sleep brain health

I’ve reported multiple times on sleep and how it affects just about everything form cognitive performance, to brain plasticity, to physical performance, to mental health, and to metabolism.

The question that remains open is, however, how much sleep is ideal? The old advice of eight hours is pretty close to the truth, but it also changes over lifetimes. We all know that babies need a lot more sleep, for example. Teenagers also seem to sleep a lot.

Research into pre-industrial societies showed, what was surprising at the time, that they don’t sleep as much as many had thought, normally between six and eight hours a night on average.

In comes this recent study out of the University of Cambridge. They analysed data from almost 500,000 people between the ages of 38 and 73. These were asked about their sleep patterns, mental health, and wellbeing, and also took cognitive tests. There was brain imaging and genetic data available for about 40,000 of these participants. That’s a pretty impressive dataset!

We have known for a long time that too little sleep impedes cognitive performance and can lead to multiple negative health impacts. However, what was surprising about this data is that it showed that too little or too much sleep had similar impacts. That is, reduced cognitive performance, more anxiety, increased symptoms of depression, and worse wellbeing overall. They also found links to the size of brain areas associated with cognitive performance

What was the ideal amount of sleep? It was seven hours sleep.

However, the researchers also noted that consistency was key – firstly in getting a solid seven hours rather than an interrupted seven hours, and this being consistent from night to night.

I was also relieved to read the above having independently found that 7 hours 15 minutes is my optimal sleep duration and have managed to stick to this consistently in recent years. However, I am trying to catch up on a few decades of sleep abuse also!


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

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