Intellectual impairment in chronic renal failure

Assessment of cognitive impairment and related risk factors in hemodialysis patients

Background

Cognitive impairment in hemodialysis patients has been acknowledged over the last years and has been reported in up to 80% of patients. Older age, high prevalence of cardiovascular risk factors, such as stroke and transient ischemic attack, uremia, and multiple metabolic disturbances represent the most common factors for cognitive impairment in hemodialysis patients.

Methods

We conducted a prospective cohort study on 408 patients from 10 hemodialysis centers in the regional government district of Middle Hesse (Germany). Patients underwent a neuropsychological test battery consisting of five tests, in addition to a phonemic fluency test, to assess cognitive profile. The patients were classified as no cognitive impairment or mildly-, moderately- or severely-impaired cognitive function, depending on the degree of impairment and number of domains where the deficit was determined. We analyzed the cognitive profile and the change in performance over time in hemodialysis patients based on their cognitive status at baseline vs. 1-year follow-up.

Results

Of 479 eligible patients, 408 completed all tests at baseline. Only 25% (n = 102) of the patients had no cognitive impairment. Fourteen per cent (n = 57), 36.5% (n = 149), and 24.5% (n = 100) of patients showed mild, moderate, and severe impairment, respectively. In patients with cognitive impairment, all cognitive domains were affected, and impairment was significantly associated with depression and education. The most impaired cognitive performance was immediate memory recall, and the best performance was found in naming ability. No significant  change was observed after 1-year follow up in any domain.

Conclusion

Our study shows that the prevalence of cognitive impairment in hemodialysis patients is high and that it is affected by the presence of depression. Furthermore, education has an effect on cognitive test results. As depression has a significant influence on cognitive impairment, its early identification is essential in order to initiate treatment at an early stage, hoping to positively influence cognitive performance.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40620-021-01170-3.

Abnormal rich club organization in end-stage renal disease patients before dialysis initiation and undergoing maintenance hemodialysis

Background

End-stage renal disease (ESRD) patients are at a substantially higher risk for developing cognitive impairment compared with the healthy population. Dialysis is an essential way to maintain the life of ESRD patients. Based on previous research, there isn’t an uncontested result whether cognition was improved or worsened during dialysis.

Methods

To explore the impact of dialysis treatment on cognitive performance, we recruited healthy controls (HCs), predialysis ESRD patients (predialysis group), and maintenance hemodialysis ESRD patients (HD group). All ESRD patients performed six blood biochemistry tests (hemoglobin, urea, cystatin C, Na+, K+, and parathyroid hormone). Neuropsychological tests were used to measure cognitive function. By using diffusion tensor imaging and graph-theory approaches, the topological organization of the whole-brain structural network was investigated. Generalized linear models (GLMs) were performed to investigate blood biochemistry predictors of the neuropsychological tests and the results of graph analyses in the HD group and predialysis group.

Results

Neuropsychological analysis showed the HD group exhibited better cognitive function than the predialysis group, but both were worse than HCs. Whole-brain graph analyses revealed that increased global efficiency and normalized shortest path length remained in the predialysis group and HD group than the HCs. Besides, a lower normalized clustering coefficient was found in the predialysis group relative to the HCs and HD group. For the GLM analysis, only the Cystatin C level was significantly associated with the average fiber length of rich club connections in the predialysis group.

Conclusions

Our study revealed that dialysis had a limited effect on cognitive improvement.

Neuropsychological Studies of CAPD: Preliminary Findings

A neuropsychological study of CAPD was initiated to assess potential neurotoxic complications. Results are presented for the first year of treatment. A significant improvement in psychometric performance over this time indicated that there was a substantive decline in the relative degree of neurotoxic impairment among the patients as a group. Individually, 70% of patients found to be cognitively impaired before CAPD reach normal psychometric levels by the end of the first year. A reduction in dialysis from eight to six liters/day in a limited number of highly stable patients did not increase their levels of neurotoxic impairment. Correlations between psychometric scores and biochemical indices could not be established either before or after CAPD.

