Parkinsonian signs in subjects with mild cognitive impairment

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Abstract
Background: Parkinsonian signs such as gait disturbance, rigidity, bradykinesia, and tremor are common among individuals with dementia and are associated with negative outcomes, but little is known about parkinsonian signs among individuals with mild cognitive impairment (MCI). Objective: To examine the extent to which MCI is associated with parkinsonian signs and the relation between cognitive abilities and parkinsonism among individuals with MCI. Methods: Participants included 835 individuals from the Rush Memory and Aging Project, a clinical-pathologic study of common chronic conditions of old age. All participants underwent detailed clinical evaluations which included assessments of parkinsonian signs and cognitive function, and linear regression models were used to examine the associations of MCI and parkinsonism. Results: In a series of analyses controlled for age, sex, and education, individuals with MCI exhibited significantly more parkinsonism than individuals without cognitive impairment, particularly gait disturbance, bradykinesia, and rigidity. Among individuals with MCI, lower levels of cognitive function, particularly in perceptual speed, were associated with higher levels of parkinsonism; when classified according to MCI subtype, individuals with amnestic vs non-amnestic MCI differed from each other on only one parkinsonian sign, with non-amnestic MCI showing more gait disturbance. Because vascular factors can contribute to cognitive impairment and parkinsonian signs, the authors repeated the core analyses including terms for vascular risk factors and vascular disease and the associations between MCI and parkinsonism persisted. Conclusions: Mild cognitive impairment (MCI) is accompanied by parkinsonian signs, which are related to the severity and type of cognitive impairment. The association between MCI and parkinsonism is not explained by vascular risk factors or vascular disease.