High hemoglobin is associated with increased in-hospital death in patients with chronic obstructive pulmonary disease and chronic kidney disease: a retrospective multicenter population-based study.

Background: Chronic kidney disease (CKD) is a common comorbidity of chronic obstructive pulmonary disease (COPD). Although high hemoglobin (Hb) is detrimental to CKD patients, its relationship with poor outcomes in the COPD population has not been reported. This study aimed to investigate the relationship between high Hb and in-hospital mortality and to explore reference Hb intervals in patients with COPD and CKD.

Methods: This retrospective study was multicenter population-based. A total of 47,209 patients who presented with COPD between January 2012 and December 2016 were included. The average Hb level during hospitalization was used as the Hb level. CKD and advanced CKD were defined as estimated glomerular filtration rates < 60 and < 30 ml/min/1.73 m, respectively. The association between Hb level (measured in 1 g/dL intervals) and in-hospital mortality was analyzed in different multivariable logistic regression models by CKD stratification.

Results: The Hb level was decreased in the CKD subgroup. In the non-CKD group, a higher Hb level was not associated with an increased risk of in-hospital death. However, the Hb level and mortality showed a U-shaped relationship in the CKD group. After adjusting for age and Charlson Comorbidity Index, multivariable regression analysis showed that an Hb level > 17 g/dL was associated with an increased risk of death in the CKD group with an odds ratio (OR) of 2.085 (95% CI, 1.019-4.264). Hb > 14 g/dL was related to an increased risk of death in advanced CKD patients (OR, 4.579 (95% CI, 1.243-16.866)).

Conclusions: High Hb is associated with an increased risk of in-hospital death in COPD patients with CKD, especially among those with advanced CKD. In this group of patients, attention should be paid to those with high Hb levels.