Aluminium intoxication in renal disease

Aluminium intoxication in renal failure occurred over weeks or months when dialysis fluid or parenteral solutions were heavily contaminated and over many years when the main source was oral administration of aluminium-containing phosphate binders. Encephalopathy was common during subacute intoxication but in slow aluminium poisoning the main brunt was borne by the bones. However, in both tempos of intoxication several organs or systems were involved. Encephalopathy was usually accompanied by bone disease, bone disease by parathyroid suppression and both by anaemia. The heart and the lymphocytes are probably damaged by aluminium overload. Among the many questions left unanswered 15 years after the incrimination of aluminium as the cause of this multi-system illness are: (1) does low level aluminium overload in renal failure cause gradual deterioration in cerebral function? And, if so, (2) does it resemble Alzheimer's disease or a slow-onset version of dialysis encephalopathy? The evidence we review suggests that the answer to (1) is 'yes' and to (2) 'probably the latter'.

Lentidão cognitiva e psicomotora em hemodialisados crônicos

FUNDAMENTOS: A encefalopatia urêmica subclínica pode levar a comprometimento ocupacional de difícil diagnóstico por requerer o emprego de medidas sensíveis. PROPÓSITO: Testar as hipóteses de que (1) pacientes em hemodiálise crônica (HDC) se saem pior do que controles normais em uma bateria de desempenho, (2) um dia extra de uremia comprometeria ainda mais o comprometimento neuropsicológico desses pacientes, e (3) a uremia dificultaria a melhora do desempenho em uma segunda sessão de testes. MÉTODO: A agilidade cognitiva e motora de 28 pacientes em HDC foi avaliada com os testes de Trilhas (A e B), Algarismos e Símbolos, e Stroop. RESULTADOS: (1a) o desempenho cognitivo e motor se encontravam mais lento nos pacientes, (2a) um dia a mais de uremia comprometeu o desempenho na Parte B do Teste de Trilhas, e (3a) pacientes em HDC apresentaram redução da capacidade de aprender novos procedimentos. CONCLUSÃO: Pacientes em HDC podem apresentar uma "encefalopatia subclínica" cuja detecção pode requerer a aplicação de testes sensíveis. A agilidade mental e motora, e a capacidade de aprender novas rotinas estão comprometidas em, pelo menos, alguns pacientes em HDC com cognição global normal.

Acute variation in cognitive function in hemodialysis patients: a cohort study with repeated measures

BACKGROUND

Although cognitive function in hemodialysis patients is believed to be best 24 hours after the dialysis session, the extent of variation during the dialysis cycle is unknown.

STUDY DESIGN

Cohort study with repeated measures.

SETTING & PARTICIPANTS

Hemodialysis centers; patients aged 55 years or older.

PREDICTOR

Time of assessment related to the dialysis session. Time 1 (T1) occurred approximately 1 hour before the dialysis session; T2, 1 hour into the session; T3, 1 hour after; and T4, the next day.

OUTCOMES

Measures of cognitive function using a 45-minute cognitive battery. An average composite score was calculated to measure global cognitive function, equal to the average of subjects' standardized scores on all tests given at each test time. Times were classified as best and worst according to composite scores.

MEASUREMENTS

Testing was conducted on average over 2 dialysis sessions to avoid test fatigue. The cognitive battery included tests of verbal fluency, immediate and delayed verbal and visual memory, and executive function, administered at 4 times.

RESULTS

In the 28 subjects who completed testing at 3 or 4 testing times, mean age was 66.7 +/- 9.5 years and mean dialysis vintage was 44.7 +/- 33.3 months. Using a general linear model for correlated data, the composite score was significantly lower (poorer) during dialysis (T2) than shortly before the session (T1) or on the next day (T4; P < 0.001 for both).

LIMITATIONS

Relatively small sample size, testing delays, results may not be generalizable.

