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July2012 Vol.49 Issue:      3 (Supp.) Table of Contents
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Cognitive Impairment in Hemodialysis Patients

Adel H. Gad1, Gihan M. Ramzy1, Yasser M. Abdelhamid2,

Hatem A. ElMassry3, Mohamed M. Masoud3

Departments of Neurology1, Internal Medicine2, Cairo University;

Neurology, Beni Suef University3; Egypt



Background: Patients with chronic kidney disease are at high risk for cognitive impairment due to their older age and high prevalence of stroke and cardiovascular risk factors. Methods: Using a cross-sectional design, we measured cognitive function in 50 patients with chronic kidney disease on hemodialysis for at least 1 year, ranging in age from 40 to 55 years and an age-matched comparison group in Beni Suef Hospital. Cognitive performance was measured in three domains: memory, executive function, and language. Results: As regards MMSE 66% of patients had abnormal results (score < 24). As regards trail A 68% of patients had abnormal results. As regards trail B 70% of patients had abnormal results. As regards controlled oral word association 72% of patients had abnormal results. As regards logical memory A 74% of patients had abnormal results. As regards logical memory B 76% of patients had abnormal results. As regards Beck depression scale 70% of patients had abnormal results. Conclusion: Cognitive impairment, in the form of executive dysfunction , memory and verbal learning impairment, is common and under-diagnosed in chronic kidney disease. Cognitive testing in hemodialysis patients before dialysis initiation and periodically are recommended. [Egypt J Neurol Psychiat Neurosurg.  2012; 49(3): 245-249]


Key Words: chronic kidney disease, cognitive impairment

Correspondence author: Hatem A. ELMassry, Lecturer of Neurology, Faculty of Medicine ,BenySweif University, Egypt. Email:




Chronic kidney disease (CKD) is a worldwide public health problem1. The prevalence of CKD, which was approximately 11% in both the United States and Taiwan, has increased dramatically during recent decades and may rise even further in the future2,3.

The association between end-stage renal disease and cognitive impairment has long been well recognized4,5.

Because CKD is considered treatable and preventable during its early stages6, recent studies have focused on patients with less advanced CKD. In one of these studies, moderate renal impairment, which is defined by elevated serum creatinine, was found to be associated with an increased risk of dementia7.

Other studies have suggested that general cognitive dysfunction or specific cognitive impairments are already present during the early stages of CKD8,9. However, most of these studies were conducted in elderly cohorts or in patients with co-morbid conditions8,10.

Furthermore, it is likely that there will be an increased burden of cognitive impairment in the future as the end-stage renal disease (ESRD) population ages and the prevalence of diabetes and vascular disease increases in incident dialysis patients. Evaluation of cognitive impairment in dialysis patients should include several potentially reversible neurological disorders that may acutely affect mental status and that occur with increased frequency in this population11.

It is unknown, however, how commonly cognitive impairment occurs in hemodialysis patients. Common occurrence would raise question about the ability of hemodialysis patients to comply with dialysis schedules and complex medication regiments or make informed decisions regarding initiating and continuing hemodialysis. Moderate to severe cognitive impairment is common and undiagnosed in hemodialysis patients.

This study was aiming to shed more light on severity and pattern of cognitive impairment in hemodialysis patients.




This study was conducted on 50 hemodialysis patients (Group I) recruited from hemodialysis unit in Beni Suef Hospital and 50 age and sex matched control subjects (Group II) during the period from April 2009 to August 2010.

The patient group included 25 males and 25 females ranging in age from 40 to 55 with a mean age of 48.2±4.8.


Inclusion criteria: Age ≤ 55 years, maintenance on hemodialysis for at least 1 year and normal brain-imaging (CT brain and or MRI brain).


Exclusion criteria: Age older than 55 years, disturbed conscious level, systemic diseases that affect cognitive function rather than renal disease (e.g. HTN and DM) and medications that could affect cognitive function.



1.        Thorough history taking and complete general examination.

2.        Full neurological examination according to standard neurological sheet.

3.        Routine laboratory investigations including complete blood count, calcium, phosphorous, and liver function tests, kidney function tests.

4.        Neuropsychological battery including: Mini-mental state examination (MMSE)12, The Trail Making Test13, The controlled oral word association test (COWA)14, The logical memory15, Beck Depression Inventory (BDI)16.


