Cognitive impairment and 7-year mortality in dialysis patients

Abstract

Background: Although dementia has predicted mortality in large dialysis cohorts, little is known about the relationship between less pronounced cognitive deficits and mortality in patients with end-stage renal disease. This study assessed whether cognitive impairment without dementia was an independent predictor of 7-year survival in dialysis patients after controlling for other risk factors.

Study design: Prospective single-cohort study.

Setting & participants: 145 prevalent dialysis patients from 2 units in London, UK, were followed up for 64.3 ± 27.4 months and censored at the time of change to a different treatment.

Predictors: Cognitive impairment, defined as performance 1 standard deviation less than normative values on 2 or more cognitive tests within a neurocognitive battery assessing attention/concentration, memory, and psychomotor function domains. Depression, quality-of-life, and clinical measures also were obtained.

Outcomes & measurements: All-cause mortality was the primary outcome. Cox proportional hazard models were used to assess the contribution of demographics and clinical and psychological measures and cognitive impairment to mortality.

Results: 98 (67.6%) patients were cognitively impaired at baseline. At follow-up, 56 (38.6%) patients had died, 29 of cardiac causes. Unadjusted Kaplan-Meier analysis showed higher mortality in cognitively impaired patients, in whom 7-year survival was 49% versus 83.2% in those with no cognitive impairment (P < 0.001). Mortality risk associated with cognitive impairment remained significant in adjusted analysis controlling for sociodemographic, clinical, and psychological factors (adjusted HR, 2.53; 95% CI, 1.03-6.22; P = 0.04).

Limitations: Small sample size and number of events.

Conclusions: Cognitive impairment is an independent predictor of mortality in dialysis patients. Although the implications of early recognition and treatment of cognitive impairment for clinical outcomes are unclear, these results suggest that patient management protocols should attempt to ensure prevention of cognitive decline in addition to managing coexisting medical conditions.