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Blood eosinophil counts and the development of obstructive lung disease: the Kangbuk Samsung Health Study
Hye Yun Park1,2, Yoosoo Chang3,4,5,2, Danbee Kang6
1Division of Pulmonary and Critical Care Medicine, Dept of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea.
Aim:
The impact of blood eosinophil counts on the development of chronic obstructive lung disease (COPD) is unknown. We investigated whether a higher blood eosinophil count was associated with the risk of developing obstructive lung disease (OLD) in a large cohort of men and women free from lung disease at baseline.
Methods:
This was a cohort study of 359 456 Korean adults without a history of asthma and without OLD at baseline who participated in health screening examinations including spirometry. OLD was defined as pre-bronchodilator forced expiratory volume in 1 s (FEV1)/forced vital capacity (FVC) <0.7 and FEV1 <80% predicted.
Results:
After a median (interquartile range) follow-up of 5.6 (2.9-9.2) years, 5008 participants developed incident OLD (incidence rate 2.1 (95% CI 2.1-2.2) per 1000 person-years). In the fully adjusted model, the hazard ratios for incident OLD comparing eosinophil counts of 100- <200, 200- <300, 300- <500 and ≥500 versus <100 cells·μL-1 were 1.07 (95% CI 1.00-1.15), 1.30 (95% CI 1.20-1.42), 1.46 (95% CI 1.33-1.60) and 1.72 (95% CI 1.51-1.95), respectively (ptrend<0.001). These associations were consistent in clinically relevant subgroups, including never-, ex- and current smokers.
Conclusion:
In this large longitudinal cohort study, blood eosinophil counts were positively associated with the risk of developing of OLD. Our findings indicate a potential role of the eosinophil count as an independent risk factor for developing COPD.