International neurologists have warned taking frequent daytime naps and sleeping too long at night could be early warning signs of dementia, or even contribute to the condition of the brain.
Many older people take ‘forty winks’ and is usually only because they need a physical rest from exertion.
But French researchers who looked at results from 5,000 over 65s found the majority who took regular, long naps scored lower in mental ability tests.
Dr Claudine Berr, from the Institut National de la Santé et de la Recherche Médical (Inserm), told the Alzheimer’s Association International Conference in Vancouver: “These results suggest excessive daytime sleepiness may be an early predictor of cognitive decline.”
In another study, also presented in Vancouver, American researchers found routinely sleeping more than nine hours a night, or less than five, was linked to lower mental ability.
Elizabeth Devore from the Brigham and Women’s Hospital in Boston, Massachusetts, looked at 15,000 former nurses aged over 70 years.
She and colleagues also found those who slept too much or too little exhibited chemical brain changes indicative of early Alzheimer’s, which is the most common form of dementia.
She added over time “extreme sleep durations may contribute to cognitive decline and early Alzheimer’s”, and not simply be a passive sign of them.
Dr Marie Janson of Alzheimer’s Research UK, said: “There is already some evidence linking sleep duration and disturbances to cardiovascular health and diabetes, so it’s not surprising to see studies examining how sleep might affect cognitive ability over time.
“We can already help people to achieve the recommended seven hours, so regulating sleep could become a strategy to protect against cognitive decline if further evidence bears this out.”
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