High prevalence of parkinsonism in patients with MCI or mild Alzheimer's disease.

INTRODUCTION: The objective of this study was to examine the prevalence of the coexistence of parkinsonism in patients with mild cognitive impairment (MCI) or mild Alzheimer's disease (AD).

METHODS: Outpatients were evaluated with Mini-Mental State Examination, Clinical Dementia Rating Scale, NIA-AA criteria, MRI, and 123 I-IMP SPECT (3D-SSP). Parkinsonism in patients diagnosed with MCI (Mini-Mental State Examination ≥24, n = 63) or mild AD (Mini-Mental State Examination 20-23, n = 43) was examined using the Unified Parkinson's Disease Rating Scale-III and 123 I-FP-CIT dopamine transporter SPECT.

RESULTS: One hundred six patients (60-97 years) were enrolled. Fifty-six patients (52.8%) were diagnosed as having concomitant parkinsonism with rigidity and resting tremor and dopamine transporter reduction in the basal ganglia. The mean (SD) age (n = 56) was 80.6 (6.1) years, significantly older than patients without parkinsonism [77.6 (7.0) years, n = 50] (P < .05). The mean (SD) UPDRS-III score was 5.8 (2.4).

CONCLUSION: The prevalence rate of the coexistence of mild parkinsonism in MCI or mild AD may be higher than previously recognized.