Cumulative effect of smoking on disease burden and multimorbidity in adult-onset asthma

Smokers and patients with heavy smoking history have usually been excluded from clinical studies of asthma. Thus, little is known about the impact of lifelong, cumulative tobacco exposure on asthma [1, 2]. The effect of smoking status (never-, ex- or current smoker) on disease burden of asthma has been more commonly recognised, but the impact of smoking history in pack-years has rarely been evaluated [3–6]. The impact of smoked pack-years has been previously reported only by few studies, showing adverse effects on lung function and asthma control [5, 7–10], whereas no significant differences in healthcare use, asthma-related questionnaires or medication use were reported among ex-smokers with severe asthma when patients were categorised based on smoked pack-years [4]. Disease burden and multimorbidity in adult-onset asthma increase dose dependently with smoked pack-years <http://bit.ly/311627j> We are grateful to research nurse Aino Sepponen for her input with data management.