Objective. Smoking among people who have asthma may be a serious health problem. We studied the prevalence of smoking and the relations between smoking and asthma, symptoms, medicine, and gender differences among adolescents with asthma.
Methods. A national cross-sectional study on health and lifestyles was performed in 1996–1997 using a computerized questionnaire in upper secondary schools in Denmark. We included 1887 pupils with asthma (defined as self-reported asthma diagnosed by a physician) and 20 688 controls. Smoking was categorized as daily, occasional, ex-smokers, and never smoked. We adjusted for age, gender, parents’ job and smoking, family type, body mass index, and exercise habits.
Results. In total, 37.7% smoked currently and 16.5% smoked daily; more girls than boys smoked. More pupils with asthma than without smoked daily (adjusted odds ratio [OR]: 1.15; 95% confidence interval [CI]: 1.04–1.33), they smoked significantly more cigarettes daily (10.3 vs 9.6), and more were heavy smokers (≥15 cigarettes daily; adjusted OR: 1.47; 95% CI:1.14–1.91). Furthermore, nearly twice as many pupils who had asthma with symptoms but were not using medicine smoked as pupils who had asthma without symptoms and were using medicine (adjusted OR: 1.84; 95% CI: 0.99–3.41). More boys with asthma than without started smoking before 14 years of age (adjusted OR: 1.75; 95% CI: 1.09–2.81). However, more pupils with asthma had tried to quit (adjusted OR: 1.26; 95% CI: 0.99–1.60). Pupils with and without asthma were occasional smokers and ex-smokers at a similar prevalence.
Conclusions. More pupils with asthma than without smoked daily, and they also smoked more cigarettes per day. This is a major health concern, as adolescents have a high smoking prevalence in Denmark.