Consequences of chronic kidney disease in chronic obstructive pulmonary disease

Abstract

Background: The combination of chronic obstructive pulmonary disease (COPD) and chronic kidney disease (CKD) is associated with a higher prevalence of comorbidities and increased mortality. The impact of kidney function on patient-centered outcomes in COPD has not been evaluated.

Methods: Patients from the German COPD and Systemic Consequences - Comorbidities Network (COSYCONET) cohort COPD were analysed. CKD was diagnosed if the estimated glomerular filtration rate (eGFR) measurements were < 60 mL/min/1.73m² at study inclusion and six month later. The effect of CKD, on comorbidities, symptoms [modified British Medical Research Council dyspnoea scale], physical capacity [six-minute walk test, and timed up and go] and St George's Respiratory Questionnaire were analysed. Restricted cubic spline models were used to evaluate a nonlinear relationship between eGFR with patient-centered outcomes, cox survival analysis was applied to evaluate mortality.

Results: 2274 patients were analysed, with CKD diagnosed in 161 (7.1%). Spline models adjusted for age, gender, BMI, FEV₁ and cardiovascular comorbidities revealed independent associations between eGFR with modified British Medical Research Council dyspnoea scale, St George's Respiratory Questionnaire, (p < 0.001 and p = 0.011), six-minute walk test (p = 0.015) and timed up and go (p < 0.001). CKD was associated with increased mortality, independently from for other cardiovascular comorbidities (hazard ratio 2.3; p < 0.001).

Conclusion: These data show that CKD is a relevant comorbidity in COPD patients which impacts on patient-centered outcomes and mortality.

Trial registration: NCT01245933.

Keywords: Chronic kidney disease; Chronic obstructive pulmonary disease; Cohort study; Patient-centered outcomes.

Fig. 1

Restricted cubic spline plots of the association of eGFR with (a) Modified British Medical Research Council dyspnoea scale; mMRC, (b) timed up and go TuG in seconds, (c) six-minute walk test in meters, (d) St George’s Respiratory Questionnaire; SGRQ, (e) forced expiratory volume in 1 s; FEV1 in % predicted and (f) body mass index; BMI. The red line indicates the estimated change of mMRC, TuG, 6MWT, SGRQ, FEV1 (%pred.) with the respective 95% confidence interval (gray area). a-d are adjusted for age, gender, BMI, FEV1 (% pred.) and cardiovascular comorbidity (CVI 1–5). e and f for age, sex, cardiovascular comorbidity (CVI score) and either BMI or FEV1 (% pred.)

Fig. 2

Cox analysis with BMI, sex, packyears, CVI, and FEV1% pred. as cofounders showed that CKD is significantly associated with mortality