Whether our minds stay sharp as we age may depend on how much rest we get, a new study suggests.

For the study, published April 28 in Nature Aging, scientists examined data on almost 500,000 adults ranging in age from 38 to 73 who were part of the UK Biobank, an ongoing government-funded research project. All the participants were asked about their sleep habits and mental health and well-being, and they also completed a series of cognitive tests to assess brain function. A subset of about 40,000 people also had brain scans and lab tests to collect genetic information.

People who got about seven hours of sleep each night had better cognitive outcomes than other participants, the analysis found. Longer or shorter periods of sleep each night were associated with a reduced ability to make decisions, solve problems, pay attention, process information, and learn new things.

Seven hours a night was also ideal for mental health, the study found. Too much more or less sleep than this was associated with more symptoms of depression and anxiety and worse overall well-being.

“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 the senior study author, Jianfeng Feng of Fudan University in China, in a statement.

“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,” Feng said.

Brain scans showed that people who got about seven hours of sleep each night had fewer structural changes in regions of the brain associated with cognitive processing and memory than study participants who got too little or too much sleep.

In addition, participants who consistently got about seven hours each night, without too much deviation from this pattern, had better cognitive function and mental health than people whose sleep patterns varied a lot or who got excessive or insufficient amounts of rest.

Sleep plays an important role in cognitive function and good psychological health. It also helps keep the brain healthy by removing waste products that can contribute to the development of dementia and Alzheimer’s disease.

It’s common to develop sleep problems as we age, including difficulty falling asleep and staying asleep, as well as reduced quantity and quality of sleep.

Previous research has found that middle-aged and older adults who suffer from insomnia or other sleep disturbances are at increased risk of cognitive impairment. Earlier studies have also found that people who struggle to fall asleep or get insufficient or poor quality sleep are more apt to experience cognitive decline and dementia than people who nod off as soon as their head hits the pillow and sleep soundly all night.

Adults need at least seven hours of sleep each night for optimal health and well-being, according to the Centers for Disease Control and Prevention (CDC). Slightly more than one-third of adults get less than seven hours of sleep, which is associated with an increased risk of a wide range of chronic health problems including obesity, heart disease, asthma, diabetes, and depression.

“Getting a good night’s sleep is important at all stages of life, but particularly as we age,” says a coauthor of the study, Barbara Sahakian, DSc, of the psychiatry department 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 avoid cognitive decline, particularly for patients with psychiatric disorders and dementias.”

EPILYNX SKINCARE TIP: sleep is not only great for your internal and mental state but is also great for the health and glow of your skin!