Nodding off during the day could be an early warning sign of Alzheimer’s disease, according to research.
A study of nearly 300 retired people found those who reported being very sleepy during the day had higher accumulations of amyloid plaques in their brains – a major cause of Alzheimer’s.
Scientists believe this is because the human brain clears away amyloid when the body is asleep.
So people who are suffering broken sleep at night – and therefore struggling to stay awake during the day – are more likely to have build-ups of the toxic substance.
The US researchers, from the Mayo Clinic in Rochester, Minnesota, said ‘excessive daytime sleepiness’ in elderly people should be considered a red flag for Alzheimer’s.
The scientists, whose work is published in the JAMA Neurology journal, tracked 283 participants aged over 70 between 2009 and 2016, none of whom had dementia at the beginning of the study.
The scientists assessed their levels of daytime sleepiness and conducted at least two brain scans on each participant.
The fifth of the participants which suffered from daytime sleepiness were the most likely to show build-ups of amyloid, a sticky protein which forms plaques in the brain.
They found particular build-ups in the precuneus, the part of the brain linked to episodic memory, and the cingulate gyrus which is linked to emotion, learning, and memory.
The scientists wrote: ‘Excessive daytime sleepiness (EDS) was associated with increased amyloid-beta accumulation in elderly persons without dementia.
‘Early identification of patients with EDS and treatment of underlying sleep disorders could reduce amyloid-beta accumulation in this vulnerable group..’
They said ageing has been linked with daytime drowsiness with research showing up to three-in-ten older adults fall asleep in the day and have ‘frequent sleep attacks’.
It comes after a separate study last year found people who slept poorly were more likely to have amyloid or another protein called tau in their spinal fluid.
The researcher behind that study, Dr Barbara Bendlin of the University of Wisconsin-Madison, said: ‘There are already many effective ways to improve sleep.
‘It may be possible that early intervention for people at risk of Alzheimer’s disease may prevent or delay the onset of the disease.’