10.14718/ACP.2026.29.9

Artículo Cognitive Profile of Patients with Early-Stage Chronic Kidney Disease and Low Educational Attainment Perfil cognitivo en pacientes con enfermedad renal crónica en estadios tempranos y baja escolaridad

Diana Patricia Caicedo Navarro ¹
Gladys Eugenia Puentes Páramo ²
Natalia Cadavid-Ruiz ^3*

¹ Pontificia Universidad Javeriana, Cali, Colombia
0000-0003-4041-7735

² Pontificia Universidad Javeriana, Cali, Colombia
0009-0009-1319-8304

³ Pontificia Universidad Javeriana, Cali, Colombia
0000-0002-3699-5068

^* Corresponding autor : Cl. 18 #118-250, Barrio Pance, Cali, Valle del Cauca, Colombia.
ncadavid@javerianacali.edu.co

Author Note: The authors thank the participants and the healthcare institutions that facilitated the development of this study. No datasets, computer code, or other research materials requiring deposition in open-access repositories were generated. Additional information about the study may be requested from the corresponding author. This manuscript does not reproduce tables, figures, images, instruments, or other copyrighted materials requiring additional permission for publication. This study was conducted as part of a master's thesis in clinical neuropsychology.

Conflict of Interest: The authors declare that they have no conflicts of interest related to the subject matter, results, or publication of this study. This research received no external funding and was not conducted as part of a project funded by public or private institutions.

Received: April 26, 2024,
Reviewed: January 29, 2026,
Accepted: June 4, 2026

How to cite [APA]: Caicedo, D. P., Puentes, G. E., y Cadavid-Ruiz, N. (2025). Perfil cognitivo en pacientes con enfermedad renal crónica en estadios tempranos y baja escolaridad. Acta Colombiana de Psicología, 29, 1-15. https://doi.org/10.14718/ACP2026.29.9

Abstract

This study aimed to compare the cognitive profile of patients with early-stage chronic kidney disease (CKD) and low educational attainment with that of matched controls and to preliminarily explore which neuropsychological measures have the greatest discriminative ability in this sample. A cross-sectional observational study with exploratory logistic regression analyses was conducted, including 60 participants: 30 patients with CKD and 30 healthy controls matched for age (M= 51, SD = 7.00), sex (70% women), and educational attainment (56% with five years of education). All participants were assessed using the MoCA cognitive screening test and four neuropsychological tests to evaluate: attention (Trail Making Test-B, TMT -b), processing speed and inhibition (STROOP), working memory (Digit Span subtest of the Wechsler intelligence scale, WAIS-IV), and long-term verbal memory (Hopkins Verbal Learning Test). As a result, the patient group showed poorer performance on the abstraction subtest of the cognitive screening test, in the TMT-b completion time, and the STROOP interference measure. The binary logistic regression showed that these tests constituted predictor variables, with a sensitivity of 63.3% and a specificity of 73.3%. These findings suggest that patients with early-stage CKD may present difficulties in processing speed and abstract reasoning, indicating possible predominantly frontal dysfunction. However, this finding should be considered preliminary and requires validation in a larger sample.

Keywords: Chronic kidney disease, cognitive impairment; educational attainment; neuropsychological tests; diagnosis; health equity.

Resumen

El objetivo de este estudio fue comparar el perfil cognitivo de pacientes con enfermedad renal crónica (ERC) en estadios tempranos y baja escolaridad frente a controles pareados, y explorar preliminarmente qué medidas neuropsicológicas muestran mayor capacidad discriminativa en esta muestra. Se realizó un estudio observacional con análisis exploratorio de regresión logística, de corte transversal, en el que participaron 60 personas, 30 pacientes con ERC y 30 sujetos sanos, pareados por edad (M=51, DE = 7.00), sexo (70 % mujeres) y escolaridad (56 % con cinco años de educación). Todos los participantes fueron evaluados con la prueba cognitiva de rastreo rápido moca y cuatro subpruebas neuropsicológicas, con el fin de evaluar: la atención (Trail Making Test-b, TMT-B), la velocidad de proces­amiento e inhibición (STROOP), la memoria de trabajo (subtest de retención de dígitos de la escala de inteligencia Wechsler, WAIS-IV) y la memoria de largo plazo verbal (test de aprendizaje verbal de Hopkins). Como resultado, el grupo de pacientes mostró un menor desempeño en la subprueba de abstracción del test de rastreo rápido, en el tiempo del TMT-B y en la medida de interferencia del STROOP. El modelo de regresión binaria mostró que las pruebas mencionadas conforman las variables predictoras, con una sensibilidad de 63.3 % y una especificidad del 73.3 %. De lo anterior se concluye que en estadios tempranos de ERC se pueden presentar dificultades en la velocidad de procesamiento y en el razonamiento abstracto, lo cual sugiere una posible afectación de predominio frontal. No obstante, este hallazgo es preliminar y requiere de una validación con una muestra más amplia.

Palabras clave: Enfermedad renal; deterioro cognitivo; escolaridad; pruebas neuropsicológicas; diagnóstico; equidad en salud.

Introduction

Over the past decades, clinical neuropsychology has shown growing interest in the cognitive functioning of patients with chronic kidney disease (CKD) (Arango-Lasprilla et al., 2022; Tian et al., 2019), because impairments in communication between the kidneys and the autonomic nervous system may result in sodium accumulation in the brain. This, in turn, produces oxidative stress in this tissue and triggers a neuroinflammatory response that, over time, may lead to uremic encephalopathy (Bos et al., 2018; Crowe et al., 2021; Drew et al., 2019; Murthy & Shukla, 2020; Soto-Añari et al., 2018; Tanaka & Okusa, 2020).

