Scientists identify the ideal amount of sleep to reach middle age

We spend an average of 3,000 hours in dreamland each year – or in other words, a third of our lives between duvet covers and pillows – and for good reason. Sleep is linked to a number of cognitive and physiological processes in the body, and not getting enough (or sometimes even too much) can have unintended health consequences.

As we age, we can also experience changes in our sleep patterns, and knowing how much sleep is optimal for healthy functioning becomes important. Reporting in the Journal Nature Aging, scientists from Cambridge and Fudan University may have found an answer.

Examining data from the UK BioBank, the researchers analyzed 498,277 participants aged 38 to 73 who completed surveys on their sleep pattern and duration, mental health and general well-being. Of this group, 40,000 participants had brain imaging profiles and additional genetic data available for analysis.

Study results suggest that participants who got approximately 7 hours of sleep a day without major disruptions to their daily sleep patterns for prolonged periods had better cognitive performance and better mental health and general well-being in the long term.

Having less or more sleep appeared to be associated with impaired cognitive performance on tasks such as memory and problem-solving skills and mental health in participants.

The authors also found a link between the amount of sleep and changes in the volume of key brain regions involved in memory, such as the hippocampus and other areas involved in cognitive processing in some participants. They speculate that changes in brain volume and other genetic mechanisms may underpin underlying changes in cognition and mental health during those who had differential sleep duration.

“While we cannot conclusively say that too little or too much sleep causes cognitive problems, our analysis looking at individuals over a long period of time seems 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.” Professor Jianfeng Feng of Fudan University said in a statement.

The authors suggest a possible explanation for why insufficient sleep as we age can lead to cognitive decline, explaining that it may be due to a disruption of slow-wave sleep, which has been linked to dementia and memory difficulties. While the current study doesn’t speculate why sleeping too much can be a bad thing, previous studies have shown that sleeping too much can also lead to cognitive decline.

A certain strength of the current study is the large sample size that was used and therefore the results can be considered robust. However, the authors highlight some limitations. The surveys were self-reported, which may present some bias, and only questioned the participants’ total sleep duration and did not address other aspects, such as sleep hygiene practices.

Future studies could certainly elaborate on these findings, but for now, we can check that as we age, 7 hours of nap every night seems to be ideal when it comes to our napping practices.

“Getting a good night’s sleep is important at all stages of life, but especially as we age. Finding ways to improve sleep for older adults could be crucial to helping them maintain good mental health and well-being and prevent cognitive decline, particularly for patients with psychiatric disorders and dementia.” Professor Barbara Sahakian of the Department of Psychiatry at the University of Cambridge concludes.

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