|Year : 2018 | Volume
| Issue : 3 | Page : 184-190
A study comparing cognitive function assessment in type-2 diabetes mellitus using Rowland Universal Dementia Assessment Scale and Mini Mental State Examination
S Shanmugapriya1, N Dhandapani2, T Saravanan2
1 Department of Pharmacology, PSG Institute of Medical Sciences and Research, Coimbatore, Tamil Nadu, India
2 Department of Medicine, PSG Institute of Medical Sciences and Research, Coimbatore, Tamil Nadu, India
|Date of Web Publication||20-Jul-2018|
Dr. S Shanmugapriya
Department of Pharmacology, PSG Institute of Medical Sciences and Research, Off Avinashi Road, Peelamedu, Coimbatore - 641 004, Tamil Nadu
Source of Support: None, Conflict of Interest: None
BACKGROUND: Diabetes mellitus is a metabolic disorder which can predispose to cognitive impairment. It is important to screen diabetic patients for cognitive dysfunction in the routine clinical management. Our study aimed at comparative evaluation of commonly used cognition assessment tools such as Mini Mental State Examination (MMSE) and Rowland Universal Dementia Assessment Scale (RUDAS) in diabetes patients.
METHODS: The study was conducted as a prospective case–control design in a tertiary care teaching hospital from March to October 2015. After obtaining written informed consent, the data on demographic details, duration of diabetes, and glycemic control marked by glycated hemoglobin were recorded. A total of 101 previously diagnosed type-2 diabetes patients and an equal number of age-, gender-, and literacy-matched controls without diabetes were administered the MMSE and RUDAS cognition scales in a one-to-one interview by a trained diabetic educator who was blinded to the groups.
RESULTS: The study revealed that there was a significant difference in cognition scores between the diabetic patients with short duration (<5 years) and those with a longer history of diabetes (≥5 years) only in the MMSE scale using independent sample t-test (P = 0.018), unlike the RUDAS in which the difference was insignificant (P = 0.235). Similarly, there was also a significant correlation between glycemic control and cognition scores in the MMSE (P = 0.03), but not in the RUDAS scale (P = 0.083).
CONCLUSION: MMSE scale has been proved to be advantageous over the RUDAS as a screening tool for cognition assessment in diabetes patients.
Keywords: Cognition score, diabetes duration, glycemic control, screening
|How to cite this article:|
Shanmugapriya S, Dhandapani N, Saravanan T. A study comparing cognitive function assessment in type-2 diabetes mellitus using Rowland Universal Dementia Assessment Scale and Mini Mental State Examination. Int J Health Allied Sci 2018;7:184-90
|How to cite this URL:|
Shanmugapriya S, Dhandapani N, Saravanan T. A study comparing cognitive function assessment in type-2 diabetes mellitus using Rowland Universal Dementia Assessment Scale and Mini Mental State Examination. Int J Health Allied Sci [serial online] 2018 [cited 2022 Jul 2];7:184-90. Available from: https://www.ijhas.in/text.asp?2018/7/3/184/237267
| Introduction|| |
Diabetes mellitus is a metabolic disorder due to dysregulation of glucose homeostasis. The world prevalence of diabetes in adults has been predicted to increase from 285 million in 2010 to 439 million by 2030. It is well established that diabetes is associated with significant morbidity, including neurological disability. Although it is known that diabetes can lead to cognitive deficits in the long term, elucidation of the effects on the central nervous system is still incomplete, unlike other complications such as nephropathy, retinopathy, and peripheral neuropathy. It is estimated that in 2010, 35.6 million people lived with dementia worldwide, with numbers expected to almost double every 20 years, to 65.7 million by 2030 and 115.4 million by 2050. In addition to this, the scenario of type-2 diabetes predisposing to and accelerating cognitive impairment would further increase the burden of disease. With increasing prevalence of type-2 diabetes in India, the magnitude of cognitive impairment that the disease contributes to and the factors affecting should be studied.