Studies such as those conducted by Fraser and Arieff (1988) and Kimmel et al. (1998) suggest that the cognitive functioning of patients with CKD is adversely affected in the early stages of the disease, and that patients in the more advanced stages may develop dementia, with a prevalence twice that observed in the general population.

Likewise, the scientific literature has described that, during the first two stages, cognitive difficulties may go unnoticed by both patients and their treating physicians, the most common being reduced processing speed, attention, and short-term memory (Berger et al., 2016; Brodski et al., 2018; Drew et al., 2019; Harhay et al., 2018; Joseph et al., 2019; Owolabi et al., 2016; Pi et al., 2016). During stage 3, or the mild-to-moderate stage, executive dysfunction is also observed, whereas in stages 4 and 5, known as the end stage, generalized cognitive impairment is observed, together with deficits in working memory, long-term memory, visuospatial skills, language, and praxis (Brodski et al., 2018; Drew et al., 2019; Duarte et al., 2006). During these latter stages, patients may develop uremic encephalopathy and even dementia, depending on the severity of the cognitive symptoms and the limitations they impose on patients' performance of activities of daily living (Arnold et al., 2016; Duarte et al., 2006; Feger et al., 2020).

However, identifying cognitive impairment in patients with CKD in clinical settings is challenging, as performance on neuropsychological tests is influenced by both sociodemographic and clinical factors. This means that CKD is not the sole factor that may determine a patient's cognitive performance on a given test (Brickman et al., 2006). For example, years of formal education, reading proficiency, medication effects, and mood have been shown to affect performance on cognitive tests (Brickman et al., 2006; Joseph et al., 2019; Roebuck-Spencer et al., 2017).

General cognitive screening instruments, such as the Montreal Cognitive Assessment (MoCA) and the Mini-Mental State Examination (MMSE), are often used in the cognitive assessment of patients with CKD, together with specific tests that allow the assessment of cognitive processes frequently affected, including attention, cognitive flexibility, working memory, and reasoning (Crowe et al., 2021; Soto-Añari et al., 2018). Among the most commonly used are the Trail Making Test (Reitan, 1958), the STROOP Color and Word Test (Golden, 2020), the Tower of Hanoi (Drake, 2007), and the Digit Span subtest of the Wechsler Adult Intelligence Scale, WAIS-IV (Wechsler, 2014). These tests have demonstrated sensitivity in detecting early deficits in sustained attention, processing speed, and inhibitory control in patients with CKD, even before overt clinical symptoms become evident (Feger et al., 2020; Karakizlis et al., 2021).

However, psychometric studies of neuropsychological tests have reported the presence of false-positive results among patients with low educational attainment. For example, although the Mini-Mental State Examination has proven useful for confirming severe cognitive impairment in Spanish-speaking individuals with more than five years of education, it is not recommended for patients with low educational attainment, as it tends to indicate cognitive impairment in otherwise healthy individuals (Owolabi et al., 2016; Sagubay et al., 2017).

Similarly, studies involving patients diagnosed with CKD have shown that low educational attainment is associated with a greater number of perseverative errors on the Trail Making Test, Part B (TMT-B), and with a greater number of moves required to solve the Tower of Hanoi. This may be related to lower levels of knowledge and experience in cognitive tasks, rather than to deficits in cognitive processes (Soto-Añari et al., 2018).

Indeed, most studies on the progression of cognitive impairment in patients with CKD have been conducted in developed Western countries, where populations tend to be more homogeneous with respect to sociodemographic  variables, such as socioeconomic status and educational attainment. This has led to the acceptance of an association between the degree of renal impairment and the severity of cognitive deficits (Brickman et al., 2006; Roebuck-Spencer et al., 2017). Nevertheless, few studies have examined the effect of educational attainment on this relationship, and those that have found that the impact of CKD is greater among patients with low educational attainment than among those with higher educational attainment (Soto-Añari et al., 2018).

In this context, it remains unclear which tests should be administered or which cutoff scores should be used to accurately determine the presence of cognitive impairment in patients with CKD. This is particularly critical during the early stages of the disease, when subtle cognitive symptoms tend to emerge. In patients with higher educational attainment, these symptoms may be masked by greater cognitive reserve, whereas in patients with low educational attainment they may result in false-positive findings (Soto-Añari et al., 2018).

Overall, recent literature has shown that educational attainment and cognitive reserve modulate the expression of cognitive impairment in patients with CKD. Specifically, individuals with low educational attainment tend to obtain lower scores on tasks assessing cognitive flexibility and planning, such as the TMT-b and the Tower of Hanoi, even in the absence of structural neurological damage (Soto-Añari et al., 2018).

This evidence underscores the need to develop cognitive screening protocols tailored to educational attainment in order to avoid overestimating the number of cases (false positives) and to allow a more contextualized interpretation of cognitive performance. Moreover, few studies have examined cognitive symptoms associated with CKD during the early stages of the disease.

Accordingly, the present study aimed to compare the cognitive profile of patients with early-stage chronic kidney disease (CKD) and low educational attainment with that of matched controls, and to conduct a preliminary exploration of which neuropsychological tests show the greatest discriminative ability in this sample. From this perspective, the findings of the present study seek to expand previous models of cognitive impairment in CKD by highlighting the role of educational attainment and cognitive reserve in trajectories of cognitive decline and in the early identification of subtle changes in cognitive functioning.

