Cholinergic Neurotransmission in Mobility and Cognition in Parkinson Disease

This is a single-site non-randomized open label clinical trial in patients with Parkinson disease (PD) and mild to moderate cognitive deficits, designed to 1) identify associations between cognitive impairment and gait impairment, and 2) identify cognitive domains and gait measures that improve after 12 weeks of treatment with rivastigmine. Aim 1 will be addressed with a cross-sectional approach (arm 1, baseline only, all participants), and aim 2 will be addressed with a longitudinal interventional approach (arm 2, 12 week-treatment with rivastigmine, subgroup of participants). Patients with idiopathic Parkinson disease (PD) and mild to moderate cognitive deficits amounting to PD dementia (PDD) will be enrolled. At baseline (arm 1), all participants will perform the timed-up-and-go test (TUG), wearing a light-weight sensor device strapped to the lower back with a neoprene belt. Participants will also complete a computerized cognitive test battery (NeuroTrax Mild Cognitive Impairment \& Early Dementia Battery by MindStreams). A subgroup of participants (arm 2) will then be treated with transdermal rivastigmine for 12 weeks, with dose increases every 4 weeks and titration up to 13.3 mg/24h, if tolerated. The same assessment (quantitative gait testing and NeuroTrax computerized cognitive test battery) will be repeated after 12 weeks, with the participant on a stable dose of transdermal rivastigmine. The investigators will analyze correlation of iTUG measures and cognitive measures at baseline (cross-sectional analysis). The investigators will also analyze change in iTUG measures and cognitive measures between baseline and follow-up for the subgroup of participants in arm 2 (in other words, before and after rivastigmine treatment; longitudinal analysis).