Seven hours of sleep is the ideal amount of sleep for middle-aged and elderly people, US and Chinese scientists argue in the journal Nature Aging. The conclusion of the study is that significantly more or less sleep is associated with impairment of mental health and poorer mental performance.
Specifically, scientists from the Universities of Cambridge and Fuhan examined data from nearly 500,000 adults between the ages of 38 and 73 collected in the UK Biobank, a comprehensive British database. The subjects were asked about their sleep patterns, mental health and well-being, and also took part in a series of cognitive tests. MRI images of the brain and genetic data were available for almost 40,000 participants.
The analysis of all this information showed that both too little and too much sleep was associated with reduced cognitive performance – the corresponding subjects were slower on the tests and had a shorter attention span and poorer problem-solving skills. Their mental health also suffered: people who got too much or too little sleep showed more symptoms of anxiety and depression and lower overall well-being. According to a guideline from the US National Sleep Foundation (NSF) adults should sleep between seven and nine hours. However, their authors emphasize that the need for sleep differs from person to person.
Analysis of the brain scans also revealed an association between different sleep durations and differences in the structure of brain regions involved in cognitive processing and memory. Among them was the hippocampus, which is considered the memory center of the brain.
Overall, the conclusion in the new specialist article is that seven hours of sleep without major fluctuations seems to be the most ideal for the cognitive performance, general well-being and mental health of middle-aged and older people. Although the study did not describe causality, the results indicated that insufficient or excessive sleep duration could be a risk factor for cognitive decline in old age.
Author Jianfeng Feng emphasizes in a statement: “While we cannot definitively say that too little or too much sleep causes cognitive problems, our analysis, which looks at people over a longer period of time, seems to support this idea.” However, the reasons older people slept poorly seemed complex, involving a combination of genetics and brain structure.
Neuropsychologist and co-author Barbara Sahakian adds that good sleep is important at all stages of life, but especially as we age: “Finding ways to improve the sleep of older people could be crucial in helping them improve their mental health and well-being and to avoid cognitive decline, particularly in patients with psychiatric disorders and dementia.