Method

Design

A quantitative observational study with a cross-sectional case-control comparative design was conducted. In addition, an exploratory binary logistic regression analysis was performed (Ato et al., 2013).

Participants

The sample was selected using a purposive, non-probability sampling method. The group of patients with early-stage CKD and low educational attainment was recruited from the patient registry of the nephroprotection program of the nephrology services at public hospitals and healthcare provider institutions in rural areas of southwestern Colombia. Each patient underwent evaluation by a nephrologist, who confirmed the stage of the disease. Inclusion criteria were: (a) age between 27 and 60 years; (b) a maximum of five years of education; and (c) stages 1 or 2 CKD, according to the K/DOQUI Guidelines of the National Kidney Foundation (2012).

The healthy control group (n = 30) consisted of family members of the patients, as well as individuals with no self-reported history of kidney disease. These participants were matched to the patient group for age, sex, and educational attainment.

Exclusion criteria for both groups were: (a) current hospitalization; (b) an uncorrected sensory impairment that could affect performance on the neuropsychological tests; (c) a diagnosis of a neurological and/or psychiatric disorder; (d) current use of medication known to affect neurological functioning; and (e) more than five years of education.

Clinical variables with the potential to influence cognitive performance, such as time since diagnosis, the presence of comorbidities (e.g., diabetes and hypertension), and current medical treatment, were controlled. These variables were verified through medical records and structured interviews with both the participants and their treating physicians. The assessments were conducted by two trained psychologists under the supervision of a clinical neuropsychologist, who held weekly calibration meetings to ensure inter-rater consistency and the standardized administration of the tests.

A total of 161 patients with kidney disease were screened, of whom only 30 met the inclusion and exclusion criteria. Based on their sociodemographic characteristics, a control group was assembled to ensure appropriate matching. At this stage, no significant differences were found between the two groups in age (U = 399, z = -.75, p = .450), educational attainment (U=447, z = -.49, p = .961), or socioeconomic stratum (U=403, z = -.91, p = .369).

Instruments

The neuropsychological assessment battery consisted of one cognitive screening test and four neuropsychological tests, which are among the instruments most frequently used in patients with CKD (Brodski et al., 2018; Owolabi et al., 2016; Pi et al., 2016; Soto-Añari et al., 2018).

Instrument selection was based on documented evidence of validity and sensitivity for assessing the cognitive domains reported to be most vulnerable in CKD, particularly attention, working memory, cognitive flexibility, and processing speed. These tests have demonstrated sound psychometric properties, have normative data developed for the Colombian population, and have been employed in previous studies on cognitive dysfunction in patients with CKD (Crowe et al., 2021; Faria et al., 2020; Soto-Añari et al., 2018). Instruments suitable for administration to participants with low educational attainment were prioritized in order to minimize educational bias in the interpretation of the results.

The Montreal Cognitive Assessment (MoCA) cognitive screening test was selected because of its widespread use for detecting cognitive impairment, its score adjustment for individuals with fewer than 12 years of education, its validation in the Colombian population, and its reported reliability of Cronbach's a = .75 and convergent validity of r = .72 with the MMSE (Pedraza et al., 2016; Pereira-Manrique & Reyes, 2013).

The MoCA comprises eight cognitive domains (abstraction, attention, naming, visuospatial/executive skills, language, memory, orientation, and delayed recall) distributed across 19 items (Delgado et al., 2019; Rossetti et al., 2011). Total scores range from 0 to 30 points. The generally accepted cutoff score for mild cognitive impairment (MCI) is 25 points, whereas a score of17 indicates dementia. For individuals with low educational attainment, a cutoff score of 21 points has been recommended for the detection of mci, based on a validation study conducted in adults from the city of Bogotá (Pedraza et al., 2016). Test-retest reliability was moderate, with a Lin's concordance correlation coefficient of 0.62, an internal consistency of 0.85, criterion validity of 0.66, and an acceptable roc curve performance (AUC=0.76 for mci and 0.81 for dementia) (Pedraza et al., 2016).

Regarding the neuropsychological tests, four instruments were administered:

a)   The STROOP Color and Word Test (Golden, 2020), which has normative data for the Colombian population (Arango-Lasprilla et al., 2022) and is used to assess inhibitory control and processing speed. Specifically, the test consists of three sheets, each containing 100 stimuli arranged in five columns of 20 stimuli each. The first sheet is composed of the words RED, CREEN, and BLUE, randomly ordered and printed in black ink on an 8.5 x 13-inch sheet of paper. No word appears twice consecutively within the same column. The second sheet contains 100 stimuli consisting of Xs (XXX) printed in blue, green, or red ink. The third sheet contains the words from the first sheet printed in the colors used on the second sheet, with the ink color never matching the color name.

b)   The Trail Making Test, Part B (TMT-B) (Reitan, 1958), which has psychometric normative data for the Colombian population (Arango-Lasprilla et al., 2022), was used to assess attention and processing speed.

c)   The Hopkins Verbal Learning Test (HVLT-R) (Brandt, 1991), which has Colombian normative data (Arango-Lasprilla et al., 2022), is a brief test that assesses verbal learning and memory based on a list of 12 words divided into three semantic categories and presented across three consecutive learning trials. After a 20-minute delay, the examinee is asked to recall all the words from the original list (Benedict et al., 1998; Brandt, 1991).

d)   The Digit Span subtest of the Wechsler Adult Intelligence Scale (WAIS-IV) (Wechsler, 2014) was included as a measure of working memory because it is one of the most widely used measures for assessing this cognitive domain, is easy to administer, and places relatively low demands on formal education (Rosas et al., 2014; Wechsler, 2014).

