Middle-aged adults who sleep six hours or less face an increased risk for dementia, compared to those who regularly clock in seven hours of shut-eye, according to a large-scale study spanning 25 years.

The results suggested persistent short sleep among adults aged 50, 60, and 70 were linked to a 30% greater dementia risk, which held up after accounting for factors like mental health, sociodemographics and cardiometabolic state.

“Persistent short sleep duration was associated with an increased risk of dementia compared to those with persistent normal sleep duration,” study authors wrote.


A team of French researchers published findings in the Nature Communications journal on Tuesday, stemming from a Whitehall II study involving nearly 8,000 British participants. Dementia is a broad term for neurodegenerative disease affecting memory, attention and communication, according to the Centers for Disease Control and Prevention, which estimates 5 million adults aged 65 and over were living with dementia in 2014. The agency projects this figure will more than double to nearly 14 million by 2060.

The risks for dementia significantly increase with older age, especially among those 65 and older, the CDC says, though other risk factors include family history and race/ethnicity.

To reach their conclusions, researchers ran repeat measurements on 7,959 participants’ sleep duration over a course of 25 years, collecting self-reported data but also information from wristwatch accelerometers, and 521 participants went on to develop the disease.

Evidence has suggested sleep supports cognitive performance and clears toxic beta-amyloid protein plaques from the brain, thus sleep deprivation can result in “a detrimental effect,” study authors noted. Amyloid plaques can disrupt nerve cells in the brain in Alzheimer’s disease, said to account for the vast majority of dementia cases.

“Amyloid plaque build-up contributes to poor sleep in older adults through its direct impact on sleep-wake regulator brain regions,” authors wrote.

However, difficulty sleeping is sometimes an early sign of dementia. Dr. Séverine Sabia, corresponding study author at the University of Paris stops short of pinning a causal link between sleep duration and dementia risk. 

“These findings suggest that sleep duration might be a risk factor for dementia in later life,” Sabia said, the Guardian reported. “I cannot tell you that sleep duration is a cause of dementia but it may contribute to its development.”

The corresponding author did not immediately respond to Fox News’ request for comment.