Kidney function and cognitive impairment among older hospitalized patients: a comparison of four glomerular filtration rate equations

Cognitive Impairment, Chronic Kidney Disease, and 1-Year Mortality in Older Patients Discharged from Acute Care Hospital

The prognostic interaction between chronic kidney disease (CKD) and cognitive impairment is still to be elucidated. We investigated the potential interaction of overall cognitive impairment or defective constructional praxis and CKD in predicting 1-year mortality among 646 older patients discharged from hospital. The estimated glomerular filtration rate (eGFR) was calculated using the Berlin Initiative Study (BIS) equation. Cognitive impairment was assessed by the Mini Mental State Exam (MMSE) and defective constructional praxis was ascertained by the inherent MMSE item. The study outcome was 1-year mortality. Statistical analysis was carried out using Cox regression. After adjusting for potential confounders, the co-occurrence of eGFR <30 and overall cognitive impairment (Hazard Ratio (HR) = 3.12, 95% Confidence Interval (CI) = 1.26-7.77) and defective constructional praxis (HR = 2.50, 95% CI = 1.08-5.77) were associated with the outcome. No significant prognostic interaction of eGFR < 30 with either overall cognitive impairment (HR = 1.99, 95% CI = 0.38-10.3) or constructional apraxia (HR = 1.68, 95% CI = 0.33-8.50) was detectable, while only cognitive deficits were found significantly associated with the outcome in the interaction models (HR = 3.12, 95% CI = 1.45-6.71 for overall cognitive impairment and HR = 2.16, 95% CI = 1.05-4.45 for constructional apraxia). Overall cognitive impairment and defective constructional praxis may be associated with increased risk of 1-year mortality among older hospitalized patients with severe CKD. However, no significant prognostic interaction between CKD and cognitive impairment could be observed.