Sleep, Perivascular Spaces, and Cognition in Alzheimer's Disease and Parkinson's Disease

Cognitive dysfunction, particularly involving memory and executive function, is a core component of neurodegenerative conditions, such as Alzheimer’s disease and Parkinson’s disease. Two factors that are likely related to and may contribute to these cognitive deficits are sleep changes and enlarged perivascular spaces, which are an indicator of cerebral small vessel disease. In addition to being related to cognition, they may also be interconnected, further exacerbating their impact on cognition. This dissertation lays out our current knowledge on these topics and explores the association of these factors with cognition. In this dissertation, I investigated the relationship that perivascular space volumes and sleep (i.e., sleep duration or sleep quality) have with cognitive performance and cognitive status category in Alzheimer’s disease and Parkinson’s disease. Study 1 included individuals with Alzheimer’s-related mild cognitive impairment (MCI) or dementia. Among the individuals with Alzheimer’s disease, longer sleep durations were related to lower memory and executive function performance, and larger white matter perivascular space volumes exacerbated the relationship between longer sleep durations and memory after accounting for relevant covariates. Study 2 included individuals with Parkinson’s disease with intact cognition, MCI, or dementia. Analyses revealed an interaction in which individuals with Parkinson’s disease with smaller white matter perivascular space volumes and better sleep quality exhibited better executive function performance after accounting for relevant covariates. There was also a significant negative correlation between sleep quality and white matter perivascular spaces, and this correlation stayed relatively consistent when covariates were individually included in the model. Finally, analyses across cognitive status groupings revealed that individuals with Parkinson’s disease with MCI exhibited significantly larger white matter perivascular space volumes relative to those with intact cognition, but no other group differences were observed. These results indicate that cognition has a complex relationship with perivascular spaces and/or sleep in Alzheimer’s disease and Parkinson’s disease and that some indicators of sleep and perivascular space volume may be related to cognitive abilities in these populations.