All tests used to assess cognitive functioning have normative data for the Colombian adult population, generated using multiple regression models, with norms adjusted for age and educational attainment (Arango-Lasprilla et al., 2022).

Procedure

This study was reviewed by the Ethics and Research Committee of the Pontificia Universidad Javeriana Cali (Minutes No. FHCS 57 of 2023). Following receipt of this approval, authorization was requested from public hospitals in both urban and rural areas of Valle del Cauca that offered nephroprotection programs in order to identify, through this service, patients who met the study's inclusion and exclusion criteria and invite them to participate. Those who gave verbal consent were scheduled for an assessment session during which the purpose of the study was explained, eligibility criteria were confirmed, and those who agreed to participate signed an informed consent form. An initial interview was then conducted to collect the patients' sociodemographic information, followed by the neuropsychological assessment, which was administered by two master's students in clinical neuropsychology who had received prior training in the administration of the tests selected for this study.

Participants in the healthy control group were recruited through word-of-mouth among family members of the patient group and through secondary education institutions offering primary education programs for adults in rural areas.

All tests were administered individually in quiet, well-lit rooms. Patients and their family members were evaluated at a public hospital, whereas the remaining participants in the control group were assessed at educational institutions that granted the researchers access to their facilities. Half of the participants completed the tests individually in the following sequence: (1) the MoCA cognitive screening test; (2) the TMT-B; (3) the STROOP Color and Word Test; (4) the Hopkins Verbal Learning Test (HVLT-R); and (5) Digit Span Forward and Backward subtests of the WAIS-IV. The remaining participants completed the tests in the reverse order. Assessment sessions lasted approximately 45 to 60 minutes.

Ethical Considerations

According to Article 11 of Resolution 8430 of 1993 issued by the Colombian Ministry of Health (Ministerio de Salud de Colombia, 1993), this study was classified as minimal risk because it involved the administration of neuropsychological tests during a single assessment session. As previously mentioned, the study received approval from the corresponding institutional ethics committee, and all participants signed an informed consent prior to their inclusion in the study.

The researchers ensured the protection of the participants' rights and interests in order to safeguard their well-being and the confidentiality of their data. To this end, the data were coded and stored on password-protected devices, with access restricted to the research team, thereby ensuring their confidentiality and exclusive use for the purposes of the present study. In addition, no data were transferred or disclosed to third parties.

Participants took part in the study voluntarily and were free to withdraw from the study at any time. Accordingly, the study complied with the ethical principles of the World Medical Association's Declaration of Helsinki (Manzini, 2000), which establish that participants may take part in research provided that the study has a justified preventive or diagnostic value and does not adversely affect their mental health.

Data Analysis

Descriptive statistics were calculated to characterize the level of cognitive functioning of the participant groups on the neuropsychological tests administered. Subsequently, the Shapiro-Wilk test was used to assess the normality of the continuous variables. Based on the results, either Student's t test or the Mann-Whitney U test for independent samples was used to compare the performance of the patient and healthy control groups on the neuropsychological battery administered in this study. Finally, a binary logistic regression model was calculated to determine the probability that patients with stage 1 or stage 2 CKD would exhibit cognitive impairment, based on the tests administered.

The linear relationship between the independent variables and the logit of the dependent variable was assessed using the Box-Tidwell test (Box & Tidwell, 1962), and model fit was estimated using the Nage-lkerke statistic (Thompson et al., 2003). The specificity and sensitivity of each test were calculated using roc curve analysis. All analyses were performed using SPSS Statistics, version 25 (IBM, 2017), with a p value of .05.

Results

With respect to the sociodemographic characteristics, the mean age of both groups was 51 years (SD = 7.00); 70% were female, 96.7% lived in Valle del Cauca, 78.3% resided in rural areas, and 70% of all participants reported belonging to socioeconomic stratum 1. Regarding educational attainment, 26% had completed up to the second year of schooling, and 56.7% reported having completed five years of education. Although the groups were matched for age, sex, and educational attainment, greater heterogeneity was observed in the socioeconomic stratum of the control group, which included participants from strata 3 and 5, categories that were not represented in the patient group. This aspect was taken into consideration in the subsequent interpretation of the results. Table 1 presents the sociodemographic characteristics of both participant groups in greater detail.

Table 1. Sociodemographic Characteristics of the Two Participant Groups

Note. Source: Prepared by the authors.

Regarding participants' performance on the neuropsychological tests administered, their profile was similar to that of the control group (see Table 2). As expected, the overall MoCA score suggested possible cognitive impairment in most participants, specifically in 29 patients and 20 controls. On the remaining tests, between 10% and 50% of participants scored below the expected range according to the scoring and interpretation guidelines based on normative data for the Colombian population.

Table 2. Neuropsychological Tests Administered

Note.^a Independent-samples t test. For all other comparisons, the Mann-Whitney U test was used. Source: Prepared by the authors

As shown in Table 2, the two participant groups differed significantly on two measures: the MoCA abstraction subtest (p=.025, d=-.27) and TMT-B completion time (p=.002, d=-.70). In both cases, the patient group performed more poorly than the control group. The effect size for the abstraction subtest was small, whereas the effect size for TMT-B completion time was moderate to large, indicating clinically relevant cognitive slowing in the patient group.

