Background and objectives Chronic obstructive pulmonary disease (COPD) mainly develops after long-term exposure to cigarette or biomass fuel smoke, but also occurs in non-smokers with or without a history of asthma. We investigated the proportion and clinical characteristics of non-smokers among middle-aged to elderly subjects with airflow obstruction. Methods We retrospectively analyzed 1,892 subjects aged 40–89 years who underwent routine preoperative spirometry at a tertiary university hospital in Japan. Airflow obstruction was defined as a forced expiratory volume in 1 second (FEV 1 )/forced vital capacity < 0.7 or as the lower limit of the normal. Results Among 323 patients presenting with FEV 1 /forced vital capacity < 0.7, 43 had asthma and 280 did not. Among the non-asthmatic patients with airflow obstruction, 94 (34%) were nonsmokers. A larger number of women than men with airflow obstruction had asthma (26% vs. 7.6%, p < 0.001), or were non-smokers among non-asthmatics (72% vs. 20%, p < 0.001). Non-asthmatic non-smokers, rather than non-asthmatic smokers, asthmatic non-smokers, and asthmatic smokers, exhibited better pulmonary function (median FEV 1 : 79% of predicted FEV 1 vs. 73%, 69%, and 66%, respectively, p = 0.005) and less dyspnea on exertion (1% vs. 12%, 12%, and 28%, respectively, p = 0.001). Pulmonary emphysema on thoracic computed tomography was less common in non-smokers (p < 0.001). Using the lower limit of the normal to define airflow obstruction yielded similar results. Conclusions There are a substantial number of non-smokers with airflow obstruction compatible with COPD in Japan. In this study, airflow obstruction in non-smokers was more common in women and likelier to result in mild functional and pathological abnormalities than in smokers. Further studies are warranted to investigate the long-term prognosis and appropriate management of this population in developed countries, especially in women.
Takiguchi, H., Takeuchi, T., Niimi, K., Tomomatsu, H., Tomomatsu, K., Hayama, N., … Asano, K. (2018). Proportion and clinical characteristics of non-asthmatic non-smokers among adults with airflow obstruction. PLoS ONE, 13(5). https://doi.org/10.1371/journal.pone.0196132