Cognitive function in dialysis patients

Kidney function and cognitive performance and decline in older men

OBJECTIVES

To examine the association between kidney function and cognitive impairment and decline in elderly men.

DESIGN

Observational prospective cohort.

SETTING

Community based.

PARTICIPANTS

Five thousand five hundred twenty-nine community dwelling men aged 65 and older (mean age 73.6 +/- 5.9).

MEASUREMENTS

Estimated glomerular filtration rate (eGFR) calculated using the standardized Modification of Diet in Renal Disease (MDRD) equation; cognitive function assessed using the Modified Mini-Mental State Examination (3MS) and Trail Making Test B (Trails B).

RESULTS

At baseline, 148 (2.7%) and 494 (9.1%) men were classified as cognitively impaired and, in the 5-year prospective analysis, 931 (23%) and 432 (11.6%) met the criteria for cognitive decline at follow-up defined according to 3MS and Trails B performance, respectively. In unadjusted analysis, the odds of prevalent cognitive impairment and risk of cognitive decline were significantly higher in men with an eGFR less than 45 and 45 to 59 mL/min per 1.73 m(2) than in men with an eGFR 60 mL/min per 1.73 m(2) or greater. Differences in age, race, and education between eGFR categories largely explained these associations, with the exception of the association between poorer renal function and higher odds of impairment based on Trails B test score, which persisted despite adjustment for multiple potential confounders.

CONCLUSION

This study found evidence of an independent association between mild to moderate reductions in kidney function and poor executive function at baseline but not with global cognitive impairment or risk of cognitive decline in older men.

Cognitive function in chronic kidney disease

Chronic kidney disease (CKD) is a growing public health problem. The incidence of kidney failure is rising in all age groups but particularly in older adults. Individuals in all stages of CKD are at higher risk for development of cognitive impairment and this may be a major determinant in their quality of life. Furthermore, cognitive impairment is associated with an increased risk of death in dialysis patients. Cerebrovascular disease is a strong risk factor for development of cognitive impairment and vascular disease is a more likely cause of cognitive impairment than Alzheimer's disease in patients with CKD. Both traditional and nontraditional vascular risk factors are more common in CKD and dialysis patients may also be at risk for cognitive impairment via nonvascular risk factors and the hemodialysis procedure itself. Unfortunately, because risk factors for cognitive impairment in CKD have not been thoroughly ascertained, evaluation of potential treatments has been limited. Given the high prevalence of cognitive impairment in all stages of CKD, additional studies are needed to evaluate potential risk factors and treatments in this vulnerable population.

Cognitive impairment in the aging dialysis and chronic kidney disease populations: an occult burden

The high burden of cognitive impairment in hemodialysis and chronic kidney disease (CKD) patients has only recently become recognized. Up to 70% of hemodialysis patients aged 55 years and older have moderate to severe chronic cognitive impairment, yet it is largely undiagnosed. Recent studies describe the strong graded relation between estimated glomerular filtration rate and cognitive function in CKD patients. The process of conventional hemodialysis may induce recurrent episodes of acute cerebral ischemia, which, in turn, may contribute to acute decline in cognitive function during dialysis. Thus, the worst time to communicate with dialysis patients may be during the hemodialysis session. Both symptomatic and occult, subclinical ischemic cerebrovascular disease appears to play a large role in a proposed model of accelerated vascular cognitive impairment in these populations. Severe cognitive impairment or dementia among hemodialysis patients is associated with an approximately 2-fold increased risk of both mortality and dialysis withdrawal. Predialysis cognitive screening and adding dementia to the list of comorbidities on Form 2728 would provide critical information regarding the benefit versus risks of receiving dialysis. It could also improve quality of care and outcomes by raising clinicians' awareness of the potential effects of cognitive impairment on medication, fluid, and dietary compliance and the ability to make advance directive decisions among dialysis patients. Although much remains to be learned regarding the pathophysiology of cognitive impairment in kidney disease, the public health implications of this substantial burden are immediate.

