We know that sleep is an essential part of a healthy brain. However, scientists are continuing to research what a good night's sleep looks like at different stages of life and how it can affect our vulnerability to cognitive decline. A comprehensive new study, in which almost half a million people took part, has yielded compelling new findings: According to this, seven hours of sleep per night is best for brain health in middle and advanced ages.

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Good sleep habits are known to be beneficial from reducing the risk of cancer and heart failure to maintaining a healthy body weight. Recently, however, scientists have also shown the connection with Alzheimer's and dementia.

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Sleeping too much or too little can be a risk factor for age-related cognitive decline.

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These include studies that find an increased risk of interruptions in key sleep phases, short sleep duration, and excessive “daytime naps.” On the positive side, scientists have identified genes in “elite sleepers” that could lead to treatments for these types of neurodegenerative diseases.

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As part of this new research, carried out by scientists from Cambridge University and China's Fudan University, almost 500,000 adults aged between 38 and 73 years were analyzed. This included survey data on sleep patterns, mental health and wellbeing, and cognitive testing. Brain imaging data and genetic data were available for almost 40,000 people.

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As a result, scientists were able to gain new insights into sleeping habits in middle and older ages and brain health. Building on the results of a 2018 study, the analysis found that both too little and too much sleep have negative effects on visual attention, memory, problem-solving ability and processing speed. This also led to an increase in symptoms of depression and anxiety and poorer overall well-being.

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The scientists concluded that seven hours of sleep is optimal for brain health and that sleeping too much or too little may be a risk factor for age-related cognitive decline. The findings also support an idea explored in an interesting study from 2020, which established a link between deep sleep disorders and Alzheimer's disease.

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Previous research in animals and humans has shown that this type of fragmented sleep can increase the accumulation of toxic proteins associated with Alzheimer's disease. In addition, slow deep sleep is an important brain function that breaks down waste products and toxic proteins. This research paper from 2020 suggests that fragmented sleep could be an effective way to predict the risk of neurodegenerative disease.

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“Good sleep is important at all stages of life, but especially in old age,” said Professor Barbara Sahakian from Cambridge University. “Finding ways to improve older people's sleep could be critical to helping them maintain their mental health and wellbeing and avoid cognitive decline, particularly in patients with psychiatric disorders and dementia. ”