MIDDLE-AGED Brits who sleep less than six hours a night are up to 37 per cent more likely to develop dementia, research suggest.
Experts warn the findings link a lack of night-time rest with poor brain health.
University College London researchers followed nearly 8,000 adults for 36 years.
But for 60-year-olds getting less than six hours of nightly shuteye, their risk of later developing the brain-wasting disease was raised by 37 per cent compared to those snoozing for seven hours.
Researcher Dr Archana Singh-Manoux said: “We know that sleep is important to our brain health, as it is involved in learning and memory, waste clearance from the brain, and the ability of our brain cells to remain healthy.
“A better understand of how sleep features might shape our risk of dementia is needed, as this might help researchers develop new ways to reduce the risk of dementia, or to delay its progression.”
A common symptom of dementia is altered sleep, with experts unsure whether it is triggered by the illness or fuelling it.
Around 850,000 Brits currently have the brain-wasting condition - and the figure is expected to hit one million within a decade.
There is currently no cure, although some drugs can limit the symptoms.
Dr Sara Imarisio, head of research at Alzheimer's Research UK, said: "We know that the diseases that cause dementia start up to two decades before symptoms like memory loss start to show, so midlife is a crucial time for research into risk factors.
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"In this study, sleep duration was largely measured through study volunteers self-reporting their sleep duration, and while this group of volunteers was not reflective of the UK population, it does offer insight into the relationship with sleep and dementia in mid to later life.
"This study cannot tease apart cause and effect and while it suggests that persistent lower sleep duration was linked with an increased risk of dementia, it did not find an association between longer than average sleep duration and dementia risk.
"While there is no sure-fire way to prevent dementia, there are things within our control that can reduce our risk.
"The best evidence suggests that not smoking, only drinking in moderation, staying mentally and physically active, eating a balanced diet, and keeping cholesterol and blood pressure levels in check can all help to keep our brains healthy as we age."