Intra-individual variability in cognitive performance predicts functional decline in Parkinson's disease

Area of Science:

• Neuroscience
• Gerontology
• Clinical Neurology

Background:

• Parkinson's disease (PD) is characterized by cognitive deficits contributing to disability.
• Cognitive intra-individual variability (IIV), a measure of cognitive fluctuation, is linked to cognitive decline in aging but its role in PD functional ability is unclear.

Purpose of the Study:

• To investigate the relationship between cognitive intra-individual variability (IIV) and functional ability in individuals with Parkinson's disease (PD).

Main Methods:

• Utilized de-identified data from 1,228 participants with PD and matched controls from the National Alzheimer's Coordinating Center.
• Assessed functional ability using the Functional Ability Questionnaire (FAQ) and cognitive function via the overall test battery mean (OTBM) and IIV.
• Employed logistic regression to predict baseline functional status, controlling for age, education, cognition, depression, and motor function.

Main Results:

• Participants with PD exhibited lower overall cognitive function (OTBM) and higher IIV, depression (GDS), and motor dysfunction compared to controls.
• Cognitive function (OTBM), IIV, depression (GDS), and gait were significant predictors of functional status, achieving 77% classification accuracy (AUC = .84).
• PD participants with functional impairment at follow-up showed significantly lower OTBM and higher IIV, GDS, and motor dysfunction at baseline.

Conclusions:

• Cognitive intra-individual variability (IIV) independently predicts functional status in Parkinson's disease (PD) patients, even after accounting for other clinical factors.
• Elevated IIV at baseline is associated with the presence of functional impairment in individuals with PD.
• IIV represents a potential biomarker for functional decline in Parkinson's disease.