Studies from various populations have consistently shown that diabetes is associated with cognitive deficits and dementia; both in elderly and younger patients. Various pathophysiological mechanisms have been proposed. A process similar to that of peripheral neuropathy such as alterations in Na + K + ATPase activity and the ensuing reduction in myoinositol and sorbitol metabolism has been suggested. These may trigger biochemical abnormalities at the neuronal level, resulting in structural and functional changes, primarily in the white matter. Chronic hyperglycemia, atherosclerosis, and hemodynamic changes may lead to microinfarcts which in turn to cognitive impairment. Diabetes-induced microvascular changes, such as disruption of the blood–brain barrier, and the resultant derangement of neurovascular coupling could be partly related to cognitive dysfunction.,, Hyperglycemia may also be directly toxic to the neuron, leading to its degeneration  and consequentially the hippocampal as well as global atrophy. Thus, diabetes is considered as one of the important contributory factors in the development of cognitive deficits.
Undiagnosed cognitive impairment can lead to reduced health status, implying that screening for cognitive deficits should be an integral part of patient management in diabetes. Among the neuropsychological tests for dementia, the Mini Mental State Examination (MMSE), devised by Folstein et al., is one of the most widely used tools for the assessment of cognitive impairment. The Rowland Universal Dementia Assessment Scale (RUDAS) is yet another screening test, designed as a multicultural cognitive assessment scale relatively unaffected by gender, education, and first language, as it can easily be converted for implementation in the local community. Although there are studies comparing the accuracy and reliability of these two scales in geriatric population with and without dementia,,,, a thorough literature review reveals a paucity of studies directly comparing the two in a diabetic population. Hence, our study aimed at evaluating the effectiveness of the two scales as tools in assessing the cognitive decline in type-2 diabetes patients by comparing the correlation of cognitive score with the glycemic control and duration of diabetes.
| Methods|| |
This was a single-center, hospital-based case–control study conducted by collecting data from study participants from March to October 2015. Approval from the Institutional Human Ethics Committee was obtained before the start of the study.
All patients willing to give consent, both males and females aged between 30 and 60 years with previously diagnosed type-2 diabetes mellitus (case) and without diabetes mellitus (control), with or without hypertension were included for the study.
Patients with type-1 diabetes, stroke, alcohol intake or smoking habits, total blindness in both eyes, or complete loss of hearing in both ears; and patients who were previously diagnosed with and were known case of mental retardation, psychiatric disorders, and psychoactive drug use in addition to pregnant and lactating women were excluded.
The sample size calculation was done using “Epi tools,” with a prevalence of 7% which was based on the previous data, and desired precision of 0.05 at 95% confidence interval revealed the sample size estimate of 101.
After obtaining written informed consent, the data on age, sex, literacy, current fasting and postprandial blood glucose (done by enzymatic reference method with hexokinase), and glycated hemoglobin (HbA1c) values (done by immunoturbidimetry), along with history on duration of diabetes and duration of hypertension were collected. The study was conducted on a sample of 101 diabetic cases and 101 non-diabetic controls matched for age, sex, and literacy to ensure homogeneity of the sample and to avoid bias in the results, owing to these parameters. In this study, patients who exhibited the ability to both read and write the colloquial language and/or English were included as literates.
MMSE and RUDAS scales were administered in a one-to-one interview with the study participant by a trained diabetic educator who was blinded to the group to which the patient belonged to. MMSE tested global cognition function with items assessing orientation, word recall, registration, attention, language abilities, and visuospatial ability and was scored out of 30. As per the MMSE scale, 21–23, 11–20, and ≤10 scores were indicative of mild, moderate, and severe cognitive dysfunction, respectively, while a score of 24 or higher was considered normal. According to the recommendations of Crum et al., the MMSE scores were corrected for the literacy status. Based on these criteria, a score <24 was considered as impaired cognition for literates and that <22 for illiterates. RUDAS scale measured memory, gnosis, praxis, visuospatial skills, judgment, and language. The maximum RUDAS score was 30, for which the recommended cut point ≤22 was used to indicate cognitive impairment.
