The study of nearly 500,000 adults between the ages of 38 and 73 found that both too much and too little sleep were associated with poorer cognitive performance and mental health, including anxiety and depression. A steady amount of sleep has also been shown to be beneficial. Professor Barbara Sahakian, of the Department of Psychiatry at Cambridge University, said: “Every time you walk away from seven o’clock you get worse. “It’s very clear that the processes that take place in our brain during sleep are very important for maintaining our physical and mental health.” Good night’s sleep, he added, was important at all stages of life, but especially as we age. “I think it’s just as important as exercise.” One possible reason for the link between poor sleep and cognitive impairment may be slow or deep sleep disturbance, which has been shown to be important for memory consolidation. Lack of deep sleep could also prevent the brain from effectively clearing toxins. The study, which used data from the UK’s Biobank, included brain imaging and genetic data for nearly 40,000 of the study participants. He found that the area of ​​the brain most affected by sleep was the area containing the hippocampus, the memory center of the brain, with more or less sleep associated with less brain volume. The analysis found that people who slept seven hours a night performed better on average on cognitive tests for processing speed, visual acuity, memory and problem-solving skills. However, the work could not prove a causal relationship and the relationship between sleep and certain brain disorders is complex. For example, unusual sleep patterns and insomnia are a common symptom in people with dementia. Scientists are less clear about why spending eight or more hours in bed can cause problems. One explanation is that people who have poor quality, disturbed sleep tend to sleep more – or try to sleep – because they feel tired. “We do not really understand why more sleep would be a problem,” Sahakian said. Subscribe to the First Edition, our free daily newsletter – every morning at 7am Professor Jianfeng Feng, of Fudan University in Shanghai, said: . “The reasons why older people have poorer sleep seem to be complex, influenced by a combination of our genetic makeup and the structure of our brain.” The research is published in the journal Nature Aging.