While eight hours of sleep is great for growing bodies, people who have reached middle age might get more benefits from sleeping just seven hours a night, according to new research.
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What's more is the study, conducted by UK Biobank, found that seven hours is a hard number; meaning that sleeping less or more than that can reduce a person's ability to pay attention, learn, solve problems and make decisions, researchers say.
"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," says Jianfeng Feng, one of the study's authors. "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."