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Losing out on sleep in middle age can lead to memory problems later in life, according to a new, wide-ranging study.
People who frequently slept for six hours or less a night in their 50s and 60s may be at a 30% higher risk of developing dementia, researchers found, compared to people who were asleep for seven hours a night.
For the study, published in the journal Nature Communications, researchers followed nearly 8,000 people in Britain starting when they were 50 years old and tracked their sleep duration for the next 25 years. Those with six hours or less a night were more likely to develop dementia, even after the researchers accounted for "sociodemographic, behavioural, cardiometabolic, and mental health factors" like depression that could also increase their risk of dementia.
They also considered the study subjects' history of smoking, drinking, their weight, physical activity, food consumption and any health conditions like diabetes, hypertension or heart disease. Still, they found that a lack of sleep in middle age was associated with a heightened risk of dementia.
The study is one of the largest to point to a correlation between sleep and dementia risk, though it does not prove that poor sleep habits causes cognitive decline.
"Even though we can't say sleep duration has a causal impact on dementia, it would be good to encourage good sleep hygiene," Séverine Sabia, an epidemiologist at the French National Institute of Health and Medical Research, also known as Inserm, and the lead author of the study, said, according to the Wall Street Journal.
Sabia said that people could improve their sleep habits if they stop using electronic devices 30 minutes before they go to sleep and incorporate regular exercise into their days.
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Their research could be an important warning about hazards of lost sleep.
"The study found a modest, but I would say somewhat important association of short sleep and dementia risk," Pamela Lutsey, an associate professor of epidemiology and community health at the University of Minnesota, who was not involved in the research, told The New York Times. "Short sleep is very common and because of that, even if it's modestly associated with dementia risk, it can be important at a societal level. Short sleep is something that we have control over, something that you can change."
And the researcher "strengthens the evidence that poor sleep in middle age could cause or worsen dementia in later life," Elizabeth Coulthard, an associate professor in dementia neurology at the University of Bristol in the U.K. who also was not involved in the study, told CNN.