The impact of pre- and post-natal smoke exposure on future asthma and bronchial hyper-responsiveness

Aim: To analyse the impact of pre‐ and post‐natal smoke exposure on asthma presence, bronchial hyper‐responsiveness, airway function and active smoking in early adulthood. Methods: We have prospectively studied 101 children hospitalized due to wheezing before the age of 2 years. The cohort was re‐investigated at age 17–20 years and tested for airway function and bronchial hyper‐responsiveness. Data on maternal smoking during pregnancy were obtained from the Swedish Medical Birth Register. Results: There was a significant, independent correlation between both pre‐ and post‐natal smoke exposure and asthma at age 17–20 years, OR 3.5 (1.1–11.3) and 3.4 (1.2–10.1), respectively. Maternal smoking during pregnancy was an independent risk factor for current bronchial hyper‐responsiveness, OR 6.6 (1.2–35.5). Pre‐natal smoke exposure seemed to negatively affect small airway function in early adulthood due to structural changes. Post‐natal smoke exposure was independently associated with an increased risk of current smoking, OR 7.4 (1.6–35.2). Conclusion: In subjects hospitalized due to early wheezing, pre‐ and post‐natal smoke exposure increase the risk of asthma in early adulthood. The connection between pre‐natal smoke exposure and asthma appears to be mediated via the development of bronchial hyper‐responsiveness. Smoke exposure in infancy is associated with an increased risk of active smoking in early adult age, which is in turn linked to current asthma.