CONCLUSION

Global cognitive function varies significantly during the dialysis cycle, being worst during dialysis and best shortly before the session or on the day after. Clinician visits may be most effective at these times.

Chronic kidney disease and cognitive impairment in menopausal women

BACKGROUND

Although end-stage renal disease has been associated with cognitive impairment, the relation between lesser degrees of chronic kidney disease (CKD) and cognitive impairment is less well understood.

METHODS

Data for 1,015 women enrolled at 10 of the 20 Heart Estrogen/Progestin Replacement Study clinical sites were analyzed. All participants were younger than 80 years and had established coronary artery disease at study entry. Participants underwent 6 standard tests of cognitive function evaluating various domains. Unadjusted, residual age- and race-adjusted, and multivariable-adjusted linear and logistic regression models were used. Glomerular filtration rate (GFR) was estimated using the Modification of Diet in Renal Disease regression equation. In addition to analyses across the spectrum of GFRs, CKD was categorized as mild (estimated GFR [eGFR], 45 to 60 mL/min/1.73 m2), moderate (eGFR, 30 to 44 mL/min/1.73 m2), and severe (eGFR, <30 mL/min/1.73 m2) according to a modification of recently established classification guidelines.

RESULTS

Mean eGFR was 57 +/- 14 mL/min/1.73 m2. In multivariable analyses, eGFR was associated significantly with impairment in global cognition, executive function, language, and memory (approximately 15% to 25% increase in risk for dysfunction/10-mL/min/1.73 m2 decrement in eGFR). Associations among eGFR and cognitive function were independent of residual effects of age and race (2 key determinants of GFR) and the contributions of education, lifestyle factors, stroke, diabetes, and other laboratory variables.

CONCLUSION

CKD is associated with cognitive impairment in menopausal women with coronary artery disease.

Cognitive function in dialysis patients

There are few detailed studies of cognitive function in dialysis patients. However, appreciating the prevalence and risk factors for cognitive impairment is important because cognitive impairment may decrease an individual's quality of life, increase resource utilization, and result in suboptimal medical care because of difficulty following caregiver recommendations. Cognitive impairment also is likely to become more of a problem as the dialysis population ages. In this review, we argue that cerebrovascular disease is an important cause of cognitive impairment in dialysis patients and discuss risk factors specific for vascular disease, as well as other factors that may influence cognitive function. We describe the structural brain abnormalities frequently seen in dialysis patients and the specific neurocognitive changes noted in prior studies. We explore potential measures to reduce cognitive impairment in this population. We conclude that additional research is needed in this area.

Aluminium-induced changes in the rat brain serotonin system

Aluminium exposure, apart from producing cholinotoxicity, can include changes in other neurotransmitter levels since neurotransmitter levels are closely interrelated. Reports of aluminium (Al) effects on brain neurotransmitters are limited. To investigate the effect of Al on the rat brain serotonergic system, the present study was conducted to explore brain region-specific changes and duration-specific changes. Male Wistar albino rats were exposed orally to Al chloride (AlCl(3).6H(2)O; 320 mg/kg body weight) daily for up to 60 days and changes in the 5-hydroxytrytamine (5-HT) and its metabolite 5-hydroxyindole acetic acid (5-HIAA) levels were observed after 4, 14 and 60 days of exposure in olfactory lobe (OLB), cerebellum (CBL), pons (PON), medulla oblongata (MOB), spinal cord (SPI), hypothalamus (HYP), hippocampus (HIP), striatum (STR), midbrain (MBR) and cortex (COR) brain regions. Significantly increased 5-HT levels observed in brain regions OLB (60 days), HIP (4,14 days), STR (14 days), HYP (14, 60 days), MBR (4 and 14 days), PON (4 days), MOB (4 days) and SPI (4, 14 and 60 days) following Al exposure may be due to Al deactivating 5-HT system by decreased release and subsequent breakdown of 5-HT. Decreased 5-HT levels observed in cerebral COR, HIP (60 days) and in CBL after 4 and 60 days of exposure suggest an inhibitory effect of Al on the 5-HT system due to withdrawal of cholinergic input in these brain regions. 5-HIAA level changes correlate with 5-HT level changes in many brain regions studied. The results reveal that the neurochemical changes due to Al were dependent on the duration of exposure and are brain-region-specific. The observed changes may be related to the cholinergic toxicity of Al.

