Kidney function and cognitive decline in frail elderly: two faces of the same coin?

Cognitive and renal impairment are pervasive among elderly frails, a high-risk, geriatric sub-population with peculiar clinical characteristics. In a series of frail individuals with non-advanced chronic kidney disease (CKD), we aimed at assessing the entity of functional, general health and cognitive impairment and the possible relationship between these types of dysfunction and the severity of renal impairment.

2229 geriatric subjects were screened for frailty and CKD. Severity of CKD was assessed by eGFR (CKD-EPI formula). Frailty was established by the Fried Index. Functional, general health and cognitive status were assessed by validated score measures.

Final analysis included 271 frail CKD subjects (162 women, 109 men). Mean eGFR was 64.25 ± 25.04 mL/min/1.73 m². Prevalence of mild-to-moderate CKD (stage 3-4) was 44%. Twenty-six percent of patients had severe cognitive impairment, while mild and moderate impairment was found in 7 and 67% of individuals, respectively. All subjects had poor functional and general health status. Cognitive capacities significantly decreased across CKD stages (p for trend < 0.0001). In fully adjusted multivariate analyses, cognitive status remained an independent predictor of eGFR (β = 0.465; p < 0.0001).

Mild-to-moderate CKD is highly pervasive among frail elderly individuals and the severity of renal dysfunction is independently correlated with that of cognitive impairment. Future studies are advocated to clarify whether the combination of kidney and mental dysfunction may portend a higher risk of worsen outcomes in this high-risk population.