Sleep is important for many reasons – but experts have warned that too much can actually be bad for your brain.
Official NHS guidance states that most adults need between six and nine hours sleep every night.
Recent studies have however shown that this might not be the case, with some adults needing as little as four hours sleep to wake up feeling refreshed.
Research from experts in Washington, US, found that having too much sleep could actually interfere with your cognitive function.
The experts found that people who slept less than 4.5 hours a night, and those who slept more than 6.5 hours each night had a greater risk of cognitive decline over time.
It’s key to note that all of these participants also struggled with poor quality sleep.
They also found that the impact of sleep duration on the brain had the same effect as aging – which is one of the biggest risk factors when it comes to developing conditions such as Alzheimer’s.
The researchers suggest that for adults, sleeping between 4.5 and 6.5 hours a night is ideal.
Writing in The Conversation, senior lecturer in psychology Greg Elder said researchers don’t know for certain why lack of sleep is linked to cognitive decline.
He said: “One theory is that sleep helps our brain flush out harmful proteins that build up during the day.
“So interfering with sleep might interfere with our brain’s ability to get rid of these.
“Experimental evidence even supports this – showing that even just one night of sleep deprivation temporarily increases beta-amyloid levels in the brain of healthy people.”
He added that the findings of the Washington study are surprising, as most health bodies, including the NHS in the UK and the Centre for Disease Control (CDC) in the US, all state that people should be having more than six hours each night.
“The study showed that sleeping longer than 6.5 hours was associated with cognitive decline over time – this is low when we consider that older adults are recommended to get between seven and eight hours of sleep every night.
“It could be the case that it isn’t necessarily the length of the sleep that matters, but the quality of that sleep when it comes to risk of developing dementia”, he said.
He did however state that it’s key to remember that the 100 participants in the study who slept for longer may have been suffering with issues that were not picked up on the tests.
The researchers had adjusted for dementia-related factors but Greg explained that longer sleepers may also have had other pre-existing conditions that might have contributed to their cognitive decline which weren’t taken into account.
“For example, this could include poor health, socioeconomic status or physical activity levels.
“All of these factors together may explain why longer sleep was linked to cognitive decline,” he added.
It’s in your genes
A separate study, published in San Francisco, US, found that the amount we sleep is actually down to genetics.
Lead author of the study, neurologist Louis Ptacek said: “There’s a dogma in the field that everyone needs eight hours of sleep, but our work to date confirms that the amount of sleep people need differs based on genetics.
“Think of it as analogous to height; there’s no perfect amount of height, each person is different. We’ve shown that the case is similar for sleep.”
The team have been studying sleep patterns for over ten years.
They studied people with Familial Natural Short Sleep (FNSS), the ability to function fully on—and have a preference for four to six hours of sleep a night.
They did however state that studying the genes linked to sleep would be like a ‘thousand piece jigsaw puzzle.’
The experts explained: “Sleep problems are common in all diseases of the brain.
“This makes sense because sleep is a complex activity. Many parts of your brain have to work together for you to fall asleep and to wake up.
“When these parts of the brain are damaged, it makes it harder to sleep or get quality sleep.”
This story originally appeared on The Sun and has been reproduced here with permission.
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