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Without enough sleep it can be hard to concentrate, and irritability can quickly sink in. But did you ever wonder how much sleep is ideal, especially as you age? Researchers at the University of Cambridge’s department of psychiatry and the Institute of Science and Technology for Brain-Inspired Intelligence at Fudan University in Shanghai did, and they discovered seven hours is the optimal amount of shut-eye if you are 40-plus.
Finding the sweet spot in terms of how long you should sleep is particularly important for older adults. Studies have demonstrated a link between sleep duration and the risk of developing Alzheimer’s and dementia.
“Getting a good night’s sleep is important at all stages of life, but particularly as we age,” says Barbara Sahakian, a Cambridge psychiatry professor and one of the study’s authors. “Finding ways to improve sleep for older people could be crucial to helping them maintain good mental health and well-being and avoiding cognitive decline, particularly for patients with psychiatric disorders and dementias.”
More or less than seven hours can harm cognitive performance
To determine how much sleep is ideal to achieve optimal brain function and mental health, researchers from the UK and China tapped the UK Biobank, poring over data from close to 500,000 adults ages 38 to 73. Participants in the UK Biobank were asked questions about their sleeping patterns, mental health and well-being. The study participants also underwent cognitive tests. Brain images and genetic data were available for about 40,000 of the adults.
After analyzing the data, the scientists found too little or too much sleep hurt cognitive performance including processing speed, visual attention, memory and problem solving. Seven hours of sleep, however, improved cognitive performance and mental health. People suffering from anxiety and depression reported worse well-being if they slept too little or too long. The results of the study were published in the journal Nature Aging.
It’s the why of it that researchers are now trying to unearth. One possible reason for cognitive decline with too little or too much sleep could be disruptions to deep sleep, a type of sleep that is closely linked to memory consolidation and the clearing of amyloid, a protein that when misfolded causes knots in the brain that are characteristic of some forms of dementia. The wrong sleep duration may also prevent the brain from unloading toxins, which could hurt cognitive performance. The researchers also said the findings indicate that insufficient or excessive sleep could be a risk factor for cognitive decline as we age. A panel of experts with AARP's Global Council on Brain Health said in a 2016 report that sleep is vital to brain health. The panel recommended seven to eight hours of sleep each day.
