Getting sufficient sleep is key to maintaining a sound mind and body. It is one of the ways to minimize the risk of several illnesses and to keep weight gain at bay.
But how much sleep is too little or too much? Or rather what is the ideal amount of shut-eye one should aim for? While most people would say 8 hours, a recent study conducted by a team of researchers from the University of Cambridge in the UK and Fudan University in China found that seven hours of sleep may be the ideal amount of sleep for middle-aged and elderly people.
The study published in the journal Nature Aging says that seven hours of sleep is ideal for improved cognitive performance and mental health. The researchers analysed data from nearly 500,000 adults aged 38-73 years from the UK Biobank.
The individuals were questioned about their sleeping patterns, mental health and wellbeing, and were asked to take a series of cognitive tests, following which it was concluded that an uninterrupted seven hours of sleep was proper for healthy brain and cognitive functions.
The link between sleep irregularities and impaired cognitive performance
With the help of the brain imaging and genetic data that were available for almost 40,000 of the study participants, the researchers 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.
A sound sleep of seven hours was said to improve cognitive performance and mental health, especially in people suffering from symptoms of anxiety and depression.
“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," says Professor Jianfeng Feng from Fudan University in China.
Furthermore, the findings highlighted that insufficient or excessive sleep duration may be a risk factor for cognitive decline in aging. This is backed by previous studies that have reported a link between sleep duration and the risk of developing Alzheimer’s disease and dementia.
How interrupted sleep affects cognitive functions, increases risk of Alzheimers
The study authors pointed out one possible reason for the link between insufficient sleep and cognitive decline, which was the disruption of slow-wave - ‘deep’ - sleep. According to them, an interrupted sleep of this kind could affect memory consolidation as well as lead to the build-up of amyloid, a key protein that could cause ‘tangles’ in the brain characteristic of some forms of dementia.
In addition, it was also found that insufficient sleep may hinder the brain's ability to get rid of toxins.
Therefore, Professor Barbara Sahakian from the Department of Psychiatry at the University of Cambridge, one of the study’s authors says, “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 dementia.”
However, Professor Jianfeng Feng from Fudan University in China adds, “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.”