No statistically significant differences were observed for the remaining measures; however, the effect sizes suggested trends toward poorer performance in visuospatial/executive functioning (d=-0.26), delayed memory (d = -0.20), and the STROOP interference task (d = -0.27). All other comparisons yielded trivial effect sizes (d < .20), indicating similar performance between groups. Overall, these findings suggest a mild pattern of impairment in processing speed and abstract reasoning among patients with early-stage CKD, which was more evident on tasks requiring executive control and cognitive flexibility.

The two measures that showed significant differences between the groups (abstraction and TMT-b completion time), together with age and the total scores on the remaining tests administered, were entered as independent variables into a binary logistic regression model to evaluate their ability to predict cognitive impairment among patients with stage 1 or stage 2 CKD.

To this end, the linearity of the continuous variables with respect to the logit of the dependent variable was assessed using the Box-Tidwell procedure (Box & Tidwell , 1962). In addition, a Bonferroni correction was applied using the four terms included in the model, resulting in an accepted level of statistical significance of p < .0125 (Tabachnick & Fidell, 2014). Based on this assessment, all continuous independent variables were found to be linearly related to the logit of the dependent variable. It should be noted that several models were calculated to evaluate the neuropsychological tests used in this study according to the cognitive domains that the international literature has reported to be commonly affected during the early stages of CKD.

The final logistic regression model, consisting of three predictor variables—the MoCA abstraction subtest, TMT-B completion time, and STROOP interference—was statistically significant, χ² 4) = 18, p = .01. The model explained 34.6% of the variance in cognitive impairment (Nagelkerke R2) and correctly classified 68.3% of the cases.

In addition, sensitivity was 63.3%, specificity was 73.3%, the positive predictive value was 70.4%, and the negative predictive value was 66.7% (see Figure 1). Given the sample size, this regression model should be considered exploratory in nature.

Overall, the model preliminarily suggests that longer TMT-B completion times were associated with a greater probability of cognitive impairment among patients with stage 1 or stage 2 CKD (1.02). Meanwhile, lower scores on the MoCA abstraction subtest (3.18), as well as lower STROOP interference scores (1.06), were associated with a greater probability of cognitive impairment among patients with stage 1 or stage 2 CKD (see Table 3).

Figure 1. Roc Curve

As shown in Figure 1, the area under the ROC curve was 0.787 (95% ci: 0.674-0.899), indicating acceptable discriminative ability in this specific sample (Hosmer et al., 2013).

Table 3. Binary Logistic Regression

Note. Prepared by the authors

Discussion

The main contribution of this study was to explore, in a sample of patients with early-stage CKD and low educational attainment, which brief and easily administered neuropsychological tests showed the greatest discriminative ability in this population, thereby providing preliminary evidence regarding their potential utility as screening tools. This finding suggests that these patients may exhibit subtle cognitive differences that are not always evident in routine clinical practice and may require more sensitive assessment procedures for their detection.

Specifically, the findings indicate that, during the early stages of CKD, patients' cognitive performance did not differ significantly from that of the control group across most cognitive domains, although trends toward poorer performance were observed on tasks assessing cognitive flexibility and processing speed. Given the limited sample size and the cross-sectional nature of the study, these differences should be interpreted as trends observed in this sample rather than as conclusive evidence of incipient cognitive impairment. Nevertheless, this observed trend is consistent with the findings of the systematic reviews conducted by Berger et al. (2016), Brodski et al. (2018), and Tian et al. (2019), which found that patients in the early-stage CKD tend to experience difficulties in processing speed.

The poorer performance on the two tests that showed significant differences between the patient and control groups may indicate alterations in white matter integrity and reductions in the volume of frontal-predominant cortico-subcortical brain structures, as these are the neural networks that must be activated to regulate attention and processing speed during the TMT-B and to facilitate verbal reasoning processes (Bos et al., 2018; Carbone et al., 2023; Soto-Añari et al., 2018). These are also the neural networks that have been associated with inhibitory performance on the STROOP test, a measure that, although it did not reach the predetermined level of statistical significance in the between-group comparisons, was significant in the prediction model.

On the other hand, no significant differences were found in this study in attention or short-term memory, as reported in the aforementioned systematic reviews of patients with early-stage CKD. One possible explanation is that the tests used activate cortical brain networks in posterior associative areas, such as the temporoparieto-occipital region, which may exhibit some degree of compensation during the early stages of the disease, thereby providing patients with a greater capacity to withstand neurological alterations than fronto-subcortical regions, where the earliest signs of CKD-related neuropsychological impairment have been suggested to occur. However, this hypothesis requires empirical verification.

Indeed, greater frontal cortico-subcortical involvement would be consistent with findings on one of the most common causes of mild cognitive impairment in middle-aged and older adults (Jia et al., 2014). These findings are consistent with studies indicating greater vulnerability of frontal networks to various sources of neurological damage, including metabolic diseases such as CKD, which does not usually directly affect the central nervous system. The findings also suggest that individuals with low educational attainment tend to obtain lower scores on neuropsychological tests, particularly when these tests rely on knowledge acquired through formal schooling.

On the other hand, it should also be noted that the groups differed to some extent in their socioeconomic stratum distribution. Although most participants belonged to socioeconomic strata 1 and 2, the control group included several individuals from higher socioeconomic strata. Previous studies (Jia et al., 2014; Larnyo et al., 2022) have shown that socioeconomic status may be associated with educational opportunities, cognitive stimulation, and access to healthcare resources, all of which may influence cognitive performance independently of the presence of CKD. Consequently, it cannot be ruled out that some of the observed differences reflect the combined influence of socioeconomic and educational factors.

