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Cognitive Screening Tool in Parkinson’s Disease: Mini Mental State Examination (MMSE) Versus Montreal Cognitive Assessment (Moca)

Research Article Open Access
Arun Aggarwal2*, Maria G Bernardi1 and Lyn Wright3
1Medical Student, University of New South Wales Rural Clinical School, Coffs Harbour, Australia
2Clinical Associate Professor, Department of Neurology, Concord Hospital, Sydney, Australia
3Registered Nurse, Department of Aged Care, Coffs Harbour Health Campus, Coffs Harbour, Australia
*Corresponding authors: Arun Aggarwal
Clinical Associate Professor
Department of Neurology
Concord Hospital
Sydney, Australia
Tel: +61 2 9515 9815
Fax: +61 2 9817 6633
E-Mail: arun.a@sydney.edu.au
 
Received November 26, 2011; Published August 28, 2012
 
Citation: Aggarwal A, Bernardi MG, Wright L (2012) Cognitive Screening Tool in Parkinson’s Disease: Mini Mental State Examination (MMSE) Versus Montreal Cognitive Assessment (Moca). 1:279. doi:10.4172/scientificreports.279
 
Copyright: © 2012 Aggarwal A, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
 
Abstract
 
Background: Cognitive impairment is common in patients with Parkinson’s disease and has an impact on prognosis and quality of life. There remains a need for a brief, accurate and easily performed screening test, so that cognitive impairment can be identified reliably. The Mini Mental State Examination (MMSE) is currently the most commonly used brief screening tool however the Montreal Cognitive Assessment (MoCA) is argued to be a more suitable measure of cognitive impairment in patients with Parkinson’s disease.
 
Method: 18 patients and 11 controls were recruited from new patients and their partners attending a monthly specialist outreach Parkinson’s disease clinic in a regional centre.
 
Result: The MoCA detected more cases of mild cognitive impairment (57.1%) than the MMSE (21.4%) in patients, although it took several minutes longer to complete.
 
Conclusion: This study provides additional support for the use of the MoCA as a screening tool in clinical practice on patients with Parkinson’s disease and, for the first time, demonstrates a clear difference in MoCA and MMSE sensitivity in an Australian population. Reporting of a significant difference in test scores in a population with Parkinson’s disease is the first step towards a comprehensive validation study in the wider population.
 
Keywords
 
Parkinson’s disease; Neuropsychological tests; Cognition disorders; Screening
 
Introduction
 
Dementia and cognitive impairment are common in patients with Parkinson's disease [1] and impact on prognosis and quality of life [2-4]. Early identification is important to provide optimal drug treatment and appropriate support to patients and their carers [2-5]. Neuropsychological testing is considered to be the gold-standard for assessing cognitive impairment but this assessment is time-consuming and requires trained assessors [3-9]. Instead, the most commonly used instrument in clinical consultations is the Mini-Mental Status Examination (MMSE) [3,4]. However, the MMSE primarily assesses memory and language skills whereas then areas of cognitive impairment in patients with Parkinson’s disease primarily involve executive function, attention, verbal fluency and visuospatial skills [1,2,5]. Moreover, the MMSE has been found to be insensitive to mild and even severe forms of cognitive impairment in patients Parkinson's Disease (PD) [5-7]. As a result, two Parkinson's specific cognitive scales have been designed recently. However, they too are limited by the time required to perform them and the areas of cognitive function they assess [4].
 
There is still a need for a brief, accurate and easily performed screening test. A new cognitive scale, the Montreal Cognitive Assessment (MoCA), was designed to address some of these deficiencies and has been found to have high sensitivity and specificity for mild cognitive impairment [8]. A recent task force review of five potential scales of global cognition has recommended use of the MoCA as the most suitable measure for screening for mild cognitive impairment and dementia in clinical trials of Parkinson's disease [10]. However, further validation of the MoCA and MMSE against a more detailed neuropsychological battery has been recommended [3,9-11] and validation of these results in an Australian population is yet to be performed.
 
The aim of this research was to compare the MMSE and MoCA cognitive screening tools in patients with Parkinson's disease and controls to quantify a difference, if any, in test scores in preparation for a more comprehensive validation of the newer MoCA screening tool. It was hypothesised that there will be a significant difference between the MMSE and MoCA scores detected in patients with Parkinson’s disease and no significant difference in the controls without Parkinson’s disease.
 
Methods
 
A prospective longitudinal study took place in a regional specialist outreach Parkinson’s disease clinic held monthly over a 6-month period. Ethical approval for this study was granted by the Mid North Coast Human Research Ethics Committee. Written consent was gained from all participants before involvement.
 
Participants consisted of a convenience sample of patients newly referred to the Parkinson’s clinic and their accompanying partners as controls. All new patients were invited to participate after registering their attendance at the clinic. Patients who were non-English speaking or had severe aphasia were excluded.
 
Each participant was assessed with the MoCA and MMSE by one of two investigators (LW or MB). There was a ten minute break between assessments. Assessor and score were recorded for each participant. The first 29 participants (18 patients and 11 controls) additionally had the time taken to perform each test recorded. Participant age, sex, level of education, history of dementia, history of depression and current usage of antidepressant or anti-anxiety medication were recorded.
 
Statistical analysis was performed using PASW 18.0.2 for Windows. The cut off score for cognitive impairment was 24 or less for the MMSE [1] and 25 or less for the MoCA [8]. Outcome measures were the score and time taken to perform each test. Significance levels were set to 5% and all stated significance values are exact 2-tailed. 95% confidence intervals were estimated as a measure of uncertainty of effect. Differences between the test scores and time taken were analysed using paired student t test. Between-group differences were analysed using an independent student t-test.
 
