Involuntary Smoking and Asthma Severity in Children: Data from the Third National Health and Nutrition Examination Survey

Mannino DM, Homa JM, Redd SC. Chest. 2002;122: 409–415 Purpose of the Study. To determine the indicators of asthma severity among children in the United States with high and low levels of tobacco exposure. Study Population. The subjects were 523 children (age: 4–16) with physician-diagnosed asthma. Methods. The study population was obtained from the Third National Health and Nutrition Examination Survey (NHANES III), which is a Centers for Disease and Prevention (CDC)-sponsored survey of a representative US population that underwent an extensive evaluation including a questionnaire, physical examination, lung function, and serum cotinine levels. Only children with a prior diagnosis of asthma were included in the analysis. Asthma severity was based on the frequency of symptoms. Serum cotinine levels were ranked as low ( 0.115 ng/mL), intermediate (0.116–0.639 ng/mL), and high (0.64–0.20 ng/ml). Subjects that reported active smoking or had serum cotinine 20 ng/mL (indicating active smoking or use of chewing tobacco) were excluded. Cotinine levels were then compared with measures of asthma severity. Results. Of the 13 944 children 17 years old who participated in NHANES III, 1025 had physician-diagnosed asthma. After exclusion for children 4 years old, those without physical examinations or cotinine levels and 13 with cotinine levels 20 523 children remained in the study group. Of these, 294 completed pulmonary function testing. Of the 523 tobacco-exposed children studied, 78.6% had mild asthma, 6.8% had moderate asthma, and 14.6% had severe asthma. The authors found that increased asthma severity was associated with higher cotinine levels. They also found that lower forced expiratory volume in 1 second (FEV1) levels and a greater proportion of children with FEV1 80% were also associated with increased levels of cotinine. They found a mean FEV1 decrement of 8.1% in the environmental tobacco smoke (ETS)-exposed children versus 1.8% in all the children. A surprising finding was that children with higher cotinine levels were less likely to have been hospitalized for asthma in the previous year, but all other measures of severity were higher in the group. Conclusions. The authors conclude that their study provides evidence that children with asthma who are exposed to tobacco smoke have generally increased asthma severity and decreased lung function. Reviewer’s Comments. Yet another study to provide evidence to our patients and their caregivers that tobacco smoke is detrimental to health, specifically in this study to children with asthma.