In people ages 50 to 60 years old, getting less than six hours of sleep each night is linked to a significantly higher risk of developing dementia later on compared with getting seven or more hours of sleep, according to a new study published in the journal Nature Communications.
The study authors noted that sleep disruption is common in people with dementia, but it’s unclear whether sleep patterns before old age are linked to a later risk of developing dementia. For the latest study, they were interested in exploring this potential link, looking at data from 7,959 study participants who were followed for an average of 24.6 years. During this follow-up period, 521 study participants developed dementia — mostly after age 70, with an average age of 77.1 at diagnosis. The researchers then compared sleep patterns at ages 50, 60, and 70 with the risk of developing dementia.
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There were some notable differences between participants who regularly slept for about seven hours regularly (considered a normal duration for the purposes of the study) and those who slept less than six hours or eight hours or longer regularly. They were more likely to be men — 69.1% in the normal duration group, compared with 67.1% of short sleepers and 61.5% of long sleepers. They were more likely to be white — 91.5% in the normal duration group, compared with 89.6% of short sleepers and 86.3% of long sleepers. They were also more likely to have a history of better cardiovascular, metabolic, and mental health — indicating that getting a normal amount of sleep could be the result of having good health, not just a potential cause of good health.
Sleep duration in middle age linked to dementia risk
During the follow-up period, the lowest risk of dementia was seen in people who reported about seven hours of sleep per night, regardless of the age at which this sleep duration was recorded. After adjusting for social and demographic factors — like age, race, and income and education levels — the researchers found that a shorter sleep duration was still linked to a higher risk of developing dementia. When they further adjusted for health behaviors and cardiovascular, metabolic, and mental health history, there was still a significant link between sleep duration at age 50 and 60 and the risk of developing dementia — with short sleep duration at 50 linked to a 22% higher dementia risk, and short sleep duration at 60 linked to a 37% higher dementia risk. There was no clear link between a long sleep duration (eight hours or longer) and dementia risk.
The researchers also found that among participants with a history of mental illness before age 65, the link between sleep duration and dementia risk was similar to what was seen in the overall group — indicating that sleep is important in preventing dementia regardless of a person’s psychological health. Limitations of the current study, they noted, included relying on electronic health records to record a diagnosis of dementia and the small number of long sleepers, which made it difficult to know whether sleeping for a long duration is linked to dementia.
“There is a widely acknowledged association between sleep and cognitive function, primarily due to the role of sleep in learning and memory, synaptic plasticity” — forming new connections in the brain — “and waste clearance from the brain,” the researchers wrote. “Public health messages to encourage good sleep hygiene may be particularly important for people at a higher risk of dementia.”
Want to learn more about maintaining cognitive health with diabetes? Read “Nine Tips to Keep Your Memory With Diabetes,” “Keeping Your Brain Strong With Diabetes” and “Memory Fitness: How to Get It, How to Keep It.”
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