A new study has found there is an ideal amount of sleep for those who are middle to old age, and it's less than the eight-hour standard often recommended.
The study looked at nearly 500,000 adults aged 38 to 73 and found that cognitive performance and mental health were linked to them getting too much and too little sleep at night.
So how much sleep should people be aiming for? The research shows that seven hours is ideal, and getting it consistently makes it increasingly beneficial.
The research was published in the journal Nature Aging, and one of the study's authors, Cambridge University psychiatry professor Barbara Sahakian, shared with the Guardian how important getting seven hours is.
"For every hour that you moved away from seven hours, you got worse," Sahakian said. "It's very clear that the processes that go on in our brain during sleep are very important for maintaining our physical and mental health."
While health experts would say eating right and living a healthy lifestyle is important to living a long life, Sahakian says sleep is just as crucial.
"I think it is as important as getting exercise," Sahakian said.
The study compiled data from the UK Biobank, which includes brain imaging and genetic data for 40,000 participants in the study. The results of the data showed that the hippocampus, the brain's memory center, was the most affected by too little or too much sleep.
Those who slept for the ideal seven hours a night, on average, had better scores on cognitive tests for processing speed, memory, visual attention, and problem-solving skills.
When looking at why those who didn't get seven performed worse, the study said that the disruption of slow-wave, or deep, sleep could be to blame as a lack of deep sleep prevents the brain from clearing toxins effectively.
When it comes to those who got eight or more hours of sleep, scientists could not understand exactly why it could cause problems, but they have some theories.
"We don't really understand why sleeping longer would be a problem," Sahakian said.
An explanation they cited was that those who have a poor quality of sleep tend to sleep longer since they still feel tired, resulting in not hitting seven hours.
The results of the study do not offer a direct causality for getting too much or too little sleep and poorer brainpower, but Fudan University professor Jianfeng Feng shared that it does support the theory.
"While we can't say conclusively that too little or too much sleep causes cognitive problems, our analysis looking at individuals over a longer period of time appears to support this idea," Feng told the Guardian. "The reasons why older people have poorer sleep appear to be complex, influenced by a combination of our genetic makeup and the structure of our brains."
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