Microalbuminuria, peripheral artery disease, and cognitive function

Kidney disease may be linked to a decline in cognitive activity. We examined the association of microalbuminuria and cognitive function in a general population of older adults in the United States drawn from the National Health and Nutrition Examination Survey of 1999-2002. Cognitive function was measured by digit symbol substitution in 2,386 participants 60 years of age and older of whom 448 had microalbuminuria. Covariates included age, gender, race/ethnicity, education, smoking, diabetes, and hypertension. Among participants with peripheral artery disease, those with microalbuminuria had a significantly lower cognitive function score compared to those with a normal albumin-to-creatinine ratio. The association between microalbuminuria and cognitive function was weak in those without peripheral artery disease. But in those with peripheral artery disease, the odds of microalbuminuria associated with cognitive function in the lowest and middle tertiles was 6.5 and 3.5, respectively.

Moderate Chronic Kidney Disease and Cognitive Function in Adults 20 to 59 Years of Age: Third National Health and Nutrition Examination Survey (NHANES III)

Previous studies among elderly suggest an association between chronic kidney disease (CKD) and cognitive impairment. The purpose of this study was to determine whether moderate CKD is associated with cognitive performance among young, healthy, ethnically diverse adults. Three computerized cognitive function tests of visual-motor reaction time (Simple Reaction Time), visual attention (Symbol Digit Substitution), and learning/concentration (Serial Digit Learning) were administered to a random sample of participants, aged 20 to 59 yr, who completed initial interviews and medical examination in the Third National Health and Nutrition Examination Survey (NHANES III). Participants for this study (n = 4849) completed at least one cognitive function test. GFR was estimated using the Modification of Diet in Renal Disease (MDRD) equation. Moderate CKD was defined as estimated GFR (eGFR) 30 to 59 ml/min per 1.73 m(2). Unadjusted, residual-adjusted, and multivariate-adjusted logistic regression models were used. The cohort was 49.0% male and 11.6% black, and median (interquartile range) age was 36 yr (27 to 45) and eGFR was 107.9 ml/min per 1.73 m(2) (95.0 to 125.4). There were 31 (0.8%) prevalent cases of moderate CKD. Models were adjusted for residual effects of age, gender, race, diabetes, and other known potential confounders. In multivariate models, moderate CKD was not significantly associated with reaction time but was significantly associated with poorer learning/concentration (odds ratio 2.41; 95% confidence interval 1.30 to 5.63) and impairment in visual attention (odds ratio 2.74; 95% confidence interval 1.01 to 7.40). In summary, among those in a large nationally representative sample of healthy, ethnically diverse 20- to 59-yr-old adults, moderate CKD, reflected by eGFR 30 to 59 ml/min per 1.73 m(2), was significantly associated with poorer performance in visual attention and learning/concentration.

Patient-reported sleep difficulty and cognitive function during the first year of dialysis

BACKGROUND

Research in the general population indicates that sleep fragmentation is detrimental for cognitive function, but little attention has been given to this issue in dialysis patients. We hypothesized that patients with self-reported persistent sleep difficulty would have an increased risk of scoring lower on a cognitive function measure at follow-up compared to their score at baseline.

METHODS

Sleep difficulty and cognitive function were reported by a large national patient cohort near the start of dialysis and at a 9- to 12-month follow-up. Logistic regression was used to investigate the risk of scoring lower on a cognitive function measure at follow-up as a function of self-reported sleep difficulty, controlling for patients' sociodemographic, clinical and treatment characteristics, including depressed mood.

RESULTS

At follow-up, cognitive function scores were lower among 35.8% of the cohort. Patients with self-reported persistent sleep difficulty had the lowest average cognitive function score. Men with reported persistent sleep difficulty, regardless of presence of depressed mood, had a significantly increased risk of a lower cognitive function score at follow-up. Women with reported persistent sleep difficulty as well as depressed mood had significantly increased risk of a lower cognitive function score.

