Chronic kidney disease comorbid with chronic obstructive pulmonary disease (COPD) was associated with increased mortality, independent of other cardiovascular comorbidities.
Chronic kidney disease (CKD) is a common comorbidity among patients with chronic obstructive pulmonary disease (COPD) that can influence mortality and other patient outcomes, according to findings from an analysis assessing the relationship between the 2 conditions.
The analysis of nearly 2300 patients with COPD enrolled in the German COSYCONET cohort study included 161 patients who also had CKD. Patients with both conditions had mortality rates that were over 2 times those seen among patients with COPD alone.
Patients with comorbid CKD more frequently reported having other comorbidities, including cardiovascular and cerebrovascular disease, peripheral artery disease, diabetes, gout, and malignancies. These patients were at an increased risk of mortality independent of other cardiovascular comorbidities.
The analysis also revealed that functional status and exercise capacity were compromised among patients with comorbid CKD, with these patients taking significantly longer to complete the Timed Up and Go Test, which assesses a person’s mobility, and walking a significantly shorter distance during a 6-minute walk test.
“Our study suggests that these negative outcomes might be mediated by an impact of CKD on symptoms, functional status and exercise capacity,” wrote the researchers. “The effects of CKD on exercise capacity cannot simply be explained by the higher frequency of these comorbidities, but suggest that CKD per se has a negative effect on exercise capacity.”
They added that the underlying mechanisms of this finding are likely complex and include increased systemic inflammation, physiological interaction between lungs and kidneys, or network effects between various comorbidities and cardiovascular diseases. CKD impacts other manifestations of COPD, including malnutrition, osteoporosis, and cardiovascular disease, which negatively affect exercise capacity and could explain these results, explained the researchers.
Using the modified British Medical Research Council dyspnea scale, the researchers showed that CKD exacerbated dyspnea in patients with COPD, which also reduced exercise capacity as measured by the 6-minute walk test. The estimated glomerular filtration rate spline interpolations showed that as kidney impairment increased, the impact on dyspnea, exercise capacity, and health status also increased.
“We therefore speculate that a higher proportion of CKD category 4 and 5 patients would have led to more pronounced differences between the two categories,” wrote the researchers.”
Laboratory testing revealed that hemoglobin was significantly lower in patients with COPD and CKD compared with patients with COPD alone, and patients with CKD had significantly elevated blood glucose and glycated hemoglobin. However, there were no differences in terms of leukocytes, C-reactive protein, or cholesterol between the 2 groups.
Trudzinski F, Alqudrah M, Omlar A, et al. Consequences of chronic kidney disease in chronic obstructive pulmonary disease [published online July 12, 2019]. Respir Res. doi: 10.1186/s12931-019-1107-x.