Does passive smoking increase the frequency of health service contacts in children with asthma?

Background-Passive smoking is a major cause of respiratory morbidity in chi ldren. However, few studies give accurate estimates of the health effects o f passive smoking in children with asthma using an objective measure of exp osure. The effects of passive smoking using salivary cotinine levels to mea sure exposure were investigated. Methods-A sample of 438 children aged 2-12 years with asthma who had a pare nt who smoked were recruited in Tayside and Fife, Scotland. Health service contacts for asthma, assessed from GP case records, were used as a proxy fo r morbidity. Results-A weak U-shaped relationship was found between the salivary cotinin e level and health service contacts for asthma: compared with low cotinine levels those with moderate cotinine levels had a reduced contact rate (rela tive rate (RR) = 0.91, 95% confidence interval (CI) 0.80 to 1.05), whereas high cotinine levels were associated with an increased rate of contact (RR = 1.19, 95% CI 1.05 to 1.37). In contrast, a strong association was seen wi th the amount the parent reported smoking in front of the child: the higher the level the fewer visits were made for asthma (RR for everyday exposure = 0.66, 95% CI 0.56 to 0.77). This effect was not seen for non-respiratory visits. Demographic factors, age of child, and number of children in the fa mily all had a powerful effect on the number of visits for asthma. The pare nts' perception of asthma severity was associated with visit frequency inde pendent of actual severity (derived from drug treatment). Conclusion-High levels of parental smoking in the home are associated with a reduction in health care contacts for asthma. This could be due to a lack of awareness of asthma symptoms among heavy smokers or a reluctance to vis it the GP. Children with asthma who have parents who smoke heavily may not be receiving adequate management.