CONCLUSION

The potential impact of sleep difficulty and depressed mood on the cognitive function of dialysis patients emphasizes the importance of evaluating and treating these risks and highlights the value of continued research to improve our understanding and management of these issues.

Differential impact of age on verbal memory and executive functioning in chronic kidney disease

We compared aspects of verbal memory and executive functioning in 51 community-dwelling persons with chronic kidney disease (CKD) and 55 healthy controls matched on age and education. Depressive symptoms were assessed with the Centre for Epidemiological Studies-Depression Scale (CES-D), and illness variables included glomerular filtration rate (GFR) and hemoglobin. Findings indicate that persons with CKD exhibited poorer performance on measures of memory (CVLT-II) and executive functioning (DKEFS Trailmaking Test B and Color-Word Interference Tests) in comparison with healthy controls. Furthermore, performance decrements were magnified in older CKD participants on measures of verbal memory and inhibition. Nearly half of CKD participants aged 61 and older exhibited significant impairments in verbal memory and inhibition in comparison to matched controls. Cognitive performance in CKD was not associated with measures of illness severity. The differences observed were not accounted for by depressive symptoms, which were only weakly associated with cognitive performance, and negatively associated with age. Findings highlight the need for further exploration of the etiologies and functional consequences of the neuropsychological presentation of CKD.

La population âgée hémodialysée : évaluer et prendre en charge le risque de déclin cognitif

Epidemiological data suggest a large prevalence of cognitive impairment in elderly patients on haemodialysis. They are frequently exposed to pathologies that affect the brain, and hold a plurality of risk factors for neurodegenerative and vascular dementia. Cognitive dysfunctions, because of their medical and socio-economical consequences, may led to discuss the indication for haemodialysis and its profit for the elderly patient. These facts highlight the advantage of a regular assessment of cognitive functions in this population. They also suggest the need in the future of a multidisciplinary intervention for these patients, for a better evaluation of interventions aimed on primary and secondary prevention of cognitive decline in the elderly group.

Association of sleep difficulty with Kidney Disease Quality of Life cognitive function score reported by patients who recently started dialysis

Sleep disorders are associated with impaired cognition in the general population, but little attention has been given to the potential association between sleep and cognitive function in the dialysis population. This study investigated reported sleep difficulty and cognitive function scores in a national cohort of patients who initiated maintenance hemodialysis and peritoneal dialysis. The cognitive function scale of the Kidney Disease Quality of Life instrument (KDQOL-CF), which measures aspects of cognitive ability that are important for daily functioning (perceived reaction time, ability to concentrate, and tendency to become confused), was used. The study population included 2286 patients who responded to a questionnaire at baseline in the US Renal Data System Dialysis Morbidity and Mortality Study Wave 2. Reported sleep difficulty was associated in a univariate manner with lower KDQOL-CF score. In a multivariable regression analysis that controlled for age, gender, race, education, diabetic ESRD, cardiovascular comorbidity, smoking, hemoglobin, serum albumin, prescribed sleep medications, dialysis modality, pre-ESRD care, bodily pain, and depressed mood, the association of sleep difficulty with KDQOL-CF score remained significant (P < 0.0001); the association also was significant in a multivariable analysis that was restricted to hemodialysis patients and included adjustment for Kt/V (P = 0.001). Depressed mood and sleep medication prescription predicted a lower KDQOL-CF score, and higher educational level and less bodily pain predicted a higher KDQOL-CF score. Increased understanding of links among sleep difficulty, management of sleep difficulty, and cognitive function could benefit multiple dimensions of dialysis patients' quality of life and daily functioning.

