Nonsmoker COPD represents a clinically Distinct Phenotype: A Prospective Observational Study

Chronic obstructive lung disease (COPD) has been characterized as a smoker's disease, which has resulted in the usual exclusion of never-smokers from COPD studies. It is now recognized that never-smokers account for nearly one-fourth of all COPD cases, and thus airflow limitation in never-smokers needs further evaluation. Our study aims to elucidate the clinical and physiological aspects of COPD in nonsmokers and to compare smokers and nonsmokers with COPD.

A total of 200 naïve sequential patients with COPD were recruited. The severity of airflow limitation in COPD patients was defined as per Global Initiative for COPD (GOLD) 2019 criteria, and the severity of breathlessness was assessed by the modified Medical Research Council (MRC) dyspnea scale. Data was collected using a patient pro forma, including risk factors for COPD and detailed clinical history. Phenotypic differences along with biomass exposure between never-smokers and smokers were analyzed.

Compared to smokers, never-smokers presented at a younger age (55.69 ± 11.5 years; p < 0.001), with a longer duration of dyspnea (5.05 ± 4.96 vs 7.35 ± 6.98 years, p < 0.01). Chest radiographs revealed hyperinflation in a higher number of smokers as compared to never-smokers (82.9 vs 64.6%, p < 0.05). On spirometry evaluation, smokers were found to have significantly poorer lung function [forced expiratory volume in first second (FEV1) 40.36 ± 17.76%; forced vital capacity (FVC): 58.16 ± 17.02%] as compared to never-smokers (FEV1: 47.1 ± 16.47%; FVC: 67.38 ± 17.02%) with p < 0.05. With respect to severity at presentation, most (45.8%) never-smokers presented with stage 2 COPD as compared to the majority of smokers (46.7%) who presented with stage 3 COPD (p-value of <0.05). Absolute eosinophil count (AEC) and eosinophil proportion in total leucocyte count (TLC) was significantly higher in never-smokers as compared to the smokers (232 ± 204.2 vs 309 ± 238.8, p < 0.05). Risk factor analysis showed mean biomass exposure index was significantly higher in never-smokers as compared to smokers (56.02 vs 6.28; p-value of <0.001).

Compared to smokers, COPD in never-smokers presents at a younger age, with a longer duration of dyspnea and higher eosinophil count. Biomass exposure is one of the major contributors to etiologies for COPD in nonsmokers.