People should get no more than seven-and-a-half hours of sleep a night in order to delay the onset and worsening of Alzheimer’s disease, new research suggests.
Getting too much sleep – including the often recommended eight hours – was found to increase the likelihood of worsening brain function, a classic symptom of the disease.
“Our study suggests there is a middle range, or ‘sweet spot’, for total sleep time where cognitive performance was stable over time,” said Dr Brendan Lucey, of the Sleep Medicine Centre at Washington Uni-
In the paper, published in the journal Brain, the researchers wrote: “These results support the suggestion that sleep measures have an optimal middle range and suggest targets for sleep interventions to help maintain cognitive function in individuals at risk of developing Alzheimer’s disease.”
Sleep, cognitive decline and Alzheimer’s have long been known to be linked, but determining the relationship has been difficult.
Previous evidence has found that cognitive decline, which manifests itself as memory loss, confusion and taking longer to learn new things, is linked to poor sleep. It is also known to be a symptom of Alzheimer’s, and the disease is thought to be the main cause of cognitive decline in adults.
Dr Lucey recruited 100 elderly people and monitored their sleep for one week a year over several years, using EEG caps that record brain waves and activity.
Tests and questionnaires were used to gauge cognitive performance and alertness, while researchers also took blood samples and vials of cerebrospinal fluid to see whether the participants had high levels of Alzheimer’s-linked proteins in their system.
Most people in the study – 88 – had no cognitive impairments, 11 were very mildly impaired and one had mild cognitive impairment, the researchers said.
Cognitive performance was worse in people who had too much or too little sleep.
Those in the middle range of between five-and-a-half and seven-and-a-half hours showed no signs of worsening cognitive function.
Dr David Holtzman, co-senior author of the report, said it “was particularly interesting to see that not only those with short amounts of sleep but also those with long amounts of sleep had more cognitive decline”, and added: “It suggests that sleep quality may be key, as opposed to simply total sleep.” (©Telegraph Media Group Ltd 2021)
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