How much sleep keeps cognitive decline at bay?

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Too much or too little sleep can damage your brain, leading to memory and thinking disorders, suggests a study published online Aug. 30, 2021 JAMA Neurology. The researchers analyzed the brain images, cognitive test scores and self-reported sleep habits of more than 4,400 older men and women around the world. Sleeping six hours or less a night (short sleep) has been associated with impairments in cognition, primarily memory, as well as increases in amyloid beta — the protein that can form brain plaque (a hallmark of Alzheimer’s disease). Sleeping nine hours or more (long sleep) was also associated with cognitive problems, particularly in decision-making. And both short and long sleeps were associated with higher body mass index (a measure of body fat), more depressive symptoms, and more naps compared to people who got seven or eight hours of sleep. The study was observational and can’t prove causality, but the results echo many other studies that suggest too little — and possibly too much — sleep causes cognitive problems.

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