To investigate if chronic mucus hypersecretion (CMH) can be used as a marker of asthma in young adults.

Cross-sectional study of a population sample of young Danish adults (n=624, 279 males), aged 19–29 years. Case history, including tobacco exposure and respiratory symptoms, was obtained by questionnaire. Pulmonary function, histamine responsiveness, bronchodilator reversibility, skin test reactivity, and leukocyte count were measured using standard techniques.

The overall prevalence of CMH was 7.7%, 8.4% in females and 6.9% in males, respectively, of whom more than 70% were current smokers. The presence of CMH was significantly associated with self-reported asthma, dyspnea at exertion, number of pack-years, lower FEV₁/FVC ratio, and lower BMI. However, no significant association was found between CMH and the following asthma-related factors: airway responsiveness to inhaled histamine, bronchodilator reversibility, self-reported rhinitis or eczema, atopy, FEV₁ (%pred), and B-eosinophil count.

CMH is a common finding in young adults, primarily in smokers. CMH was related to respiratory symptoms suggesting asthma, but no significant association was observed between CMH and objective signs of asthmatic airway lability. The present findings therefore may suggest that CMH is likely to be an early marker of smoking-related lung disease in young adults, instead of a marker of reversible obstructive lung disease, which may have important implications for the approach to young people presenting with respiratory symptoms suggesting asthma.