This many hours of sleep can help avoid Alzheimer's and anxiety

A recent study found that too little and too much sleep were both associated with cognitive impairment, including lapses in attention, memory and problem-solving skills.

Dave Yasvinski 3 minute read May 3, 2022
3d rendering of an old-fashioned alarm clock on a fluffy white cloud on a blue background.

Too much or too little sleep may be a risk factor for age-related cognitive decline. GETTY

Seven hours of sleep per night is the sweet spot for middle-aged and older adults, according to a study that found any more or less was tied to cognitive impairment and poorer mental health.

The study, published in the journal Nature Aging, concluded that insufficient and excessive sleep were both associated with aspects of cognitive impairment, including lapses in processing speed, visual attention, memory and problem-solving skills. A solid seven hours proved to be the optimal duration to maximize cognitive performance and avoid the symptoms of anxiety and depression that can accompany an unsatisfying slumber.

“While we can’t say conclusively that too little or too much sleep causes cognitive problems, our analysis looking at individuals over a longer period of time appears to support this idea,” said Jianfeng Feng, one of the authors of the study and a professor at Fudan University in China. “But the reasons why older people have poorer sleep appear to be complex, influenced by a combination of our genetic makeup and the structure of our brains.”

Sleep plays a vital role in cognitive function by removing waste products and helping to sustain good psychological health. As people age, studies have shown sleep patterns can fluctuate and the quality and quantity of rest can decline. It is believed these fluctuations can contribute to cognitive decline and the emergence psychiatric disorders in older populations.

They explore the issue, researchers analyzed health data from around 500,000 adults between the ages of 38 and 73 included in the UK Biobank and recruited another 40,000 subjects to talk about their sleep patterns, mental health and well-being. Genetic data and brain imaging were available for most of the latter group, which also participated in a series of cognitive tests.

The team concluded that seven hours of sleep per night was the ideal amount of rest to maximize cognitive performance and enhance mental health, with symptoms of anxiety and depression worsening in subjects who reported longer or shorter periods of rest. They speculated that this association may be due to the disruption of slow-wave (or deep) sleep that has a close relationship with memory consolidation and the buildup of amyloid, an important protein that can, in some instances, misfold and cause “tangles” similar to some forms of dementia.

Link between how long you sleep and memory

Researchers also detected a relationship between sleep duration and differences in the structure of areas of the brain that play a part in cognitive processing and memory, with greater changes tied to getting more or less than seven hours of sleep. Previous studies have shown that interrupted sleep patterns are also associated with an increase in inflammation, a development that can increase susceptibility to age-related disease.

Ultimately, the team concluded that too much or too little sleep may be a risk factor for age-related cognitive decline, pointing to research that has linked sleep duration to the risk of developing Alzheimer’s disease and dementia.

“Getting a good night’s sleep is important at all stages of life, but particularly as we age,” said Barbara Sahakian, one of the authors of the study and a psychiatry professor at the University of Cambridge. “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.”

Dave Yasvinski is a writer with Healthing.ca

Thank you for your support. If you liked this story, please send it to a friend. Every share counts.