Statistical Methods

Descriptive analysis of the results in the form of percentage distribution for qualitative data (minimum, maximum, mean and standard deviation) calculation for quantitative data. The following tests were used: cross tabulation test, student t-test , chi-square test. Statistical package for social science (SPSS v 15) was used.




1.            Laboratory results:

All patients (100%) of group (I) were suffering from anemia with HB level ranged from 8 to 11.5 mg\dl with a mean 9.9±1.

Regarding kidney functions of group (I),blood urea ranged from 50 to 100 with a mean 69.9±14.8 and serum creatinine ranged from 3 to 9 with a mean 5.8±1.6.


2.            Neuropsychological results:

As regards MMSE, 66% of patients had abnormal results (score<24). While 68% , 70% , 72%, 74% , 76% and 77% had abnormal results in Trail A, Trail B, COWA, logical memory A and B and BDI respectively.

A statistically highly significant impairment was observed in Group I when compared to Group II regarding the results of all used psychometric tests (Table 1).

A positive correlation was found between HB level and scores in MMSE, COWA and Logical memory A, B and a negative correlation was found between HB level and scores in Color trail A, B. However, such correlations did not reach statistical significance.

A positive correlation was found between blood urea level and scores in Color trail B and BDI and a negative correlation was found between blood urea level and scores in MMSE and Logical memory A. However such correlations also did not reach statistical significance (Table 2).

Furthermore, a positive correlation was found between serum creatinine level and scores in BDI. However, such correlations did not reach statistical significance (Table 3).

Table 1. Results of neuropsychological tests in both groups.



Group I

Group II



Mean ± SD


Mean ± SD







Color trail A






Color trail B












Logical memory A






Logical memory B












* significant at p<0.01


Table 2. Correlation between blood urea level and results of neuropsychological tests.


Blood Urea Level






Color trail A



Color trail B






Logical memory A



Logical memory






Table 3. Correlation between serum creatinine and results of neuropsychological tests.


Serum Creatinine Level






Color trail A



Color trail B






Logical memory A



Logical memory B






* significant at p<0.05





Whether  cognitive dysfunction in CKD is a result of renal disease factors (i.e. metabolic disturbances) or due to the effects of other co-morbid conditions associated with this illness is poorly understood7,8,17. The aim of the current study was to characterize the pattern of cognitive functioning of adults with CKD and comparing it to age and education matched healthy controls.

In the present study all subjects were less than 55 years old to minimize the effect of aging on cognition.

In the current study, nearly 70% of participants in the CKD group had global cognitive impairment. This ratio was higher than that reported by another who reported (15%) cognitive impairment18. The discrepancy could be explained by differences in the sensitivity of the measures employed and differences in the demographic characteristics of participants between studies.

In our study, 68% of our patients had impairment of executive functions as measured by trail making test. The same study found that 38% of patients had impairment of executive functions18.

Furthermore, significant memory impairment was confirmed in our hemodialysis patients when compared to control subjects as measured by logical memory test (76%) while the other study reported 33% of memory impairment as measured by verbal learning memory test. The discrepancy could be explained by differences of the measures employed18.

Overall, in our study on verbal learning and memory extend previous findings by suggesting that the pattern of memory impairment observed in patients with CKD does not appear to be consistent with an amnesic presentation characterized by rapid forgetting, but rather that memory problems in this population may be related to deficits in attention and executive functioning, such as the ability to organize information in ways that enhance learning and recall. In terms of executive functioning, patients with CKD demonstrated significant deficits in these abilities as indicated by worse performance on color trail A, B.8 As maintained above in this study, approximately 68% of adults with CKD met criteria for cognitive impairment on this measure.

One previous study using the mini mental state examination found that 30% of 336 hemodialysis patients aged 23 to 93 years had cognitive impairment8.Our study reported that 66% of patients had cognitive impairment using the MMSE.

Anemia has been linked with cognitive impairment in the general population and in persons with ESRD.19 Furthermore, in uncontrolled studies of patients receiving hemodialysis, amelioration of severe anemia with erythropoietin is associated with improvement in cognitive function20,21. In addition, neurophysiological testing has shown improvement with the treatment of anemia in CKD.22 In this study, low hemoglobin levels were significantly correlated with cognitive impairment. Thus, it remains unclear whether anemia is a mediator or marker of other conditions, such as inflammation or nutritional deficiencies, which may contribute to cognitive impairment23.

