UK

      Bernard and colleagues1 presented results from several studies investigating childhood asthma in relation to swimming pool use. Though the studies were generally well conducted, there are some respects in which the statistical analysis and interpretation are misleading.

      The study of asthma prevalence in relation to swimming pool use was essentially an ecologic design—the unit of analysis was the school. Though the study of correlations between asthma prevalence and indexes …