Cognitive function in Stage 5 chronic kidney disease patients on hemodialysis: no adverse effects of lanthanum carbonate compared with standard phosphate-binder therapy

Patients with Stage 5 chronic kidney disease who have hyperphosphatemia require treatment with phosphate binders to lower serum phosphorus levels. Existing binders are effective but may be associated with important safety disadvantages. Lanthanum carbonate is a phosphate binder with demonstrated efficacy, safety, and tolerability in clinical trials. Changes in cognitive function were evaluated over time using the Cognitive Drug Research computerized cognitive assessment system (Simple Reaction Time, Digit Vigilance Task, Choice Reaction Time, Numeric Working Memory, and Delayed Picture Recognition) in 360 hemodialysis patients who were enrolled in a 2-year, multicenter, comparative study of lanthanum carbonate versus standard therapy. A decline in cognitive function from baseline was observed in both groups. The deterioration in cognitive function was similar in both the lanthanum carbonate and standard therapy groups. One parameter - Numeric Working Memory - showed a statistically significant between-group difference in favor of lanthanum carbonate (P=0.02). Given the magnitude of the changes, however, and the differences that were observed at baseline between treatment groups, the clinical significance of this difference is doubtful. This study demonstrates that cognitive function deteriorates in hemodialysis patients over a 2-year time period. Use of lanthanum carbonate as a phosphate binder does not adversely affect cognitive function compared with standard therapy.

Dementia as a predictor of mortality in dialysis patients

The life expectancy of patients who have dementia and are initiated on dialysis in the United States has not been described in the medical literature. A retrospective cohort study was conducted of 272,024 Medicare/Medicaid primary patients in the US Renal Data System who were started on ESRD therapy between April 1, 1995, and December 31, 1999, and followed through December 31, 2001. Cox regression was used to calculate adjusted hazard ratios for risk for death after initiation of dialysis for patients whose dementia was diagnosed before the initiation of dialysis as shown by Medicare claims. The average time to death for patients with dementia was 1.09 versus 2.7 yr (P < 0.001) with an adjusted hazard ratio of 1.87 (95% confidence interval 1.77 to 1.98). The 2-yr survival for patients with dementia was 24 versus 66% for patients without dementia (P < 0.001 via log rank test). Dementia that is diagnosed before initiation on dialysis is an independent risk factor for subsequent death. Such patients should be considered for time-limited trials of dialysis and careful discussion in choosing whether to pursue initiation of dialysis or palliative care.

Silent Cerebral White Matter Lesions and Their Relationship With Vascular Risk Factors in Middle-Aged Predialysis Patients With CKD

BACKGROUND

Silent cerebral white matter lesions are observed on magnetic resonance imaging (MRI) scans in elderly people, and they are related to vascular risk factors, particularly hypertension. No data on the prevalence and risk factors of white matter lesions in patients with chronic kidney disease (CKD) are available. The aim is to analyze the prevalence of white matter lesions and their determinants in this population.

METHODS

We studied 52 patients without diabetes with CKD (stage 3 or 4) aged 30 to 60 years (average, 49 years) and a group of 32 normotensive control subjects. MRI studies were performed and subcortical and periventricular white matter lesions were evaluated by using semiquantitative measures. Patients were classified into 2 groups depending on the presence or absence of white matter lesions. Echocardiographic studies and measures of markers of systemic inflammation (C-reactive protein and interleukin 6) also were performed.

RESULTS

White matter lesions were more prevalent in patients with CKD than controls (33% versus 6%; P = 0.008). Patients with CKD who had white matter lesions were older; had a greater history of cardiovascular disease and vascular nephropathy as a primary cause of renal disease and greater levels of systolic blood pressure, pulse pressure, left ventricular mass index, and C-reactive protein; and were administered more antihypertensive drugs than patients with CKD without white matter lesions. Stage and duration of CKD were not related to the presence of white matter lesions. After adjusting for several factors, only vascular nephropathy (odds ratio, 15.6; 95% confidence interval, 1.27 to 191.54; P = 0.03) independently predicted an increased risk for white matter lesions.

CONCLUSION

One third of middle-aged patients with CKD have silent cerebral white matter lesions. Vascular nephropathy seems to be the most important factor related to the presence of these lesions, suggesting that white matter lesions reflect ischemic brain damage caused by generalized vascular damage.