TY - JOUR T1 - Changes in smoking habits and risk of asthma: a longitudinal population based study JF - European Respiratory Journal JO - Eur Respir J SP - 549 LP - 554 DO - 10.1183/09031936.01.00100801 VL - 18 IS - 3 AU - N.S. Godtfredsen AU - P. Lange AU - E. Prescott AU - M. Osler AU - J. Vestbo Y1 - 2001/09/01 UR - http://erj.ersjournals.com/content/18/3/549.abstract N2 - A common statement from exsmokers is that symptoms of asthma develop shortly after smoking cessation. This study, therefore, investigated the relationship between smoking cessation and development of asthma in a large cohort from the Copenhagen City Heart Study (CCHS).The CCHS is a longitudinal, epidemiological study of the general population from the capital of Denmark, conducted between 1976 and 1994. The study population involved the 10,200 subjects who provided information on self-reported asthma and smoking habits from the first two examinations (baseline and 5-yr follow-up), and the 6,814 subjects who also attended the third and last examination (10-yr follow-up). The point-prevalence of smoking cessation as well as the asthma incidence between examinations was estimated, and a multivariate logistic regression model was used to examine the relationship between changes in smoking habits and development of asthma.During the study period, asthma incidence increased from 1.2–4.2%. Between examinations 1,316 subjects quit smoking. Smoking cessation between examinations was significantly related to reported asthma at follow-up. With never-smokers as the reference group and following adjustment for sex, age, chronic bronchitis, level of forced expiratory volume in one second and pack-yrs of smoking, the odds ratio (OR) for developing asthma when quitting smoking between examinations was 3.9 (95% confidence interval (CI) 1.8–8.2) from baseline to first follow-up and 3.1 (95% CI 1.9–5.1) from first to second follow-up. Continuing smoking also increased the risk of asthma significantly (OR 2.6 and 2.0, respectively).The results indicate that exsmokers have a higher incidence of self-reported asthma than never-smokers. It is likely that subjects perceive chronic obstructive pulmonary disease as asthma, hence the relationship between smoking cessation and asthma might be due to misclassification rather than causality.This study was supported by grants from the Danish Epidemiology Science Centre, the Danish Ministry of Health, the Health Insurance Fund, the Danish Lung Association, the Danish Heart Foundation, the Danish Medical Research Council and the Else and Mogens Wedell-Wedellsborg Foundation. ER -