Global cognitive performance is associated with sleep efficiency measured by polysomnography in patients with Parkinson's disease.

Aim: Sleep disorders can be associated with an increased risk for cognitive decline in patients with Parkinson's disease (PD). The aim of this study was to examine the association between cognitive status and presence of sleep symptoms and sleep disorders in PD patients.

Methods: We evaluated excessive sleepiness, other sleep symptoms, and performed polysomnography and neuropsychological evaluation in 79 patients. They were classified as having normal cognition (PDNC), mild cognitive impairment (PDMCI), or dementia (PDD).

Results: There were 29 PDNC, 39 PDMCI, and 11 PDD patients. PDD patients were older, had higher scores on the Unified Parkinson's Disease Rating Scale, and lower Schwab and England Activities of Daily Living scores than PDNC patients. After analysis of the polysomnographic variables, it was also found that PDD patients had a lower sleep efficiency, lower total sleep time, and lower number of sleep state changes than PDNC patients. In a stepwise analysis, defining Mattis Dementia Rating Scale scores as the dependent variable, the results were a model that selected three variables that accounted for 59% of the variation in the Mattis Dementia Rating Scale score: wake time after sleep onset, number of state changes, and schooling.

Conclusion: We found a significant association between global cognitive performance and wake time after sleep onset and the number of state changes during sleep measured in the polysomnography of PD patients. However, we did not find any other association between sleep disorders or symptoms and cognitive status or cognitive performance of PD patients.