Cognitive function and the risk of death in chronic kidney disease

Cognitive impairment is a risk factor for death in dialysis patients and the general population. We sought to determine if cognitive impairment is associated with death in people with non-dialysis-dependent chronic kidney disease (CKD), and if so, whether this relationship is greater in the CKD population compared to the general population.

National Health and Nutrition Examination Survey-III participants older than 60 years were asked to subtract 3 from 20 five times and to perform immediate and delayed recall of three items. A cognitive score of 0-11 was assigned based on the number of correct responses. Participants were categorized according to cognitive score (11, 9-10, 6-9, and 0-5) and CKD status. Survival analyses were conducted using Cox models.

Within the CKD subpopulation, those in the lowest cognitive score group had a twofold increased hazard of death compared to those with maximum score. Within the non-CKD subpopulation, those in the lowest cognitive score group had a 46% increased hazard of death compared to those with maximum score. However, the difference in the hazards of death in the CKD and non-CKD subpopulations with the lowest cognitive score was not significant (p = 0.99).

Low cognitive score is associated with an increased risk of death in elderly individuals with and without CKD; however, there was no interaction of CKD and low cognitive score in this analysis.