On Wednesday 24 June 2020, T.S. Lysen will defend his PhD dissertation, entitled: ‘Sleep and the Risk of Neurodegenerative Disease. A population-based approach’.
Sleep serves essential functions for the brain to support daytime performance. The brain processes regulated by sleep show overlap with dysfunctional processes involved in neurodegenerative disease. Against this background, poor sleep has been suggested as a potential risk factor for such disease. The aim of this thesis was to investigate sleep and its causal role in neurodegenerative diseases, specifically dementia and Parkinson’s disease, and related brain aspects, in middle-aged and elderly persons. We used data from from the prospective population-based Rotterdam Study cohort.
We described sleep with a systematic review of population-based studies and an individual-level meta-analysis, showing that adults often have sleep complaints although they report sleeping for a recommended or appropriate duration. Poor subjective sleep quality was not related to risk of all-cause dementia or Alzheimer's disease, while poor sleep objectively estimated with accelerometry (actigraphy) was associated with an increased risk of both outcomes. The latter association seemed not explained by presence of neurodegeneration or beta-amyloid accumulation as indicated by plasma biomarkers. Actigraphy-estimated fragmented or unstable 24-hour activity rhythms, as indicators of circadian dysfunction, were not related to incident dementia or Alzheimer's disease.
We further showed that a decrease in sleep quality and duration seem to be prodromal features of Parkinson’s disease, starting on average over 2 years before a diagnosis. Findings i) provide norms for sleep and suggest targeting sleep quality, not sleep duration, to improve sleep at a population level; ii) guide further research on the potential causal role of poor sleep in neurodegenerative disease risk.
The PhD defences will not take place publicly in the Senate Hall or Professor Andries Queridoroom due to the coronavirus. The candidates will defend their thesis online.