Such stuff as dreams are made?

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..


https://www.ncbi.nlm.nih.gov/pubmed/28835407

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

OBJECTIVE:

Sleep disturbance is common in dementia, although it is unclear whether differences in sleep architecture precede dementia onset. We examined the associations between sleep architecture and the prospective risk of incident dementia in the community-based Framingham Heart Study (FHS).

METHODS:

Our sample comprised a subset of 321 FHS Offspring participants who participated in the Sleep Heart Health Study between 1995 and 1998 and who were aged over 60 years at the time of sleep assessment (mean age 67 ± 5 years, 50% male). Stages of sleep were quantified using home-based polysomnography. Participants were followed for a maximum of 19 years for incident dementia (mean follow-up 12 ± 5 years).

RESULTS:

We observed 32 cases of incident dementia; 24 were consistent with Alzheimer disease dementia. After adjustments for age and sex, lower REM sleep percentage and longer REM sleep latency were both associated with a higher risk of incident dementia. Each percentage reduction in REM sleep was associated with approximately a 9% increase in the risk of incident dementia (hazard ratio 0.91; 95% confidence interval 0.86, 0.97). The magnitude of association between REM sleep percentage and dementia was similar following adjustments for multiple covariates including vascular risk factors, depressive symptoms, and medication use, following exclusions for persons with mild cognitive impairment at baseline and following exclusions for early converters to dementia. Stages of non-REM sleep were not associated with dementia risk.

CONCLUSIONS:

Despite contemporary interest in slow-wave sleep and dementia pathology, our findings implicate REM sleep mechanisms as predictors of clinical dementia.