Statistical analyses was done using Pearson's correlation test to analyze the correlation between mean MMSE/RUDAS score with parameters such as duration of diabetes and glycemic control. Student's t-test was used to identify significant difference in the mean scores between cases and controls based on age, sex, literacy, and comorbidity.
| Results|| |
The data were entered into Excel and analyzed using SPSS version 19. Among 101 cases, 4% had mild and 1% had moderate cognitive dysfunction using MMSE, whereas cognition deficit was identified in 5% cases using RUDAS. 1% controls, according to RUDAS score, had cognitive impairment while MMSE scoring revealed that 3% controls had cognitive dysfunction which was mild.
The baseline characteristics of age, sex, and literacy in both groups were matched [Table 1]. There were a higher proportion of females in both the case and the control group, with a male to female ratio of 36:65. Percentage of literates was high (94%) in both groups. The cases were arbitrarily categorized based on the observed HbA1c value as those with good control and poor control. An HbA1c value of 8.5% was taken as the cutoff value; those with <8.5% were included in the good control group and those with HbA1c values ≥8.5% were grouped as poor controllers of glycemic level. 44.6% of cases had good control, while 54.4% were included in the poor control group. The mean score was found to be less in patients who had HbA1c level ≥8.5% using both the scales. An independent sample t-test showed that the mean difference between the scores of patients with good and poor control was statistically significant in MMSE scale (P = 0.046), while in RUDAS scale, the mean difference was not statistically significant (P = 0.372) [Figure 1].
|Figure 1: Association between mean cognition score expressed as mean ± standard deviation and glycated hemoglobin (glycemic control) using Mini Mental State Examination and Rowland Universal Dementia Assessment Scale|
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Cases in our study population were divided into those with duration of diabetes <5 years and those with ≥5 years history of diabetes. Accordingly, it was found that 60.4% cases had <5 years of diabetes history and the rest had ≥5 years duration. The mean scores were found to be less in people who had diabetes ≥5 years using both scales and was statistically significant in MMSE scale (P = 0.018) but not in RUDAS scale (P = 0.235) [Figure 2]. Furthermore, using Pearson's correlation test, a statistically significant negative correlation between duration of diabetes and cognitive levels (P = 0.015) in addition to a significant positive correlation between glycemic control and cognitive score (P = 0.03) was detected in testing with MMSE scale in the diabetes patients. In contrast, no significant correlation between duration of diabetes or glycemic control with cognitive dysfunction was evident while using RUDAS scale [Table 2].
|Figure 2: Association between mean cognition score expressed as mean ± standard deviation and duration of diabetes using Mini Mental State Examination and Rowland Universal Dementia Assessment Scale|
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|Table 2: Correlation of duration of diabetes and glycemic control with cognitive levels using Mini Mental State Examination and Rowland Universal Dementia Assessment Scale|
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In both MMSE and RUDAS scales, an independent sample t-test revealed that there was no statistically significant difference between the cases and controls in both categories of <50 years of age and those with ≥50 years. The difference in cognition level between the cases and controls in the two gender groups was similarly tested using independent sample t-tests, and it was found that there was no statistically significant difference in the mean scores based on gender using either of the scales [Table 3]. Another significant observation was that the mean score of females, in both cases and controls, were lower than that of males, even though the difference was not statistically significant, except in the diabetic group assessed using RUDAS scale, wherein the mean score of females was significantly higher than that of males [Figure 3].
