Perfect amount of sleep really is 7 hours, study concludes

How much sleep is the perfect amount? Seven hours of sleep is the “Goldilocks” amount for people in their middle age and upwards, according to new research out of the University of Cambridge in England.

In the study examining data from nearly half a million British and Chinese people aged 38 to 73, participants were asked abut their sleeping patterns, mental health and wellbeing. They also took part in a series of cognitive tests.

Researchers report that both insufficient and excessive sleep duration were associated with impaired cognitive performance, such as processing speed, visual attention, memory and problem-solving skills. Seven hours of sleep per night was the optimal amount of sleep for cognitive performance.

It was also good for mental health, with people experiencing more symptoms of anxiety and depression, and worse overall wellbeing, if they reported sleeping for longer or shorter durations. Researchers say one reason is that when “deep” sleep is disrupted, it can cause a build of a protein called amyloid that can cause “tangles” in the brain similar to some forms of dementia.

Additionally, lack of sleep may hamper the brain’s ability to rid itself of toxins.

Previous studies have also shown that interrupted sleep patterns are associated with increased inflammation, indicating a susceptibility to age-related diseases in older people.

“Getting a good night’s sleep is important at all stages of life, but particularly as we age,” says study co-author Barbara Sahakian, from the Department of Psychiatry at Cambridge, in a statement. “Finding ways to improve sleep for older people could be crucial to helping them maintain good mental health and wellbeing and avoiding cognitive decline, particularly for patients with psychiatric disorders and dementias.”

Adds Professor Jianfeng Feng from Fudan University in China: “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. But 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.”

The research is published in the journal Nature Aging.

Report by Tom Campbell, South West News Service

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Steve Fink

Steve Fink is the Editor-in-Chief of, and He is formerly the Vice President of News Engagement for CBS Television Stations’ websites, and spent 20 years with CBS.


    1. The amount of sleep needed is highly subjective.
      Today 6-7 is perfect for me but when I was younger and working long hours at two very physical jobs I needed 8-9 hours

  1. All biological properties exist on a spectrum. Sleep will be no different.

    7 hours may be the ideal average – odd how it turns out to be an integral hour – but 7 hours will be the ideal average for individuals.

    As for myself, in general I function better on 7, but prefer 8.

  2. I usually fall asleep right around 10:30am with my alarm set to 6:00am but if I don’t then I’m awake until 11:30. When that happens I just hope that I fall asleep before midnight because it’s then likely I stay awake til 2:00am. Ugh

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