Closeup alarm clock having a good day with background happy woman stretching in bed after waking up, sunlight in morning.

(© oatawa -

CAMBRIDGE, United Kingdom — Seven is the magic number when it comes to sleep for middle age and older adults, according to a new study. Researchers from the University of Cambridge say seven hours is just what the mind needs to maintain strong cognitive performance and mental health.

Previous studies have found that too little or too much sleep as people age can lead to poorer cognition as well as mental health problems. In a new study, examining data from nearly half a million people in the U.K. and China between 38 and 73 years-old, researchers asked participants about their sleeping patterns, mental health, and well-being. They also took part in a series of cognitive tests.

The team found both insufficient and excessive sleep duration had a connection to impaired cognitive performance, including poorer processing speed, visual attention, memory, and problem-solving skills. Seven hours of sleep each night was the optimal amount of sleep for cognitive performance, according to the results.

It was also good for mental health, with people experiencing more symptoms of anxiety and depression and worse overall well-being after sleeping for longer or shorter periods.

Sleep’s ties to preventing dementia

Researchers say one reason for this is that when something disrupts “deep sleep,” it can cause a buildup of a protein called amyloid that “tangles” in the brain. These tangles are one of the hallmarks of dementia onset.

Additionally, lack of sleep may hamper the brain’s ability to rid itself of toxins. Previous studies have also shown that interrupted sleep patterns contribute to 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. 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,” says Professor Barbara Sahakian in a university release.

“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,” adds Professor Jianfeng Feng from Fudan University in China.

The research is published in the journal Nature Aging.

South West News Service writer Joe Morgan contributed to this report.

Our Editorial Process

StudyFinds publishes digestible, agenda-free, transparent research summaries that are intended to inform the reader as well as stir civil, educated debate. We do not agree nor disagree with any of the studies we post, rather, we encourage our readers to debate the veracity of the findings themselves. All articles published on StudyFinds are vetted by our editors prior to publication and include links back to the source or corresponding journal article, if possible.

Our Editorial Team

Steve Fink


Chris Melore


Sophia Naughton

Associate Editor