Polysomnography results and cognitive performance in early‐stage Parkinson’s disease

Abstract

AbstractBackgroundParkinson’s disease (PD) is a progressive neurological disorder that involves a range of motor and non‐motor symptoms. About 66% of individuals with PD report sleep disturbance impacts their quality of life. Sleep disorders may precede the cardinal motor features in PD and can influence motor and non‐motor symptom severity, including cognition. Yet current evidence of this association with objective assessments remains limited. The goal of this pilot study was to evaluate the associations between cognition and overnight polysomnography results in early‐stage PD.MethodsParticipants completed neuropsychological assessments and an overnight in‐clinic polysomnography. Associations between polysomnography results and cognitive performance were evaluated using partial correlations controlling for age and education.ResultsTwenty participants (mean age 69±8; 25% female) without dementia and with a diagnosis of early‐stage PD (Hoehn and Yahr stage 1‐2) were enrolled (Table 1). Table 2 displays the associations between polysomnography results and cognitive assessments. Greater percentage time in stage N1 sleep and increased duration of wakefulness time after sleep onset (WASO) were associated with poorer phonemic fluency (r = ‐0.626, p = .005 and r = ‐0.512, p = .030, respectively); whereas increased time spent in stage N2 sleep and higher sleep efficiency index were correlated with better phonemic fluency (r = 0.829, p < .001 and r = 0.513, p = .029, respectively). Greater percentage in stage N2 was associated with better verbal learning (Hopkins Verbal Learning Test–Revised (HVLT‐R) Immediate Recall, r = 0.521, p = .027). Higher percent time in REM sleep was correlated with increased basic attention (Digit Span Forward, r = 0.483, p = .042). No associations were found between total sleep time and cognitive performance.ConclusionWhile total sleep time was not associated with cognition, higher percent time spent in Stage N2, Stage N3, and REM sleep were associated with better cognitive performance. In contrast, higher percentage of Stage N1 sleep and increased duration of WASO were associated with poorer verbal fluency. The preliminary results highlight the importance of increased time in deeper stages of sleep for cognition in adults with early‐stage PD. Future longitudinal studies will be necessary to evaluate long‐term cognitive trajectories and transition to dementia in association with diminished sleep quality in Parkinson’s disease.