Depressed cerebral oxygen metabolism in patients with chronic renal failure: a positron emission tomography study

To elucidate brain oxygen metabolism in uremic patients, regional cerebral blood flow (rCBF), oxygen extraction (rOEF), and oxygen metabolism (rCMRO(2)) were measured by positron emission tomography (PET) in 10 hemodialysis (HD) patients and 13 predialysis patients with chronic renal failure (CRF). Data were compared with 20 nonuremic patients (controls) without neurological abnormalities, congestive heart failure, history of cerebrovascular accident, diabetes mellitus, or symptomatic brain lesion on magnetic resonance imaging. In the hemisphere, rCMRO(2) in both HD (1.82 +/- 0.10 mL/min/100 g) and CRF patients (1.95 +/- 0.09 mL/min/100 g) showed significantly lower values compared with controls (2.23 +/- 0.05 mL/min/100 g; P < 0.01). Hemispheric rCBF in HD (35.6 +/- 2.1 mL/100 g/min) and CRF patients (36.1 +/- 2.1 mL/100 g/min) was not different from controls (31.8 +/- 1.4 mL/100 g/min). Hemispheric rOEF in CRF patients (45.7% +/- 1.6%) was significantly greater than that in controls (40.5% +/- 1.2%; P < 0.02), but rOEF in HD patients (43.7% +/- 1.9%) did not increase significantly. These tendencies were similar in all regions of interest, especially cerebral cortices. All PET parameters in frontal cortices tended to show the lowest values in patients with renal failure. For all HD patients, rCBF in both the frontal cortex and white matter correlated inversely with HD therapy duration (P < 0.05). In conclusion, brain oxygen metabolism is depressed in patients with renal failure on or before the start of HD therapy. The cause for depressed brain oxygen metabolism is considered to be either dysregulation of cerebral circulation or lower brain cell activity.

Neurocognitive function in chronic hemodialysis patients

We administered a comprehensive neuropsychological test battery, including measures of intelligence, immediate and delayed memory, attention and mental processing speed, language abilities, complex problem solving, motor skills, and depression, to 16 well-dialyzed (Kt/Vurea = 1.46 +/- 0.24) patients with end-stage renal disease (ESRD) and 12 age- and education-matched medical controls. We observed no clear neuropsychological deficits in these ESRD patients who had low average intelligence and limited educational achievement, and hypothesize that previously observed apparent deficits resulted either from very low dialysis delivery or comparison with poorly-matched historical controls. There were significant deficits in language ability and intelligence in ESRD patients with higher than median scores on the Beck Depression Inventory compared with less-depressed ESRD patients. However, this effect of depression did not result in differences between dialysis and non-ESRD patient groups.

Beneficial effect of renal transplantation on cognitive brain function

Cognitive brain dysfunction is a common complication of end-stage renal disease. To investigate the cerebral effect of renal transplantation, we studied P300 event-related potentials--an objective marker of cognitive brain function--trailmaking test and Mini-mental state in 15 chronic hemodialysis patients and 45 matched healthy subjects. Before transplantation, patients showed prolonged P300 latency (364 vs. 337 ms, P < 0.01), smaller amplitude (15.2 vs. 19.1 microV) and scored lower (P < 0.05) in trailmaking test and Mini-mental state as compared to healthy subjects. Following renal transplantation (14 months), P300 latency decreased (337 ms, P < 0.01 vs. before) and amplitude increased (17.4 microV, P < 0.05 vs. before), indicating improved cognitive brain function. The trailmaking test and Mini-mental state tended to improve. Following transplantation, P300 findings, trailmaking test and Mini-mental state were not different from healthy subjects. Additional studies following erythropoietin treatment in 6 of the 15 hemodialysis patients revealed decreased (improved) P300 latency (351 vs. 379 ms before, P < 0.05) with further decrease following transplantation (341 ms, P = 0.06). Our findings indicate that cognitive brain dysfunction in hemodialysis patients may be fully reversed by successful renal transplantation.

