Emerging Science: Does sleeping more protect against dementia?

There is emerging evidence showing that lack of sleep is associated with the accumulation of beta-amyloid in the brain.  Since beta-amyloid is the protein that has been linked to the pathology in Alzheimer’s disease, it is hypothesized that a chronic lack of sleep increases predisposition to Alzheimer’s dementia.  There is evidence from clinical studies, of beta-amyloid accumulation in the brain in chronic sleep deprivation that supports this hypothesis.

If lack of sleep increases predisposition to Alzheimer’s, does the converse hold true – i.e. does increased sleep reduce predisposition to Alzheimer’s.  To study this possibility clinically we need a situation where test subjects chronically increase sleep duration.  Narcolepsy is a disease where the sufferers have problems maintaining an awake state due to a deficiency in the arousal system in the brain.  Although their sleep is not normal and is certainly disturbed at night, narcolepsy patients do sleep for more hours on average across a 24 hour period.

Two recent studies in narcoleptics give substance to the intriguing possibility that narcoleptics have a reduced susceptibility to dementia.  Both studies (listed below) show reduced accumulation of beta-amyloid in the brains of narcolepsy patients.  Separately, sleep extension has been shown to promote cognition even in healthy subjects.

All this leads to a testable hypothesis – “Promoting sleep extension in those at risk of Alzheimer’s disease can delay or prevent the onset of the disease”.  If this is found to be true, then it will be one more among the many many reasons to get a good nights sleep.  How can you find out if you are sleeping enough? You are getting good sleep if you (1) feel refreshed and rested when you wake up, and (2) do not feel sleepy during the day.  You can also take an online version of the Epworth Sleepiness Score (e.g. https://qxmd.com/calculate/calculator_85/epworth-sleepiness-scale) to measure your daytime sleepiness and use this determine if your sleep is sufficient, both in duration and quality.

Promoting good quality sleep may become the latest prevention tool in our armamentarium against Alzheimer’s.  Since there is no downside to getting a good night’s sleep it may be the best and easiest thing you could do to help your health!

 

1. Cerebrospinal Fluid Biomarkers of Neurodegeneration Are Decreased or Normal in Narcolepsy
Poul Jørgen Jennum, MD, Dr Med Sci Lars Østergaard Pedersen, PhDJustyna Maria Czarna Bahl, PhD Signe Modvig, MD, PhD Karina Fog, PhDAnja Holm, PhD Birgitte Rahbek Kornum, PhD Steen Gammeltoft, MD, Dr Med Sci
Sleep, Volume 40, Issue 1, 1 January 2017, zsw006,https://doi.org/10.1093/sleep/zsw006
2. Ann Neurol. 2018 Nov 2. doi: 10.1002/ana.25373. [Epub ahead of print]
Reduced brain amyloid burden in elderly patients with narcolepsy type 1.
Gabelle A1,2,3, Jaussent I2,3, Bouallègue FB2,4,5, Lehmann S2,6, Lopez R2,3,7, Barateau L2,3,7, Grasselli C1, Pesenti C7, de Verbizier D4, Béziat S2,3, Mariano-Goulart D2,4,5, Carlander B7, Dauvilliers Y2,3,7; ADNI and the MAPT-study group.

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