What are the Differences Between Smoker and Non-smoker COPD Cases? Is it a Different Phenotype?

Objective: The most important risk factor for chronic obstructive pulmonary disease (COPD) is smoking. However, more than 25% of patients do not have a history of smoking. The intent of this study is to identify characteristics of COPD patients that are non-smokers.

Material and methods: The records of patients with COPD were retrospectively reviewed. Smoking history, comorbidities, exacerbations, biomass, and environmental tobacco smoke (ETS) exposures were identified. Also, age, gender, pulmonary function test (PFT) values, modified Medical Research Council (mMRC) dyspnea scores were recorded. Non-smokers exposed to any of the COPD risk factors above were grouped and the data were analyzed to determine the specific characteristics of COPD that applied to them.

Results: A total of 706 COPD patients were analyzed with a mean age of 67.2 ± 9.4. Of these patients, 93 (13.2%) were female and 613 (86.8%) were male. Of the 706 patients, 128 (18.1%) were non-smokers. The percentage of male patients having COPD was significantly lower in the non-smoker group (P < .001). However, biomass, ETS exposure in childhood, and a history of previous respiratory infection were significantly higher in the non-smoker group (P < .001). The mean body mass index (BMI) was greater in non-smokers than smokers.

Conclusion: Non-smokers with COPD have more biomass, ETS exposure, and infection history in childhood. They also have less impairment of airflow limitation, better symptom scores, and greater BMIs. Smoking history can be used to determine a different phenotype.