Psychological testing on schoolchildren before and after pollution of drinking water in North Cornwall

The tap water supply in Camelford, North Cornwall and environs was contaminated by aluminium and other metals in 1988. Richmond tests were routinely given before and after the pollution and here scores are compared between 39 children from schools in the contaminated area and 64 children from Cornish schools outside the polluted area. The study was retrospective and it was not possible to determine whether or how much polluted water individuals had consumed. No differences were found between groups either before or after the pollution accident nor was there any evidence for any sub-group of the polluted group which had been affected. The limits of conclusions which can be drawn from data available are discussed.

Cognitive development and learning in the pediatric organ transplant recipient

Although organ transplantation is considered a viable treatment approach for end-stage organ disease, few empirical investigations have assessed the effects of transplantation on the cognitive development and learning of pediatric organ transplant recipients. This article reviews studies evaluating neurocognitive changes following organ transplantation in pediatric end-stage renal and liver disease. Despite numerous methodological problems inherent in the investigations examined, the findings of some studies are suggestive of potential neurocognitive benefits associated with organ transplantation. Recommendations are made regarding methodological improvements for future investigations assessing neurocognitive outcomes of organ transplantation.

A longitudinal study of the cognitive function of children with renal failure

Fifty-six children with chronic renal failure who either received a kidney transplant, were hemodialyzed or peritoneally dialyzed, or who were being medically managed were given a series of neuropsychological tests every 6 months for a total of four testing sessions. Each child was matched by age, sex, and race to healthy children who received the same sequence of tests. The performance of each treatment group was compared with their controls longitudinally, using a repeated measure analysis of variance. In general, renal subjects performed at lower levels than their controls on tasks of verbal ability, visual perception, memory and visual motor skills. Visual motor performance was the most clinically affected. When compared with controls, the renal subjects did not improve as much or actually deteriorated on some measures of memory and learning skills.

Disturbance of cerebral function by aluminium in haemodialysis patients without overt aluminium toxicity

The psychomotor function of 27 long-term haemodialysis patients with apparently normal cerebral function, who had only mildly raised serum aluminium (mean 59 [SEM 9] micrograms/l), was measured by means of a computerised version of the symbol digit coding test. Compared with those of control subjects matched for age and the patients' estimated premorbid IQ, the patients' response times were significantly longer (2.51 [0.10] vs 1.88 [0.05] s). Abnormalities were also detected in five other computerised tests of psychomotor function. The mean activity of erythrocyte dihydropteridine reductase (DHPR), which is inhibited by aluminium, rose during 3 months' desferrioxamine treatment in most of the 15 patients so treated. Although there was no relation between baseline psychomotor function and either indices of cumulative aluminium exposure or erythrocyte DHPR activity, changes in DHPR induced by desferrioxamine correlated with changes in psychomotor performance (r = 0.62). The flash-stimulated visual evoked potential (measured in 10 patients) was delayed (133.4 [2.4] ms), although the pattern-stimulated visual evoked potential remained normal (101.8 [3.2] ms). The difference between the visual evoked potentials stimulated by flash and pattern was significantly greater in the patients than in the controls (31.6 [4.3] vs 19.4 [2.4] ms) and was significantly related to the symbol digit coding response times and to the oral aluminium intake. The results suggest that much more rigorous exclusion of aluminium from the dialysate and diet of dialysis patients is necessary.

