Chest
Volume 94, Issue 4, October 1988, Pages 701-708
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Passive Smoking and the Seasonal Difference of Severity of Asthma in Children

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To learn whether asthmatic children are affected by passive smoking, we studied 240 unselected consecutively referred asthmatic subjects, aged 7 to 17 years. To discover whether children of smokers are affected more severely during the cold, wet season, when windows are closed and children are indoors, than during the warm, dry season, when houses are well ventilated and children spend more time outdoors, we compared lung function tests recorded during the two seasons. If seen during the cold, wet season, children of smoking mothers compared with those of nonsmoking mothers had a lower FEV1% (74 vs 86, p = .00), FEF25-75 percent (56 vs 75, p = .00) and PC20 histamine (0.85 vs 1.95, p = .01). There was a highly significant correlation between the number of cigarettes the mother smoked in the house and each of these lung function test results, indicating a dose-response relationship. Those seen during the warm, dry season, by contrast, did not have lower mean spirometric test results if their mothers were smokers than if nonsmokers, and there was no correlation between the number of cigarettes the mother smoked in the house and the result of any lung function test. Our results strongly support the hypothesis that cigarette smoke from the mother aggravates her child's asthma. (Chest 1988; 94:701-08)

Section snippets

Population

The series included every child with asthma or a wheezy chest who was aged 7 to 17 years and had been referred to one of us (ABM) at the Children's Hospital in Vancouver.

There were 247 subjects. Of these, 160 were being seen for the first time, and 87 had been examined on a previous occasion; they were being reassessed at the request of their primary care physicians. For both new and old patients only the data recorded at the initial visit during the period Nov 1, 1983, to May 31, 1986, were

RESULTS

The two groups of children were comparable for the following features: age; male-female ratio; the duration of asthma; the occurrence, during the preceding two weeks, of a respiratory infection, a condition that may have influenced lung function test results; the taking of recent medication; and the percentage with a positive skin prick test to an inhalant allergen, an indication of atopy (Table 1). The two groups did differ, however, in the mean diameter of the wheal produced by a skin prick

DISCUSSION

The results suggest that passive smoking in the home worsens bronchial irritability and narrows the bronchi in asthmatic children. These changes were more marked in the children of mothers who smoked, compared with those of mothers who did not smoke, as reported in our previous study.17 The likelihood that it was passive smoking that caused the increased severity of asthma in the children of smokers, rather than some other difference between them and the children of nonsmokers, was strengthened

ACKNOWLEDGMENTS

The authors thank Mr. Ronnie Sizto for computer programming, Mrs. Janice Fuller, R.N., for interviewing patients, and Mrs. Huguette Brown for performing the tests.

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    Supported in part by a grant from the British Columbia Lung Association.

    Manuscript received November 13; revision accepted March 21.

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