According to some authors, both living in rural areas and engaging in unskilled occupations have been associated with poorer cognitive performance, particularly in samples of older adults in whom cognitive impairment is suspected to affect quality of life (Feger et al., 2020; Jia et al., 2014; Soto-Añari et al., 2018). In this regard, a similar pattern was observed in the present study, as more than half of the participants scored below the expected range on the MoCA screening test, and between 30% and 50% obtained scores at or below the 25th percentile on the remaining tests administered. These findings may suggest that, in contexts of low educational attainment, performance on neuropsychological tests may be influenced by educational factors; however, this is not sufficient to attribute such performance to neurological damage. Likewise, the findings suggest that low educational attainment and a rural context may affect performance on screening tests, even when they include adjustments for educational attainment. To confirm this, studies such as the present one, in which educational attainment and age are controlled for, are needed to determine whether participants exhibit a performance profile different from that expected.

Finally, it is worth noting that two tests assessing processing speed (TMT-B completion time and STROOP interference) and one assessing verbal reasoning (the MoCA abstraction subtest) showed the greatest discriminative ability in this sample of patients with stage 1 or stage 2 CKD and low educational attainment. The model correctly classified 68.3% of the cases in this sample, suggesting moderate discriminative ability that warrants validation in future studies.

Furthermore, this model explained 34.6% of the variance, which is generally considered a reasonable level of explanatory power for studies involving cognitive measures. Nevertheless, this finding should be interpreted as preliminary given the sample size, particularly considering that patients have a metabolic disease that does not directly affect the central nervous system but rather is a systemic condition that affects the entire body, including neurological functioning.

In conclusion, the findings suggest that a brief battery composed of these tests may be useful for guiding cognitive screening in patients with early-stage CKD and low educational attainment. This hypothesis should be confirmed in future studies.

Lastly, it is important to acknowledge that this study has several limitations, including the sample size, the absence of longitudinal follow-up, and the limited control of certain clinical variables. Furthermore, although the tests used are supported by Colombian normative data adjusted for educational attainment, these norms may not fully reflect the sociocultural characteristics of rural populations with very low educational attainment.

This limitation is further compounded by the fact that the groups were not fully equivalent with respect to socioeconomic stratum and rural residence. Future studies should replicate these findings using larger samples and longitudinal designs, while incorporating clinical indicators of CKD and greater sociodemographic diversity to enhance the generalizability of the results and support the development of more sensitive and culturally appropriate screening protocols.

References

Arango-Lasprilla, J. C., Rivera, D., y Usuga, D. R. (2022). Neuropsicología en Colombia: Datos normativos, estado actual y retos a futuro. Manual Moderno.

Arnold, R., Issar, T., Krishnan, A. V., y Pussell, B. A. (2016). Neurological complications in chronic kidney disease. Journal of the Royal Society of Medicine Cardiovascular Disease, 5, 1-13. https://doi.org/10.1177/2048004016677687

Ato, M., López, J. J., y Benavente, A. (2013). Un sistema de clasificación de los diseños de investigación en psicología. Anales de Psicología, 29(3), 1038-1059. https://dx.doi.org/10.6018/analesps.293.178511

Benedict, R. H., Schretlen, D., Groninger, L., y Brandt, J. (1998). Hopkins Verbal Learning Test-Revised: Norma­tive data and analysis of inter-form and test-retest reliability. The Clinical Neuropsychologist, 12(1), 43-55. https://doi.org/10.1076/clin.12.1.43.1726

Berger, I., Wu, S., Masson, P., Kelly, P. J., Duthie, F. A., Whiteley, W., Parker, D., Gillespie, D., y Webster, A. C. (2016). Cognition in chronic kidney disease: a systematic review and meta-analysis. BMC Medicine, 14, 206. https://doi.org/10.1186/s12916-016-0745-9

Bos, D., Wolters, F. J., Darweesh, S. K., Vernooij, M. W., de Wolf, F., Ikram, M. A., y Hofman, A. (2018). Cerebral small vessel disease and the risk of Dementia: A systematic review and meta-analysis of population-based evidence. Alzheimer's & Dementia, 14(11), 1482-1492. https://doi.org/10.1016/j.jalz.2018.04.007

Box, G. E. P, y Tidwell, P. W. (1962). Transformation of the independent variables. Technometrics, 4(4), 531-550. https://doi.org/10.1080/00401706.1962.10490038

Brandt, J. (1991). The Hopkins Verbal Learning Test: Development of a new memory test with six equivalent forms. The clinical neuropsychologist, 5(2), 125-142. https://doi.org/10.1080/13854049108403297

Brickman, A. M., Cabo, R., y Manly, J. J. (2006). Ethical issues in cross-cultural neuropsychology. Applied Neuropsychology, 13(2), 91-100. https://doi.org/10.1207/s15324826an1302_4

Brodski, J., Rossell, S. L., Castle, D. J., y Tan, E. J. (2018). A systematic review of cognitive impairments associated with kidney failure in adults before natural age-related changes. Journal of the International Neuropsychological Society, 25(1), 101-114. https://doi.org/10.1017/S1355617718000917

Carbone, C., Balboni, E., Beltrami, D., Gasparini, F., Vinceti, G., Gallingani, C., Salvatori, D., Salemme, S., Molinari, M. A., Tondelli, M., Marti, A., Chiari, A. L., y Zamboni, G. (2023). Neuroanatomical Correlates of Cognitive Tests in Young-onset MCI. Journal of Integrative Neuroscience, 22(6), 152. https://doi.org/10.31083/j.jin2206152

Crowe, K., Quinn, T. J., Mark, P. B., y Findlay, M. D. (2021). "Is It Removed During Dialysis?"—Cognitive Dysfunc­tion in Advanced Kidney Failure—A Review Article. Frontiers in Neurology, 12, 787370. https://doi.org/10.3389/fneur.2021.787370

Delgado, C., Araneda, A., y Behrens, M. I. (2019). Validation of the Spanish-language version of the Montreal Cognitive Assessment test in adults older than 60 years. Neurología (English Edition), 34(6), 376-385. https://doi.org/10.1016/j.nrleng.2018.12.008

Drake, M. A. (2007). Evaluación de la atención. En D. I. Burin, M. A. Drake y P Harris (Comps.), Evaluación neuropsicológica en adultos (pp. 129-161). Paidós.