|Table 3: Independent sample t-test for comparing the mean scores of cases and controls across age and gender groups using Mini Mental State Examination and Rowland Universal Dementia Assessment Scale|
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|Figure 3: Comparison of mean cognition score expressed as mean ± standard deviation between males and females using Mini Mental State Examination and Rowland Universal Dementia Assessment Scale|
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It was found using Student's t-test that the illiterates had a mean score lower than that of the literates, though a statistically significant difference was observed only with the MMSE scale (P = 0.001) but not in the RUDAS scale (P = 0.085). Ninety-five percent of the study population were literates, and this precluded performing a between-group analysis for cases and controls [Figure 4].
|Figure 4: Association between cognition level and literacy using Mini Mental State Examination and Rowland Universal Dementia Assessment Scale|
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An independent sample t-test revealed that there was no statistically significant difference between the mean scores of cases and controls with hypertension. Similarly, there was no statistically significant difference between the mean scores of those with diabetes alone and those with diabetes and hypertension in the case group using both MMSE and RUDAS [Table 4], indicating that coexisting hypertension did not significantly affect cognition score in patients with type-2 diabetes.
|Table 4: Independent sample t-test for comparing the difference in mean cognition scores in those with and without hypertension using Mini Mental State Examination and Rowland Universal Dementia Assessment Scale|
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| Discussion|| |
The MMSE is a cognitive scale used for detecting cognitive impairment. Having developed in the West, it has serious limitations due to cultural and educational bias., It is one of the commonly used tools for cognitive assessment consisting of 11-item testing with sensitivity of 87% and specificity of 82%. The RUDAS is a newer screening test developed in Australia. It is a brief six-item screening test which is short and easy to administer. It is claimed to be culturally and educationally unbiased and developed in view of application in multicultural setting.,, It assesses body orientation, praxis, drawing, judgment, memory, and language. It has the additional advantage of being capable of assessing the impairment in executive function. With a cutoff score of 23/30, it has 88% sensitivity and 90% specificity.,
It has been well proven that age, in addition to ethnicity and education, is an important factor affecting the MMSE score. In our study, there was no statistically significant difference in the mean score between patients aged above and below 50 years. In a study done using MMSE scale, there was no quantitative difference in cognition scores above and below 70 years of age, but a significant difference between diabetic and non-diabetic patients was detected. Their result indicated that in diabetic patients, diabetes could be a greater risk factor for cognitive impairment than age. However, our study results did not replicate such a significant difference between cases and controls in both the age groups studied [Table 3]. The reason attributable to this inference is that most of the earlier studies were done in a population with higher mean age,, but our study included a much younger population and that may also account for the lower percentage of cognitive deficits detected. A similar result has been demonstrated in a study with middle-aged diabetic population.
The prevalence of diabetes is higher in men than women, but there are more women with diabetes than men. In our study sample, the proportion of females was much higher than the males. Using MMSE, the males scored higher than females though not statistically significant and this was in concordance with earlier studies. Assessed using RUDAS, the female cases scored significantly higher than male cases, but such an observation was not seen in the control group and the reason for the result could not be explained.
Our study demonstrated that the magnitude of the difference in the mean score between literates and illiterates was significantly higher in the MMSE score as compared to the RUDAS scale, indicating that our study has also proven that RUDAS scale is free of educational barrier as described in the previous studies., However, former studies done in Thailand and South Indian Malayalam population showed that cultural, linguistic, and education barriers were not fully overcome with the use of RUDAS scale.,
The cutoff values for glycemic control and duration of diabetes have been chosen arbitrarily and do not depend on the conventional cutoff adopted internationally for the management of clinical condition. The reason being that the duration of diabetes and the glycemic control beyond which cognitive dysfunction occurs, in comparison to other complications of diabetes, is less defined and less well understood. Hence, using the same clinical cutoff criteria used for management would obviously result in false-negative correlation. In the diabetic population studied, the association of mean cognition score with the glycemic control marked by HbA1c level was found to be statistically significant, in addition to a significant positive correlation which was evident only in the MMSE but not the RUDAS scale. Our study thus reflected the results obtained in few previous studies which have highlighted the positive association between poor glycemic control and poor cognition using MMSE,, but no such correlation detected using RUDAS. Another study done in middle-aged adults with type-2 diabetes has demonstrated that there is predominantly psychomotor slowing with poor metabolic control, even though learning, memory, and problem-solving skills appear to be largely intact in such patients. On the contrary, few other studies have established that the magnitude of glycemic control does not have significant correlation with the cognitive score using MMSE scale.,, The potential explanation for the contradictory results between correlations of cognitive dysfunction with glycemic control is that only the recent HbA1c values representing short-term control were included in most analyses and not the time trend in HbA1c, indicative of long-term control as the measure to categorize patients with good and bad glycemic control.
