Chronic productive cough in school children: prevalence and associations with asthma and environmental tobacco smoke exposure

Abstract

Background: The relationships between chronic productive cough (CPC), environmental tobacco smoke (ETS) exposure, and asthma are not clearly established in children. Therefore, we wished to determine the prevalence of CPC and examine the relationships between CPC, ETS exposure, and asthma in young teenagers.

Methods: We performed a cross sectional survey of 2397 Seattle middle school students, 11-15 years old, using written and video respiratory-symptom questionnaires. We defined CPC as--daily cough productive of phlegm for at least 3 months out of the year; current asthma as--yes to "Have you had wheezing or whistling in your chest in the past 12 months?" and yes in the past year to any of the four video wheezing/asthma video scenarios; and ETS exposure as exposed to tobacco smoke at least several hours each day. We used multilogistic regression to examine relationships between CPC, asthma, and ETS exposure and included in the model the potentially confounding variables race, gender, and allergic rhinitis.

Results: The prevalence of CPC was 7.2%. Forty-seven percent (82/173) of children with CPC met criteria for current asthma, while only 10% (214/2224) of those without CPC had current asthma. Current asthma had the strongest associated with CPC, odds ratio (OR) 6.4 [95% CI 4.5-9.0], and ETS was independently associated with both CPC, OR 2.7 [1.8-4.1] and asthma, OR 2.7 [1.5-4.7].

Conclusion: In a population of young teenagers, CPC was strongly associated with report of current asthma symptoms and also with ETS exposure. This suggests that asthma and ETS exposure may contribute to CPC in children. However, this study was not designed to determine whether asthma was the actual cause of CPC in this population of children.

Figure 1

The relationship between CPC and asthma. This Venn diagram depicts the relationship between chronic productive cough (CPC) and asthma. See text for definitions of the current, possible, and no asthma groups. While the criteria for these groups make them mutually exclusive, they are shown as overlapping to indicate that in reality there is crossover between the groups. The numbers in parentheses are the number of children with the condition, e.g. current asthma. The proportions of children in each group with CPC (28%, 9.5%, and 2.3% for the current asthma, possible asthma, and no asthma groups, respectively), were statistically significantly different, p < 0.001 for each comparison.