Mild cognitive impairment is common in Parkinson's disease patients with normal Mini-Mental State Examination (MMSE) scores
Introduction
Cognitive impairment in the absence of frank dementia, typically called mild cognitive impairment (MCI), occurs frequently in Parkinson's disease (PD) [1], [2], even among those newly diagnosed [3], [4]. Impairments in executive function, attention, visuospatial skills and memory have all been reported, whereas language and praxis are thought to be relatively spared [3], [5]. When a discrepancy in cognitive performance has been reported, greater impairment has been found on executive measures than memory measures [6], [7].
Identification of MCI in PD is important, as it predicts future cognitive decline [2], [5], [8] and may eventually be a target for pharmacologic intervention to prevent or delay the development of dementia. Given the common occurrence of a range of cognitive deficits at all stages of PD, routine cognitive screening of all PD patients with a sensitive assessment is important.
The Mini-Mental State Examination (MMSE) [9] remains the “gold standard” screening instrument for global cognition. The MMSE is used extensively in PD, but its use in this population has been questioned [10], [11], both because the MMSE assesses primarily memory and language skills (i.e., not broad enough), and because it may not be sensitive enough to detect many cases of MCI (i.e., instrument ceiling effect).
Given the existing limitations in our knowledge of MMSE performance in PD, we present results on the frequency and correlates of cognitive impairment in PD patients with intact global cognition based on MMSE performance.
Section snippets
Subjects
The study population consisted of a convenience sample of idiopathic PD patients recruited from movement disorders centers at the University of Pennsylvania and the Philadelphia Veterans Affairs Medical Center. Subjects completed an extensive psychiatric, neuropsychological, and neurological battery as part of a study on the frequency and correlates of psychiatric and cognitive complications in PD. The neuropsychological battery was chosen to focus on memory and executive function abilities,
Frequency of impairment by neuropsychological test
Memory domain impairment was found in 15.1% of subjects, with 21.7%, 20.8%, and 14.2% demonstrating impairment on free recall, retention, and recognition discrimination subtests, respectively (Table 2). Executive function domain impairment was found in 8.5% of subjects, with 15.1% impaired on the TOL-DX, 11.3% on the STRP, and 7.5% on verbal fluency. Lastly, 17.0% of patients were impaired in attention, with 17.0% impaired in the backward digit span and 0.9% on the forward digit span.
Frequency of impairment by cognitive domain
A total of
Discussion
We found that mild cognitive impairment, either in single or multiple cognitive domains, occurs in almost one-third of PD patients with intact global cognition as defined by a normal score on the MMSE. In addition, memory deficits, including retrieval deficits, are as common as executive function and attention deficits at the initial stage of cognitive impairment. Finally, anti-anxiety medication use and excessive daytime sleepiness may be reversible or treatable contributors to mild cognitive
Acknowledgment
Funded in part by NIMH grant #067894.
References (43)
- et al.
Development of the University of Pennsylvania smell identification test: a standardized microencapsulated test of olfactory function
Physiol Behav
(1984) - et al.
Impaired extradimensional shift performance in medicated and unmedicated Parkinson's disease: evidence for a specific attentional dysfunction
Neuropsychologia
(1989) - et al.
Neuropsychological profile of patients with Parkinson's disease without dementia
Dement Geriatr Cogn Disord
(2003) - et al.
Evolution of cognitive dysfunction in an incident Parkinson's disease cohort
Brain
(2007) - et al.
Cognitive profile of patients with newly diagnosed Parkinson disease
Neurology
(2005) - et al.
The cognitive ability of an incident cohort of Parkinson's patients in the UK. The CamPaIGN study
Brain
(2004) - et al.
Defining mild cognitive impairment in Parkinson's disease
Mov Disord
(2007) - et al.
A longitudinal study of neuropsychological change in individuals with Parkinson's disease
Int J Geriatr Psychiatry
(2003) - et al.
Visual perception in Parkinson disease dementia and dementia with Lewy bodies
Neurology
(2004) - et al.
Subtypes of mild cognitive impairment in Parkinson's disease: progression to dementia
Mov Disord
(2006)
“Mini-Mental State”: a practical method for grading the cognitive state of patients for the clinician
J Psychiatr Res
A comparison of the mini mental state exam to the montreal cognitive assessment in identifying cognitive deficits in Parkinson's disease
Mov Disord
Cognitive assessment of a representative community population with Parkinson's disease (PD) using the Cambridge Cognitive Assessment-Revised (CAMCOG-R)
Age Ageing
The meaning of cognitive impairment in the elderly
J Am Geriatr Soc
Population-based norms for the Mini-Mental State Examination by age and educational level
JAMA
Medication use patterns among demented, cognitively impaired and cognitively intact community-dwelling elderly people
Age Ageing
The Hopkins verbal learning test—revised
The Stroop color and word test
Norms for letter and category fluency: demographic corrections for age, education, and ethnicity
Assessment
Tower of London-Drexel (TOLDX), technical manual
Comprehensive norms for an expanded Halstead-Reitan battery: demographic corrections, research findings, and clinical applications
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