Evaluating the association between the duration of diabetes and cognitive scores revealed a significant negative correlation. Those with a longer duration (≥5 years) of diabetes exhibited a lower mean score than those with shorter duration of diabetes (<5 years) using the MMSE, but not with the RUDAS. Our results were consonant with results obtained in few similar studies.,,, Thus, most studies have proven a definitive correlation between cognitive decline and duration of diabetes than with glycemic control.
In addition, our study has shown that there was a statistically significant difference neither between the mean score of cases with and without hypertension nor between the scores of hypertensive cases and controls using both scales. Literature evidence states that although hypertension alone may not be associated with significant cognitive decline, along with diabetes, it increases the risk of cognitive impairment.
With enormously increasing prevalence of diabetes and diabetes being an important risk factor for cognitive impairment, it is the need of the hour to incorporate cognitive assessment in the routine management of diabetes patients. Ours is the first study that compared MMSE with RUDAS head-to-head in a diabetic population, and the study has proved that MMSE has a definitive advantage over RUDAS for screening diabetes-induced cognitive deficit. In patients with type-2 diabetes, increase in memory deficits with reduction in psychomotor speed and reduced executive function are strongly supported by the findings of earlier studies though there are also other cognitive domains such as verbal fluency, complex motor function, attention, and recall which are shown to be negatively affected. Hence, it is clear that diabetes indeed has composite neurocognitive effects, rather than a single one and difficulty in diagnosis of such multiple neurocognitive function deficits is well recognized. RUDAS tests the executive function unlike MMSE, yet RUDAS failed to demonstrate statistical significance which could be potentially attributed to the relatively high rate of intrasubject variability which is inherent to cognitive testing, thus impairing its ability to identify executive function deficits, especially those which are mild.
In our study, the actual differences in the mean scores between those with good and poor glycemic control (0.91) and those with shorter and longer duration of diabetes (1.11) in the MMSE were small despite achieving statistical significance. Since score differences in the range of 2–4 or greater in MMSE are necessary to conclude a clinically relevant difference, the clinical significance of our interpretation has to be guarded and requires further investigation involving a larger sample size.
Another limitation of the study is that a large proportion of participants were literates and this could be a potential source of bias in interpreting the results. Hence, we recommend that the effectiveness of MMSE scale between literates and illiterates should be compared in a diabetic population before it can be emphasized that the MMSE scale is best suited for screening cognitive deficit in routine clinical examination of diabetic patients for early identification of cognitive impairment.
| Conclusion|| |
Our study has truly delineated that cognition deficits based on MMSE scoring correlates with the magnitude of glycemic control as well as the duration of diabetes. The results signify that in the general population, screening for dementia may preferably be done with RUDAS scale, given the higher sensitivity, specificity and particularly as it is efficient to overcome the literacy barrier in a multicultural multi-linguistic population like the one in India. However, in type-2 diabetes patients, it is the MMSE scale that has been proved to be useful in detecting early cognitive impairment, especially in patients with poor glycemic control and longer history of diabetes.
Financial support and sponsorship
The study was funded by a research grant by Indian Council of Medical Research (ICMR).
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2], [Table 3], [Table 4]