Longitudinal Association between Hemoglobin and Lung Function with Insights into the Incidence of Chronic Obstructive Pulmonary Disease: An Observational Study

Abstract Background Evidence regarding the long-term association between hemoglobin (Hb) level and lung function in healthy individuals is scarce. This study aimed to determine the longitudinal association between Hb level and lung function in a community-based population cohort in South Korea. Methods We used linear mixed regression analysis to evaluate the longitudinal associations between Hb levels and lung function parameters, including forced vital capacity (FVC), forced expiratory volume in 1 s (FEV₁), and FEV₁/FVC. Additionally, we used a generalized estimating equation to calculate the odds ratio (OR) of chronic obstructive pulmonary disease (COPD) according to Hb level. Results Over an 8-year biennial follow-up of 4,468 patients (median age, 53.9 years; men, 49.0%), we observed that in men, Hb levels were positively associated with lung function (estimated values of FVC: 16.7 mL, FEV₁: 15.5 mL, FEV₁/FVC: 0.18%; all P < 0.001) and a decreased incidence of COPD (OR = 0.83, P < 0.001). In women, Hb levels were positively associated with FVC but not with FEV₁ or FEV₁/FVC (estimated values of FVC: 4.7 mL, P = 0.045; FEV₁: 3.1 mL, P = 0.142; FEV₁/FVC: 0.01%, P = 0.838). The incidence of COPD was not significantly different among women (OR = 0.93, P = 0.568). In postmenopausal women, higher Hb levels were associated with increased lung function (estimated values of FVC: 11.8 mL, P < 0.001; FEV₁: 9.8 mL, P < 0.001; FEV₁/FVC: 0.09%, P = 0.052), but the incidence of COPD was not statistically significant (OR = 0.93, P = 0.568). Conclusions A decreased Hb level was associated with reduced lung function and an increased incidence of COPD in men.