Hemodialysis (HD) patients demonstrate impaired cognitive function, particularly in the domains of orientation and attention and executive function, a new review and meta-analysis confirms.

The impairments particularly affect attention, processing speed, and working memory. HD patients’ scores for attention and memory were worse than the general population’s, but better than scores from non-dialyzed kidney failure patients. HD patients also performed slightly worse in memory than people with non-dialysis-dependent chronic kidney disease (CKD). Data on peritoneal dialysis patients were insufficient for a meaningful comparison.

“Cognitive deficits in specific domains should be further explored in this population and should be considered when approaching education and chronic disease management,” Emma O’Lone, MBChB, of Sydney Medical School in Australia, and colleagues concluded in an online report in the American Journal of Kidney Diseases.

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The investigators reviewed 42 studies and pooled data from 3,522 participants for the analysis. They adjusted results for age, but were unable to determine the influence of education and co-existing illnesses, such as cardiovascular diseases. Many studies excluded patients with dementia; however, the investigators did consider the potential impact of aluminum-related dementia from aluminum used in dialysate.

HD patients have risk factors for cognitive impairment, including hypertension, diabetes, and dyslipidemia, Dr. O’Lone and colleagues noted in the review’s background information. HD patients also are exposed to hypoxemia, fluid and osmolar shifts, fluctuating uremic toxin titers, and a proinflammatory state.

These patients need cognitive skills to access health services, understand clinicians’ instructions, and make health care decisions. Impairment can reduce health literacy, medication adherence, harm health, and increase the risk of early death. Clinicians treating HD patients need to bear this in mind, especially when discussing options in renal replacement therapy or transplantation and when educating patients about these therapies. 

Notably, the difference in scores between dialyzed and non-dialyzed patients suggests that cognitive deficits may be partially reversible. Previous research by the investigators published in Transplantation also found cognitive improvement after kidney transplantation (2014;98:845-846).

The investigators acknowledged high heterogeneity between studies due to the variety of neuropsychological tests used. They suggested future research would benefit from an agreed standard tool for measuring cognition in CKD.


  1. O’Lone E, Connors M, Masson P, et al. Cognition in People With End-Stage Kidney Disease Treated With Hemodialysis: A Systematic Review and Meta-analysis. Am J Kidney Dis. doi: 10.1053/j.ajkd.2015.12.028.