Results
 
28 patients and 11 controls were recruited. No potential participants were excluded and no participant had a history of dementia. Significantly, the patient group was older, had a greater proportion of male participants and lower average MoCA score than the control group. Patient and control results are summarised in Table 1.
 
Table 1: Summary of patient and control characteristics and main findings.
 
Within groups there were also significant differences. Participants with Parkinson's disease had significantly lower MoCA scores (23.5 ± 4.7) than MMSE scores (27.0 ± 2.6) (mean difference 3.5, 95% CI 2.1- 4.9, t = 5.1962, p=<0.001). This is demonstrated graphically in Figure 1. Likewise, controls had significantly lower MoCA scores (26.7 ± 2.7) than MMSE scores (28.4 ± 1.6) (mean difference 1.6, 95% CI 0.3-3.0, t = 2.6312, p=0.025).
 
Figure 1: Graphical comparison of MMSE and MoCA scores in participants with Parkinson's disease.
 
Test duration was also significantly different within both groups. Participants with Parkinson's disease had significantly longer MoCA test durations (9.4 ± 3.2) compared to MMSE durations (7.6 ± 2.2) (mean difference -1.9, 95% CI -3.2- -0.1, t=3.0977, p=0.007). Similarly controls had significantly longer MoCA duration (8.3 ± 2.4) compared to MMSE duration (6.1 ± 1.7) (mean difference -2.3, 95% CI -3.6- -1.0, t=3.8326, p=0.003).
 
 
Ten out of 11 controls were “normal” on MMSE and MoCA. Only one participant scored 25 on MMSE, but 24 on MoCA, indicating mild cognitive impairment as assessed by the MoCA.
 
In the patient group, the MMSE identified mild cognitive impairment in six patients (21.4%) while the MoCA identified a further ten (35.7%), indicating 57.1% of patients had mild cognitive impairment. The gap between MMSE and MoCA in these five participants not detected by the MMSE was large. For example, three participants scored perfect scores in the MMSE, but 21, 23 and 25 in the MoCA. This observation was supported by a significantly larger mean difference in scores for these five participants than the mean overall difference (6.3 ± 2.8 versus 3.0 ± 3.4, 95% CI 1.0-5.6, t=2.9255, p=0.005).
 
Discussion
 
This study occurred in a monthly specialist Parkinson’s disease outpatient clinic which has limited specialist availability. In this regional setting, it is vital for cognitive impairment to be screened for promptly and reliably, using a tool that requires minimal or no training so that further services can be arranged by non-specialist staff. Even though neuropsychological testing is considered to be the goldstandard for assessing cognitive impairment but this assessment is too time-consuming to be done routinely and requires trained assessors.
 
This study therefore compared the MMSE and MoCA cognitive screening tools in Parkinson's disease and controls to quantify a difference, if any, in test scores in preparation for a more comprehensive validation of the newer MoCA tool.
 
Overall, it was found that the MoCA detected more cases of mild cognitive impairment in patients than the MMSE, supporting the summary findings of Chou et al. [10]. This study also supports the findings of the four small studies which have specifically compared the results of the MMSE to MoCA in patients with Parkinson’s disease, [3,4,9,11] particularly Gill et al who found the difference between the two tests to be statistically and clinically significant [9]. Here, a significant difference was found between patient and control MoCA scores alone.
 
These results highlight two important points. Firstly, that when the MMSE detected cognitive impairment, MoCA scores were similar, which may indicate the MoCA is capable of assessing similar domains of mild cognitive impairment to that of the MMSE. However, when the MoCA detected additional cases of mild cognitive impairment, MMSE scores were near normal. The breadth of cognitive domains assessed using the MoCA may account for the high correlation Gill et al found when compared with a neuropsychological battery (r=0.72) [9].
 
Secondly, this study reinforced the value of screening for mild cognitive impairment in Parkinson's disease early on in the disease process. Of all new patients presenting to the clinic over a sixmonth period, eight were found to have mild cognitive impairment. This prevalence (57.1%) is at the extreme end of recent prevalence studies despite the relatively young average age of participants [1]. As impairment was in executive functioning and visuospatial domains rather than memory, these are cases that may have been missed and resulted in less rigorously monitored prescription of therapies such as dopamine agonists with known cognitive side effects.
 
Cognitive impairment, even if mild, impacts on both the likelihood of further cognitive decline and dementia and on the prognosis of the disease. Cognitive impairment not only impacts patients with Parkinson’s disease and their carers, but also the community when the economic costs of nursing home and hospital care are recognised. An additional benefit to the community has been hypothesised by Mamikonyan and colleagues; that as mild cognitive impairment predicts future cognitive decline, it may eventually be a target for pharmacological intervention [5]. A more sensitive screening tool for detecting cognitive impairment would therefore provide a clearer target for interventions, and provide patients with appropriate early support. Neuropsychological testing is not appropriate for this purpose as it is time-consuming and requires trained assessors.
 
Therefore, this study provides additional support for the use of the MoCA as a screening tool in clinical assessment of patients with Parkinson’s disease and for the first time, demonstrates a clear difference in MoCA and MMSE sensitivity in an Australian population of patients with Parkinson’s disease. Reporting of a significant difference in test scores in a population with Parkinson’s disease is the first step towards a comprehensive validation study in the wider population.
 
Acknowledgements
 
We would like to acknowledge the assistance of Cathie MacKay for her reception and coordination of participants, and Peter Spence, and the Mid-North Coast Division of General Practice (MNCDGP), for their support for this study.
 
Competing Interests
 
All authors declare: no support from any organization for the submitted work; no financial relationships with any organizations that might have an interest in the submitted work in the previous 3 years; any other relationships or activities that could appear to have influenced the submitted work.
 
 
References