Effect of Cumulative Tobacco Exposure on Blood Eosinophil Level in Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is a lung condition characterized by persistent airway obstruction and is associated with various phenotypes and endotypes. While eosinophilic inflammation is typically seen in asthma, it also occurs in COPD, with known increases in eosinophil counts during exacerbations. However, the impact of cumulative tobacco exposure on eosinophil counts is not well understood. This study aims to investigate this relationship. Data for this prospective study were collected from three centers, involving patients diagnosed with COPD. Patients' demographic data and eosinophil levels were documented. They were categorized according to GOLD Stages A, B, and E, and each group was analyzed relative to the amount of cigarette smoking. The study enrolled 227 COPD patients, predominantly male (92.5%) with an average age of 64.6 years. Of the study population, 39.8% (<i>n</i>: 90) were current smokers, and 86.9% had a smoking history of more than 20 packs/year. The average smoking history of our patients was 52.38 ± 30.69 (mean ± SD) pack/year. Our patients had an average smoking history of 39.49 ± 12.56 years. No statistically significant results were found between the amount of cigarettes smoked and eosinophil counts. However, in the correlation between smoking history and eosinophil counts, higher eosinophil counts were found in those who had former smoking compared to current smokers or never smokers. While the number of pack-years and the duration of smoking increased from Stage A to Stage E, daily cigarette consumption remained constant, and eosinophil counts did not show a significant correlation with the quantity of tobacco. Eosinophil counts in COPD patients did not vary significantly with either the amount of tobacco exposure or the severity of COPD as categorized by GOLD stages. These findings suggest that factors other than tobacco exposure may influence eosinophil levels in COPD patients.