Drew, D. A., Weiner, D. E., y Sarnak, M. J. (2019). Cognitive impairment in CKD: Pathophysiology, management, and prevention. American Journal of Kidney Diseases: The Official Journal of the National Kidney Foundation, 74(6), 782-790. https://doi.org/10.1053/j.ajkd.2019.05.017

Duarte, A., Gómez, L., Aguirre, D., y Pineda, D. (2006). Caracterización neuropsicológica de los pacientes adultos en diálisis de una institución especializada de Medellín-Colombia. Universitas Psychologica, 5(3), 627-646. http://hdl.handle.net/10554/33168

Faria, A. L., Pinho, M. S. y Bermúdez i Badia, S. (2020). A comparison of two personalization and adaptive cog­nitive rehabilitation approaches: a randomized controlled trial with chronic stroke patients. Journal of Neuro Engineering Rehabilitation, 17, 78. https://doi.org/10.1186/s12984-020-00691-5

Feger, D. M., Willis, S. L., Thomas, K. R., Marsiske, M., Rebok, G. W., Felix, C., y Gross, A. L. (2020). Incident instru­mental activities of daily living difficulty in older adults: Which comes first? Findings from the advanced cognitive training for independent and vital elderly study. Frontiers in Neurology, 11, 550577. https://doi.org/10.3389/fneur.2020.550577

Fraser, C. L., y Arieff, A. I. (1988). Nervous system complications in uremia. Annals of internal medicine, 109(2), 143­153. https://doi.org/10.7326/0003-4819-109-2-143

Golden, C. J. (2020/1994). Stroop. Test de Colores y Palabras (B. Ruiz-Fernández, T. Luque y F. Sánchez-Sánchez, Eds.). TEA Ediciones.

Harhay, M. N., Xie, D., Zhang, X., Hsu, C. Y., Vittinghoff, E., Go, A. S., Sozio, M., Blumenthal, J., Seliger, S., Chen, J., Deo, R., Dobre, M., Akkina, S., Reese, P. P, Lash, J. P, Yaffe, K., Tamura, M. K., Appel, L. J., Feldman, H. I., y Rahman, M. (2018). Cognitive impairment in non-dialysis-dependent CKD and the transition to dialysis: findings from the chronic renal insufficiency cohort (CRIC) study. American Journal of Kidney Diseases, 72(4), 499-508. https://doi.org/10.1053/j.ajkd.2018.02.361

Hosmer, D. W., Jr., Lemeshow, S., y Sturdivant, R. X. (2013). Applied logistic regression (3.^a ed.) Wiley.

IBM Corporation Released. (2017). IBM SPSS Statistics for Windows (Version 25.0) [Programa de ordenador]. IBM Corp.

Jia, J., Wang, F., Wei, C., Zhou, A., Jia, X., Li, F., Tang, M., Chu, L., Zhou, Y., Zhou, C., Cui, Y., Wang, Q., Wang, W., Yin, P, Hu, N., Zuo, X., Song, H., Qin, W., Wu, L., y Dong, X. (2014). The prevalence of dementia in urban and rural areas of China. Alzheimer's & dementia, 10(1), 1-9. https://doi.org/10.1016/j.jalz.2013.01.012

Joseph, S. J., Bhandari, S. S., y Dutta, S. (2019). Cognitive impairment and its correlates in chronic kidney disease patients undergoing haemodialysis. Journal of Evolution of Medical and Dental Sciences, 8(36), 2818-2822. https://doi.org/10.14260/jemds/2019/611

Karakizlis, H., Thiele, S., Greene, B., y Hoyer, J. (2021). Cognitive performance in dialysis patients- "when is the right time to test?". BMC Nephrology, 22(1), 1-10. https://doi.org/10.1186/s12882-021-02333-x

Kimmel, P L., Thamer, M., Richard, C. M., y Ray, N. F. (1998). Psychiatric illness in patients with end-stage renal disease. The American Journal of Medicine, 105(3), 214-221. https://doi.org/10.1016/S0002-9343(98)00245-9

Larnyo, E., Dai, B., Nutakor, J. A., Ampon-Wireko, S., Larnyo, A., & Appiah, R. (2022). Examining the impact of socioeconomic status, demographic characteristics, lifestyle and other risk factors on adults' cognitive functioning in developing countries: an analysis of five selected WHO SAGE Wave 1 Countries. International journal for equity in health, 21(1), 31. https://doi.org/10.1186/s12939-022-01622-7

Manzini, J. L. (2000). Declaración de Helsinki: principios éticos para la investigación médica con participantes humanos. Acta bioethica, 6(2), 321-334. https://www.wma.net/es/policies-post/declaracion-de-helsin-ki-de-la-amm-principios-eticos-para-las-investigaciones-medicas-en-seres-humanos/

