Measuring mild cognitive impairment in patients with Parkinson's disease

Area of Science:

• Neurology
• Neuropsychology
• Cognitive Science

Background:

• Parkinson's disease (PD) is often associated with cognitive impairment, specifically Parkinson disease with mild cognitive impairment (PD-MCI).
• The Movement Disorders Society (MDS) has proposed new Level 2 criteria for diagnosing PD-MCI.
• Accurate and efficient detection of PD-MCI is crucial for patient management and research.

Purpose of the Study:

• To determine the frequency of PD-MCI and its subtypes using the new MDS Level 2 criteria.
• To evaluate the accuracy of three common cognitive screening tests (Montreal Cognitive Assessment, Scales for Outcomes in Parkinson's Disease-Cognition, Mini-Mental State Examination) in detecting PD-MCI.

Main Methods:

• 139 non-demented Parkinson's disease patients underwent three cognitive screening tests.
• Neuropsychological testing was performed 1-3 weeks later to assess cognitive function.
• PD-MCI diagnosis was based on MDS Level 2 criteria, considering both normative comparisons and decline from estimated premorbid levels.

Main Results:

• Using normative comparisons, 46 patients (33%) met PD-MCI criteria, with 93% having multi-domain MCI.
• Screening test accuracy was suboptimal: Montreal Cognitive Assessment (44% specificity), Scales for Outcomes in Parkinson's Disease-Cognition (33% specificity) at 80% sensitivity.
• Mini-Mental State Examination failed to achieve 80% sensitivity. Considering premorbid decline identified 110 patients (79%) with PD-MCI.

Conclusions:

• The proportion of PD-MCI diagnosis varied significantly based on the definition of cognitive impairment (normative vs. premorbid decline).
• None of the three examined screening tests demonstrated good combined sensitivity and specificity for PD-MCI.
• Further research is needed to operationalize premorbid decline and to investigate other Level 1 criteria tests for PD-MCI detection.