Dementia and Sleep

Many elderly adults sleep more inefficiently, spending more time in bed with less actual sleep time. If memory problems start to surface in these individuals, a family member might assume they are suffering early signs of dementia, when in fact a better quality and consolidation of sleep could be a quick fix for the memory problems.
For those who do have dementia, of which the commonest type (70% of cases) is Alzheimer’s (AD), there are fundamental correlative concerns as regards total sleep time and character. Sleep often worsens in being more fragmented and less deep prior to the diagnosis of AD. The fundamental cortical build-up of destructive tau and beta-amyloid plaque, the pathologic process in AD, is in the frontal lobe, exactly where deepest sleep is generated in the brain. Thus, it is no wonder that sleep is less deep and fulfilling in AD patients.
A second disturbance is the development of REM sleep behavior disorder (RBD), again often predating the other cognitive and behavioral changes leading to a diagnosis of dementia. See another part of this website for a fuller description of RBD, a troubling sleep disorder. Also, having poorer sleep from AD actually hastens the process of accumulating beta-amyloid, making the AD process advance faster. Finally, poorer quality and shorter duration of sleep increase the risk of developing Alzheimer’s in the first place.
Mander, B. et al, β-amyloid disrupts human NREM slow waves and related hippocampus-dependent memory consolidation” in Nature Neuroscience. Published online June 1, 2015 doi:10.1038/nn.4035
Nedergaard, M., Goldman SA. “Glymphatic failure as a final common pathway to dementia.” Science.. 2020 Oct 2; 370(6512):50-56.
Walker, M. Why we sleep, Simon and Schuster, 2017, pp. 98, 157-9