Seven hours of sleep is optimal in middle and old age, say researchers


Date:
April 28, 2022
Source:
University of Cambridge
Summary:
Seven hours is the ideal amount of sleep for people in their
middle age and upwards, with too little or too much little sleep
associated with poorer cognitive performance and mental health,
say researchers.



FULL STORY ========================================================================== Seven hours is the ideal amount of sleep for people in their middle age
and upwards, with too little or too much little sleep associated with
poorer cognitive performance and mental health, say researchers from
the University of Cambridge and Fudan University.


========================================================================== Sleep plays an important role in enabling cognitive function and
maintaining good psychological health. It also helps keep the brain
healthy by removing waste products. As we get older, we often see
alterations in our sleep patterns, including difficulty falling asleep
and staying asleep, and decreased quantity and quality of sleep. It
is thought that these sleep disturbances may contribute to cognitive
decline and psychiatric disorders in the aging population.

In research published today in Nature Aging, scientists from the UK and
China examined data from nearly 500,000 adults aged 38-73 years from
the UK Biobank.

Participants were asked about their sleeping patterns, mental health and wellbeing, and took part in a series of cognitive tests. Brain imaging and genetic data were available for almost 40,000 of the study participants.

By analysing these data, the team found 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, but also for good mental
health, with people experiencing more symptoms of anxiety and depression
and worse overall wellbeing if they reported sleeping for longer or
shorter durations.

The researchers say one possible reason for the association between insufficient sleep and cognitive decline may be due to the disruption
of slow- wave -- 'deep' -- sleep. Disruption to this type of sleep
has been shown to have a close link with memory consolidation as well
as the build-up of amyloid -- a key protein which, when it misfolds,
can cause 'tangles' in the brain characteristic of some forms of
dementia. Additionally, lack of sleep may hamper the brain's ability to
rid itself of toxins.

The team also found a link between the amount of sleep and differences
in the structure of brain regions involved in cognitive processing and
memory, again with greater changes associated with greater than or less
than seven hours of sleep.

Having a consistent seven hours' sleep each night, without too much
fluctuation in duration, was also important to cognitive performance and
good mental health and wellbeing. Previous studies have also shown that interrupted sleep patterns are associated with increased inflammation, indicating a susceptibility to age- related diseases in older people.

Professor Jianfeng Feng from Fudan University in China said: "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 researchers
say the findings suggest that insufficient or excessive sleep duration
may be a risk factor for cognitive decline in ageing. This is supported
by previous studies that have reported a link between sleep duration
and the risk of developing Alzheimer's disease and dementia, in which
cognitive decline is a hallmark symptom.

Professor Barbara Sahakian from the Department of Psychiatry at the
University of Cambridge, one of the study's authors, said: "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." The research was supported by the National
Key R&D Program of China, the Shanghai Municipal Science and Technology
Major Project, the Shanghai Center for Brain Science and Brain-Inspired Technology, the 111 Project, the National Natural Sciences Foundation
of China and the Shanghai Rising Star Program.


========================================================================== Story Source: Materials provided by University_of_Cambridge. The original
text of this story is licensed under a Creative_Commons_License. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Yuzhu Li, Barbara J. Sahakian, Jujiao Kang, Christelle Langley, Wei
Zhang, Chao Xie, Shitong Xiang, Jintai Yu, Wei Cheng, Jianfeng
Feng. The brain structure and genetic mechanisms underlying the
nonlinear association between sleep duration, cognition and mental
health. Nature Aging, 2022; DOI: 10.1038/s43587-022-00210-2 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/04/220428125425.htm

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