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Background: The overlap between asthma and chronic obstructive pulmonary disease (COPD) is an important clinical phenomenon. However, the prevalence of asthma-COPD overlap syndrome (ACOS) is not known. Aims: To investigate the prevalence of ACOS among asthmatic patients with a smoking history, and evaluate the factors predicting ACOS in this patient group. Methods: We investigated 190 primary care asthma patients with no previous diagnosis of COPD, but who were either current or ex-smokers, with a smoking history of at least 10 pack-years. Spirometry was performed on all the patients while they were taking their normal asthma medication. Patients were considered to have ACOS if their postbronchodilator forced expiratory volume in 1 s/forced vital capacity was <0.70.Results:Fifty-two (27.4%) of the patients were found to have ACOS. Age ≥ 3/460 years and smoking for ≥ 3/420 pack-years were the best predictors of ACOS. If both of these criteria were met, the odds ratio (95% confidence interval) for ACOS was 6.08 (2.11-17.49), compared with the situation where neither of these criteria were fulfilled. Conclusions: There is a high prevalence of ACOS among primary health care asthmatics with a positive smoking history but no previous diagnosis of COPD. In this population, age over 60 years and a smoking history of more than 20 pack-years were the best predictors of ACOS.
Kiljander, T., Helin, T., Venho, K., Jaakkola, A., & Lehtimäki, L. (2015). Prevalence of asthma-COPD overlap syndrome among primary care asthmatics with a smoking history: A cross-sectional study. Npj Primary Care Respiratory Medicine, 25. https://doi.org/10.1038/npjpcrm.2015.47