In our study, although there was a correlation of serum creatinine and blood urea with neuropsychological performance, we do not believe that these substances are neurotoxins per se. In a previous study comparing modality of dialysis delivery, patients on continuous ambulatory peritoneal dialysis (CAPD) had better cognitive function then hemodialysis patients despite having higher levels of serum creatinine24. We, therefore, hypothesize that blood urea and creatinine are non-specific indicators of renal failure.

On the other hand, Seliger et al.7 suggested that CKD illness factors (i.e. metabolic disturbances) are linked to increased risk for developing dementia. Other findings suggest that metabolic disturbances may not be uniformly associated with deficits across cognitive domains. Decreased GFR was a significant predictor of poor performance in global cognition and delayed memory, but not of executive dysfunction18. However GFR was not included in our study due to technical difficulties.

The dialysis process may directly contribute to cognitive impairment by inducing cerebral ischemia25.

Patients with CKD have a higher prevalence of subclinical cerebrovascular and traditional vascular risk factors including hypertension, diabetes mellitus and dyslipidemia than the general population26. Non-traditional vascular risk factors including haemostatic abnormalities, hypercoaguable states, inflammation and oxidative stress may also be associated with cognitive impairment5.

The association of cognitive impairment or dementia and CKD may reflect long-term vascular disease burden manifested in two end organs, kidney and brain. This hypothesis is supported by two new cross-sectional studies demonstrating that albuminuria is associated with worse cognitive performance as well as increased white matter hyperintensity volume27,28.

The fact that the CKD sample in this study consisted of participants with no histories of neurological impairments (e. g. stroke), major psychiatric illnesses, sensory impairments (e. g. visual), etc., can be considered a limitation as this may limit the generalizability of findings to the larger population of adults with CKD. However, this possibility would only suggest that the current findings underestimate the extent of cognitive difficulties in a larger population with a higher risk burden for cognitive impairment.



Cognitive impairment, in the form of executive dysfunction, memory and verbal learning impairment, is common and under-diagnosed in chronic kidney disease. Cognitive testing in hemodialysis patients before dialysis initiation and periodically are recommended.


[Disclosure: Authors report no conflict of interest]




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الملخص العربي


التدهور العقلي في مرضى الغسيل الكلوي


إن تقييم حالات التدهور العقلي في مرض الغسيل الكلوي مهم، لأن القدرات العقلية لها تأثير مباشر على حياة المريض وأقاربه. استهدفت هذه الدراسة تقييم حالات التدهور العقلي في مرض الغسيل الكلوي مع مقارنة لعينة من الأصحاء.

تضمنت هذه الدراسة 50 مريض مصاب بالفشل الكلوي تتراوح أعمارهم بين 40 إلى 55 سنة مع 50 من الأصحاء في نفس المرحلة العمرية وتم استخدام مجموعة من الاختبارات النفسية لقياس القدرات العقلية مثل (الذاكرة – اللغة – القدرات الإخراجية) لبيان مدى التدهور في القدرات العقلية وأيضاً تم استخدام اختبار الإكتئاب لتحديد مدى انتشار الإكتئاب بين مرضى الغسيل الكلوي.

وقد وجد أن نسبة كبيرة من المرضى يعانون من الأنيميا كما وجد أن حوالي 70% من مرضى الغسيل الكلوي مصابون بتدهور في القدرات العقلية فعند استخدام اختبار قياس الذاكرة المكون من جزأين وجد أن 74% و 76% من المرضي مصابون بتدهور في الذاكرة وأيضاً عند استخدام اختبار قياس القدرات الإخراجية المكون من جزأين وجد أن 68% مصابون بتدهور في الجزء الأول و70% في الجزء الثاني وعند استخدام اختبار مقياس اللغة وجد أن 70% من المرضي يعانون من تدهور في اللغة وعند استخدام اختبار الإكتئاب وجد أن 70% من المرضي يعانون من أعراض الإكتئاب.

وقد أثبتت هذه الدراسة مدى انتشار التدهور العقلي في مرضى الغسيل الكلوي وهو ما يؤثر على حياتهم وعلى عائلاتهم كما أظهرت أهمية الكشف المبكر على القدرات العقلية لمرضى الغسيل الكلوي.


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