Getting enough sleep is important for all kinds of reasons: Our bodies and brains simply function better when we’re well-rested. “Sleep affects almost every tissue in our bodies,” Michael Twery, MD, told the National Institutes of Health (NIH). “It affects growth and stress hormones, our immune system, appetite, breathing, blood pressure, and cardiovascular health.” Neuroscientist Merrill MitlerMD, adds: “Sleep services all aspects of our body in one way or another: molecular, energy balance, as well as intellectual function, alertness, and mood.”
The amount of rest we need each night, however, varies from person to person. While some might feel fine with just six hours of shut-eye, others need a full eight—or even more—to feel like they’re functioning at their best. A recent study, however, raises a red flag about the link between getting a certain number of hours of sleep per night and the risk of developing dementia down the road. Read on to find out what amount of sleep experts say could put you in the danger zone.
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More than 55 million people around the world are currently living with dementia, and close to 10 million new cases are diagnosed each year, according to the World Health Organization (WHO). Early symptoms may include forgetfulness, losing track of time, and getting lost in places you’ve been many times before, their experts write. As the condition progresses, people with dementia will experience increasing difficulty communicating and caring for themselves, and eventually, they will become unaware of where they are, behave erratically, and have difficulty recognizing loved ones.
Dementia may be the result of Alzheimer’s disease—which is the leading cause of the condition—or it may stem from a stroke, traumatic brain injury, or other disease. Sometimes the exact reason for dementia is unknown. Whatever the cause, the WHO says, dementia is the seventh-leading cause of death worldwide, and there is currently no cure for it.
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If you’re worried about your cognitive function and want to stay sharp for as many years as possible, getting good rest is one of the best things you can do for your brain. “Loss of sleep impairs your higher levels of reasoning, problem-solving, and attention to detail,” Mitler told NIH. “The fact is, when we look at well-rested people, they’re operating at a different level than people trying to get by on one or two hours less nightly sleep.”
Studies have linked common sleep issues such as snoring and sleep apnea with an increased risk of dementia, so if you struggle with either of those, it’s crucial that you speak with your doctor about how best to address and resolve them.
While getting plenty of sleep is important, two relatively recent studies have raised concerns about sleeping too much and what it could mean for your cognitive health.
A Feb. 2020 study published in the journal Alzheimer’s and Dementia found that sleeping for longer than nine hours each night was linked to decreased memory and difficulty learning—both of which are harbingers of dementia. “Insomnia and prolonged sleep duration appear to be linked to a decline in neurocognitive functioning that can precede the onset of Alzheimer’s disease,” the study’s lead author, Alberto R. RamosMSPH, said in a press statement.
An earlier study, published in the Feb. 2017 issue of Neurology, found that older adults who slept more than nine hours a night—but who had only recently begun slumbering for so long—were more than twice as likely to develop dementia a decade later. However, researchers said they weren’t sure if the excess shut-eye was to blame for the dementia diagnosis, or was merely a symptom of cognitive decline already beginning to take hold.
“We’re not suggesting you go wake up Grandpa,” Sudha SeshadriMD and senior author of the study, said in Neurology. “We think this might be a marker for the risk of dementia, not a cause.”
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While the prospect of potentially developing dementia is certainly scary, it’s important to understand that certain lifestyle habits could help keep it at bay. Things like getting regular exercise and eating a diet rich in fruits, vegetables, whole grains, and unsaturated fats can help, according to the NIH’s National Institute on Aging. Managing your blood sugar and maintaining a healthy weight can help too, as can treating hearing problems—if you’ve been told you need hearing aids, wear them—and staying connected with friends and family. And of course, getting plenty of sleep—but maybe not too much sleep—will help keep you on your toes, as well.