Olfactory identification in hemodialysis: acute and chronic effects on discrimination and response bias

The present experiment investigated the effects of renal failure and hemodialysis on olfactory identification and response bias assessed by a yes-no task administered both before and 1/2 hr after hemodialysis sessions. Identification and bias were measured under two theories. Results showed that dialysis patients had poorer identification ability overall than their controls which worsened after treatment. Patients' bias was more liberal than controls before treatment but became similar to the controls' afterwards; the bias measures Br and CL were differentially sensitive to diagnosis and time of testing effects. There was a dissociation between discrimination and bias changes in dialysis; patients' bias more closely resembled that seen in dementia (liberal) rather than depression (conservative).

Electrophysiological indices of CNS function in hemodialysis and CAPD

Fourteen Center hemodialysis (CHD) patients, 13 continuous ambulatory peritoneal dialysis (CAPD) patients, and 10 normals matched by group for age and sex were compared using a battery of evoked (EP) and event-related (ERP) brain potential measures to determine the effects on central nervous system (CNS) functioning of these two dialysis modes. While some differences were observed in early brainstem EP waves, the majority of differences occurred in the later waves associated with higher levels of cognitive processing. With tasks involving easy discriminations, CHD patients had longer latencies, indicative of less efficient cognitive processing, than CAPD patients who resembled controls. With difficult tasks, both CHD and CAPD groups showed abnormally-delayed later components. Similar results were obtained for the amplitude of the middle latency N1-P2 component, that is, reduced amplitudes for the CHD group with respect to both CAPD and control groups under low task demand, while both dialysis groups had reduced amplitudes under high task demand. These results suggest that CAPD patients are more similar to normals than CHD patients in ERP indices of attention and the efficiency of cognitive processing.

Neuropsychological deficits in arterial hypertension

Sixty subjects with uncomplicated essential hypertension and 60 matched normal subjects were submitted to neuropsychological tests in order to establish whether some impairment of cognitive functions can be evidenced even in those hypertensive subjects that are in this respect asymptomatic on standard examination and interview. The hypertensive subjects obtained significantly poorer results than normotensive subjects on memory, visuo-motor and performance tests. In the control group, the classic negative correlation pattern between age and scores was observed, while in the patient group this correlation could be confirmed only in a few tests. Subgrouping of patients according to hypertension duration and treatment showed that the impairment of cognitive functions manifested itself very early and did not tend to progress within 6-10 years of hypertension duration.

Serum and dialysate aluminium concentration of dialysed patients with chronic renal failure determined by atomic absorption spectrometry with a graphite furnace

We investigated the aluminium content in water, in solutions for haemodialysis and in serum of patients, under regular haemodialysis using flameless atomic absorption spectroscopy with l'Vov platform. The aluminium content found for tap water was 6-36 micrograms/l. After deionization the aluminium content was negligible. The dialysis bath, prepared with deionized water from a concentrated solution with 30 micrograms/l of aluminium, also showed a negligible amount of aluminium. The results obtained showed that patients who take aluminium orally have predialytic aluminium serum levels between 14 and 68 micrograms/l and between 10 and 66 after dialysis. For patients who do not take aluminium orally, the corresponding values were 12-27 and 12-24. No correlation was found between age, sex, years of dialysis and aluminium serum levels.

Chronic renal failure, dialysis, and neuropsychological function

Hemodialysis patients, nondialyzed azotemic patients and control subjects with chronic physical disabilities were tested in psychometric measures of attention, memory, and visuomotor speed and coordination. There was relatively little difference between the performance of dialysis patients and controls and no significant correlations were found between years of dialysis treatment and performance on any task. In contrast, nondialyzed azotemic patients were impaired on 9 of 14 tasks relative to controls and/or dialysis patients. Measured levels of blood urea nitrogen (BUN) and serum creatinine were significantly correlated with the performance of nondialyzed azotemic patients on several tasks. These results demonstrate a relationship between degree of renal failure and cognitive and perceptual-motor functioning. The mild impairments evident in dialysis patients do not seem to be directly attributable to dialysis treatments. Rather, the onset of hemodialysis appears to have beneficial effects on neuropsychological function.