Ministerio de Salud de Colombia. (1993, octubre 4). Resolución 8430 de 1993. Por la cual se establecen las normas científicas, técnicas y administrativas para la investigación en salud. https://www.minsalud.gov.co/sites/rid/lists/bibliotecadigital/ride/de/dij/resolucion-8430-de-1993.pdf

Murthy, V. S., y Shukla, V. S. (2020). A study of executive function in patients with chronic kidney disease before and after a single session of hemodialysis. Journal of Neurosciences in Rural Practice, 11(2), 250-255. https://doi.org/10.1055/s-0040-1703961

National Kidney Foundation. (2012). KDOQI clinical practice guideline for diabetes and CKD: 2012 update. Ame­rican Journal of Kidney Diseases, 60(5), 850-886. https://doi.org/10.1053/j.ajkd.2012.07.005

Owolabi, L. F., Abdu, A., Ibrahim, A., Owolabi, D. S., Nalado, A., Bappa, A., y Taura, A. A. (2016). Related factors and predictors of cognitive dysfunction in chronic kidney disease on maintenance hemodialysis in Nige­ria. Journal of Neurosciences in Rural Practice, 7(S1), S062-S067. https://doi.org/10.4103/0976-3147.196433

Pedraza, O. L., Salazar, A. M., Sierra, F. A., Soler, D., Castro, J., Castillo, P, Hernández, C., y Piñeros, C. (2016). Confiabilidad, validez de criterio y discriminante del Montreal Cognitive Assessment (MoCA) test, en un grupo de adultos de Bogotá. Acta Médica Colombiana, 41(4), 221-228. https://www.redalyc.org/articulo.oa?id=163149123004

Pereira-Manrique, F., y Reyes, M. F. (2013). Confiabilidad y validez del test Montreal Cognitive Assessment(MoCA) en población mayor de Bogotá, Colombia. Revista Neuropsicología, Neuropsiquiatria y Neurociencias, 13(2), 39-61. https://revistaneurociencias.com/index.php/RNNN/article/view/335/276

Pi, H.-C., Xu, Y.-F., Xu, R., Yang, Z.-K., Qu, Z., Chen, Y.-Q., Liu, G.-L., y Dong, J. (2016). Cognitive impairment and structural neuroimaging abnormalities among patients with chronic kidney disease. Kidney and Blood Pressure Research, 41(6), 986-996. https://doi.org/10.1159/000452603

Reitan, R. M. (1958). Validity of the Trail Making Test as an Indicator of Organic Brain Damage. Perceptual and Motor Skills, 8(3), 271-276. https://doi.org/10.2466/pms.1958.8.3.271

Roebuck-Spencer, T. M., Glen, T., Puente, A. E., Denney, R. L., Ruff, R. M., Hostetter, G., y Bianchini, K. J. (2017). Cognitive screening tests versus comprehensive neuropsychological test batteries: A national academy of neuropsychology education paper. Archives of Clinical Neuropsychology: The Official Journal of the National Academy of Neuropsychologists, 32(4), 491-498. https://doi.org/10.1093/arclin/acx021

Rosas, R., Tenorio, M., Pizarro, M., Cumsille, P, Bosch, A., Arancibia, S., Carmona-Halty, M., Pérez-Salas, C. P., Pino, E., Vizcarra, B., y Zapata-Sepúlveda, P. (2014). Estandarización de la Escala Wechsler de Inteligencia Para Adultos: Cuarta Edición en Chile. Psykhe, 23(1), 1-18. https://dx.doi.org/10.7764/psykhe.23.l529

Rossetti, H. C., Lacritz, L. H., Cullum, C. M., y Weiner, M. F. (2011). Normative data for the Montreal Cognitive Assessment (MoCA) in a population-based sample. Neurology, 77(13), 1272-1275. https://doi.org/10.1212/WNL.0b013e318230208a

Sagubay, D. J. Á., Macas, J. T., y Celleri, W. P. (2017). Deterioro cognitivo en pacientes con hemodiálisis. Medicina, 21(1), 27-33. https://doi.org/10.23878/medicina.v21i1.759

Soto-Añari, M., López, N., Aquino-Ayala, R., Denegri-Solís, L., Belón-Hercilla, V., Ferrel-Ortega, F.-R., Caldichoury, N., y Hernández-Chamorro, J. (2018). Afectación Neuropsicológica de la Función Ejecutiva en Pacientes con Insuficiencia Renal Crónica. Revista CES Psicología, 11(2), 78-87. https://doi.org/10.21615/cesp.11.27

Tabachnick, B. G., y Fidell, L. S. (2014). Using multivariate statistics (6.^a ed.). Pearson.

Tanaka, S., y Okusa, M. D. (2020). Crosstalk between the nervous system and the kidney. Kidney International, 97(3), 466-476. https://doi.org/10.1016/j.kint.2019.10.032

Tian, X., Guo, X., Xia, X., Yu, H., Li, X., y Jiang, A. (2019). The comparison of cognitive function and risk of demen­tia in CKD patients under peritoneal dialysis and hemodialysis: A PRISMA-compliant systematic review and meta-analysis: A PRISMA-compliant systematic review and meta-analysis. Medicine, 98(6), e14390. https://doi.org/10.1097/md.0000000000014390

Thompson, W. K., Xie, M., y White, H. R. (2003). Transformations of covariates for longitudinal data. Biostatistics, 4(3), 353-364. https://doi.org/10.1093/biostatistics/43.353

Wechsler, D. (2014). WAIS-IV, Escala Weschlerde inteligencia para adultos-IV (Trad.: M. C. Uribe Ferrari). Manual Moderno.

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