How Much Sleep Do We Really Need?

A good night’s sleep plays an important role in our health and cognitive function, it not only helps maintain good overall health, but it also helps in maintaining our psychological health. 

As we get older, we can start having alterations in our sleep patterns, which are thought to contribute to cognitive decline and psychiatric disorders in the aging population. Sleep keeps the brain healthy by removing waste products, which are normally present in high concentrations in neurodegenerative conditions such as Alzheimer’s. 

The duration of sleep is closely related to psychiatric disorders and even dementia in older adults. 

Seven Hours: The “Sweet Spot” Time of Sleep 

A recent study published in the journal Nature Aging, by researchers from the UK and China, evaluated data from about 500,000 adults aged 38 to 73 years from the UK Biobank, in which participants were asked about their sleeping patterns, mental health, and wellbeing. Brain imaging was also available for almost 40,000 participants. 

The research team found that both insufficient and excessive sleep duration was associated with impaired cognitive performance, including processing speed, visual attention, memory, and problem-solving skills. 

The team also observed a link between the amount of sleep and differences in the brain structure, in regions involved in cognitive processing and memory. The most significant brain structures were found to include the precentral cortex, the lateral orbitofrontal cortex, and the hippocampus, which is an area affected in Alzheimer’s disease. This was a critical association found. 

They found that 7 hours of sleep per night was the optimal amount of sleep for cognitive performance and also for good mental health. Also, they observed that people sleeping for both longer or shorter durations reported more symptoms of anxiety and depression. 


Yuzhu Li, Barbara J. Sahakian, et al. 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. 

University of Cambridge. “Seven hours of sleep is optimal in middle and old age, say researchers.” ScienceDaily. ScienceDaily, 28 April 2022.


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