Sleep seems to play an interesting role in neurodegenerative disease. Sleep is important in many metabolic functions and there is some evidence to suggest that disruptions in sleep affect brain protein metabolism. As an example, amyloid beta is released at higher levels during wakefulness - so those who sleep less will be exposed to higher levels of the protein. Another aspect of interest is whether sleep disruption acts as a marker for early neurodegenerative disease, giving an early indication of the build up of abnormal proteins that characterise neurodegenerative disease.
So, disrupted sleep may be a cause or effect of neurodegenerative disease (and it's almost certainly a bidirectional relationship). But wouldn't it be nice if, rather than an expensive immunological treatment, we could prescribe sleep for our patients?
To tease out this relationship, investigators in the US have utilised the large community-based Framingham Heart Study. A sub-group of these participants had extensive sleep investigations and were followed up for dementia for up to 19 years afterwards. They were able to look at different stages of sleep and they found that less REM sleep, which tends to occur in the later stages of the night and is associated with dreaming, was associated with development of all types of dementia.
As ever, there are difficulties with implying causality with this kind of observational study - whilst the authors controlled for multiple factors known to be associated with dementia risk there are likely to be other confounders - for example anxiety levels were not controlled for in this analysis. It will also be important to understand the role played by sleep disorders such as obstructive sleep apnoea and REM sleep behaviour disorder, which we are exploring in PREDICT.
Having said that, I for one will be using this as an excuse to get my full 8 hours..
Sleep architecture and the risk of incident dementia in the community.
Neurology. 2017 Sep 19;89(12):1244-1250. doi: 10.1212/WNL.0000000000004373. Epub 2017 Aug 23.
Pase MP, Himali JJ, Grima NA, Beiser AS, Satizabal CL, Aparicio HJ, Thomas RJ, Gottlieb DJ, Auerbach SH, Seshadri S