Subclinical cognitive impairment in chronic kidney disease is associated with frailty and reduced quality of life.

BACKGROUND: Cognitive impairment (CI) in chronic kidney disease (CKD) is highly prevalent and is associated with multiple limitations to patients as well as a higher mortality, more days of hospitalisation and a lower quality of life. Frailty in CKD is associated with adverse health outcomes and is also highly prevalent. The aim of our study was to determine the prevalence and characteristics of CI and relate the findings to frailty, mobility, muscle strength and health-related quality of life (HRQOL). METHODS: Non-dialysis patients with CKD stages 3-5 were prospectively evaluated for inclusion. Excluded were patients with other cognitive disorders, signs of overt uraemic encephalopathy, severe infection and hyponatraemia. All patients underwent psychometric testing (five different tests): assessments of mobility, strength and frailty and an evaluation of HRQOL. Based on the number of pathological psychometric test results, we established two different definitions of CI: subclinical uraemic encephalopathy 1 (SUE1: one pathological test) and subclinical uraemic encephalopathy 2 (SUE2: two or more pathological test results). RESULTS: Sixty-two patients were included [median age 66 years (interquartile range 57-75), male 55%]. Most patients had CKD stage 3 (48%; stage 4: 32%; stage 5: 19%). CI was highly prevalent (SUE1: 60%; SUE2: 42%) and associated with a higher risk of falls (pathological tandem gait test; SUE1: 50% versus 16%, P = .023; SUE2: 69% versus 15%, P = .001), lower muscle strength (SUE2-pathological: 39% versus 7%, P = .008), frailty (SUE1: 59% versus 28%, P = .038; SUE2: 67% versus 33%, P = .028) and HRQOL. CONCLUSION: CI is highly prevalent in non-dialysis CKD patients. Even mild CI is associated with decreased mobility, muscle strength and HRQOL and increased frailty.