Background: In 1985 we became aware that the smoking of parents aggravates their children's asthma. Since then we have advised all referring doctors to urge parents not to expose their asthmatic children to smoke.
Methods: We investigated 807 nonsmoking asthmatic children, from 1 through 17 years of age, who were consecutively referred between 1983 and 1990. We compared the children who were seen before July 1986 with those seen after that date.
Results: Those seen in the later period had intimate exposure to a far smaller number of cigarettes smoked per day, both by mothers (7 vs 3, p = 0.005) and by fathers (5 2, p = 0.001). A concurrent improvement was observed in adjusted measures of asthma severity in their children (asthma score 7.5 vs 6.5, p = 0.047; forced expiratory volume in 1 second as a percent of predicted [FEV1%] 79.2 vs 93.7, p = 0.000; and forced expiratory flow rate during middle half of forced vital capacity [FEF25%-75%] 67.3 vs 82.0, p = 0.009), and for every cigarette less smoked in the room with the child the FEV1 increased by 3%. When parents of those seen in the later period were asked whether they had been told that smoke would aggravate their child's asthma, 80% affirmed that they had. The difference in asthma severity between the two time periods was much less in children of nonsmokers than in children of smokers.
Conclusion: It appears that if parents are aware that smoke will aggravate their child's asthma, the child will be exposed to fewer cigarettes, and the asthma will be less severe.