The Effect of Deep Brain Stimulation on Sleep and Cognition in Patients With Parkinson's Disease.

Sleep-wake disturbances and cognitive decline are among the most common nonmotor symptoms of Parkinson's disease (PD). Deep brain stimulation (DBS) can successfully alleviate motor symptoms. However, the impact on sleep-wake disturbances and cognitive decline, and their interaction, is yet unclear. We aim to investigate changes in and interaction between subjective sleep and cognition following DBS. We performed a study on data from the Amsterdam-PD-DBS database with assessments at baseline and at 6 months post-operative. Subjective sleep was assessed with the sleep and sleepiness items of the Movement Disorder Society-Unified Parkinson's Disease Rating Scale. Cognition was assessed with neuropsychological tests for the domains of language, processing speed, executive functioning, and memory. Three hundred and sixty-five PD patients were included. Subjective sleep and sleepiness significantly improved after DBS. The proportion of patients with clinically relevant sleep disturbances dropped significantly from 76.4% to 50.1% (p < 0.001). Significant declines were observed in verbal fluency (p < 0.001, p = 0.005), processing speed (p < 0.001), and executive function (p < 0.001, p = 0.013), while delayed memory showed a significant improvement (p = 0.025). Significant associations were found for reduction in sleepiness and less decline in category fluency (p = 0.014) while no significant relationship between changes in sleep and changes in cognitive outcomes was present. This study provides strong evidence for the beneficial effects of DBS on sleep and sleepiness. No evidence was found for an association between reduction in subjective sleep disturbances following DBS and change in cognition.