Intellectual functioning in renal failure and chronic dialysis

The research literature on intellectual functioning in uremia and maintenance hemodialysis for renal failure is critically reviewed. The most frequently assessed neuropsychological functions have been general intelligence, memory, and attentional processes. Studies have consistently found lowered performance IQ scores compared to verbal IQ scores in renal failure patients prior to dialysis onset, suggesting the presence of intellectual deficit due to cortical dysfunction. The role of intelligence in adjustment to dialysis has not been clearly explicated, due in part to methodological variations among studies. Several studies point to significant improvement in short-term memory both after onset of maintenance dialysis and from one day before to one day after an individual dialysis treatment session. Attentional functions appear to improve after onset of dialysis treatment as well, but small sample sizes limit the conclusiveness of the data on these cortical processes. Future research efforts should be aimed at correlating physiologic with neuropsychological data and at longitudinal study of intellectual functioning in dialysis patients.

Longitudinal study of neuropsychological functioning in patients on chronic hemodialysis: a preliminary report

This study is part of a five-year project to investigate the long term effect of chronic hemodialysis on patients with end-stage renal failure. Previous research has associated hemodialysis with progressive dialysis encephalopathy (PDE), which is characterized by speech disturbances, cognitive impairment, myoclonus and behavioral changes. Little is known about the cause or the course of this syndrome except that it begins 14-36 months after treatment onset and usually culminates in death. The purpose of this study was to investigate neuropsychological (cognitive and behavioral) functioning in dialysis patients over a period of years. To date, 34 patients have been studied for 22 months utilizing a cross-sectional method comparing patients at different stages of treatment combined with a longitudinal method of repeated evaluations over time. Current findings show improved cognitive functioning during at least the first year of treatment and no evidence of cognitive deterioration in patients on dialysis for more than one year (M = 4.3). These findings offer strong evidence that PDE is not necessarily a general phenomenon among patients on chronic hemodialysis.

Research issues in psychological studies of chronic dialysis

Research examining the psychological and psychosocial effects of chronic dialysis has produced numerous controversial issues, such as the role of denial in emotional adjustment and the relationship of intelligence of vocational rehabilitation in dialysis patients. Inconsistent findings leading to these controversies are attributable in part to variance in research design and to shortcomings in methodology and reporting of data. The present article briefly reviews methodological factors not previously addressed in critiques of dialysis research, focusing on subject selection, subject description, illness measures, assessment procedures, conditions of testing, comparison groups, and data analysis. It is concluded that consideration of these factors in the design and conduct of studies will enhance the quality of research in this area.

Psychological measurement of memory deficits in dialysis patients

In light of recent research on "dialysis dementia," two questions were raised: (1) Is such dementia an all-or-none phenomenon or is it distributed in severity throughout the population of dialysis patients? (2) Is the dementia related to the uremia itself or to some aspect of dialysis? Memory decline was used as the operational definition of dementia. The Russell revision of the Wechsler Memory Scale was used to measure short- and long-term semantic and figural memory. Results suggested that both semantic and figural memory disturbances were distributed in varying degrees throughout the population of dialysis patients (n = 28). Further findings suggested that figural memory functioning was negatively correlated with the number of dialysis sessions and with the amount of time elapsed since the first dialysis session. Suggestions are made for further research and clinical considerations.

Soluble brain proteins in dialysis encephalopathy

Soluble brain proteins were analyzed regionally in a case of dialysis encephalopathy and compared to the findings in patients dying from uncomplicated uremia and acute myocardial infarction. Sixteen individual proteins were quantitated and the results may indicate that dialysis encephalopathy is accompanied by defects in the blood-brain barrier. However, such a postulated does not explain why certain proteins (gamma-trace protein) occur at very low concentrations in dialysis encephalopathy.