Trends in wheeze in Dutch school children and the role of medication use

BACKGROUND: While the prevalence of childhood wheeze continues to increase in many countries, decreasing trends have also been reported. This may be explained by increased use of asthma medication, which effectively suppresses wheeze symptoms. In this study we investigated trends in wheeze in Dutch school children between 1989 and 2005, and their association with medication use. METHODS: In five repeated cross-sectional surveys between 1989 and 2005, parents of all 5- to 6-year-old and 8- to 11-year-old children eligible for a routine physical examination were asked to complete a questionnaire on their child's respiratory health. We identified all children for whom a questionnaire was completed in two successive surveys. Children were grouped according to birth year and classified into one out of four wheeze categories: "no wheeze," "discontinued wheeze," "continued wheeze," or "new-onset wheeze." RESULTS: In total, 3,339 children, born in 1983 (N = 670), 1988 (N = 607), 1992 (N = 980), and 1995 (N = 1,082), participated twice. Over the study period, the proportion of children with "no wheeze" increased from 73.8% to 86.1% (Ptrend < 0.001), while the proportion of children with "discontinued" and "continued" wheeze decreased from 13.2% to 6.3% (Ptrend < 0.001) and from 8.8% to 3.1% (Ptrend < 0.001), respectively. Medication use was consistently associated only with the presence of wheeze symptoms and this association did not change over time (Pbirth year × medication use > 0.05 for all wheeze categories). CONCLUSION: An increasing trend of Dutch school children with "no wheeze," and decreasing trends of children with "discontinued" and "continued" wheeze between 1989 and 2005 could not be explained by (increased) medication use. This suggests that wheeze prevalence is not masked by medication use, but is truly declining.