Anemia and hemoglobin serum levels are associated with exercise capacity and quality of life in chronic obstructive pulmonary disease

Little is known about the relationship between hemoglobin concentrations, functional status and health related quality of life (HRQL) in chronic obstructive pulmonary disease (COPD). Our aim was to investigate the prevalence of anemia and the association of hemoglobin with shortness of breath, exercise capacity, muscle strength and HRQL, in COPD patients. A total of 105 COPD patients (77 males, 71.6 ± 9.2 years) were studied. Patients were classified as anemic and non anemic using the WHO criteria. We used the Medical Research Council Dyspnoea scale (MRCs) to measure shortness of breath. Exercise capacity was assessed using the six minute walking distance (6MWD) and the peak of VO2 during the maximal cycle ergometer test (VO2max). We used the Quadriceps and Handgrip strength assessment to determine muscle strength. The Saint George Respiratory Questionnaire was used to investigate HRQL. The physiological/functional characteristics of the two groups were compared. Regression models adjusting for confounders examined the independent association of anemia and of hemoglobin levels with clinical and functional outcomes. Anemic patients (12.3%) showed a significantly higher MRCs, a lower 6MWD, VO2max, and a worse quality of life. On the contrary, there was no difference in muscle strength between the two groups. In the regression models, hemoglobin was independently associated with reduced exercise capacity and HRQL. Anemia in COPD was a risk factor for poorer exercise capacity and quality of life, and these outcomes were linearly associated with hemoglobin. Our results should stimulate further research into exploring whether increasing hemoglobin has a beneficial effect on the outcomes in COPD.