Getting a good night’s sleep is so important for your health and happiness, and for a long time, eight hours was seen as the gold standard.
But now we have research between Cambridge University and Fudan University in China explaining why seven is the optimum.
Sleep isn’t only essential for tip-top cognitive function and maintaining good mental health, it also keeps the brain healthy by removing waste products.
But with age, sleeping can become problematic and getting enough of it, elusive. We have difficulty falling asleep and staying that way. It’s poorer quality too.
So is it these sleep disturbances that contribute to cognitive decline and psychiatric disorders as we age?
The researchers studied nearly 500,000 adults aged 38 to 73 years old from the UK Biobank, asking about their sleeping patterns, mental health and wellbeing, and looked at their performance in cognitive tests.
Brain imaging and genetic data for almost 40,000 of the participants were also examined. Analysis revealed both insufficient and excessive sleep were linked to poorer speed of processing information, visual attention, memory and problem-solving skills.
It turned out the optimal amount of sleep for good cognitive performance and mental health, was seven hours. People sleeping longer or shorter had more symptoms of anxiety and depression, and a worse overall sense of wellbeing.
The researchers say one possible reason for this could be disruption of slow-wave “deep” sleep, which has a close link to poor memory, as well as the build-up of amyloid, whose tangles in the brain are characteristic of some forms of dementia. Lack of sleep may also damage the brain’s structure and hamper its ability to rid itself of toxins.
Previous studies have also shown interrupted sleep in older people is associated with increased inflammation, indicating a susceptibility to age-related diseases.
The findings suggest insufficient or excessive sleep duration may be a risk factor for cognitive decline in ageing.
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.”
There are several safe remedies for an older person to ensure a sound seven-hour sleep at night, so they can rest easy in later life.