Sleep deprivation has been linked to hypertension, obesity and diabetes and has long been suspected of having a connection to dementia. Now, a large new study has more clearly established that association by concluding that people who sleep less than six hours a night in midlife have a greater risk of developing late-onset dementia.
That doesn’t mean middle-aged short sleepers should panic, according to experts. Although the study is an important step forward, much about the connection between sleep and dementia remains unknown, they said. Still, it can’t hurt to work on your sleep habits while research continues, and you’ll find some strategies listed below.
In the study, European researchers followed nearly 8,000 people in Britain for 25 years, starting when subjects were 50. They found that those who consistently got six hours of sleep or less per night in their 50s and 60s were about 30 percent more likely to develop dementia later in life, compared with those who logged seven hours of sleep per night. That was independent of “sociodemographic, behavioural, cardiometabolic, and mental health factors,” the study’s authors wrote. Findings were published in the journal Nature Communications in late April.
“This is just another example of the importance of appropriate sleep for brain health,” said Michael V. Vitiello, a professor of psychiatry and behavioral sciences at the University of Washington at Seattle and member of the sleepfoundation.org medical advisory board, who wasn’t involved in the study. “It’s really important for people to be conscious of making sure that they sleep well. It’s not trivial, and it shouldn’t be the last thing you think about. It shouldn’t be the thing you sacrifice.”
Lack of sleep might increase dementia risk by impairing learning and memory development, said study author Andrew Sommerlad, an old-age psychiatrist at University College London, or it could affect the brain’s ability to clear harmful protein waste products.
Researchers have spent years trying to understand the sleep-dementia connection, a quest that becomes more urgent as the number of people with Alzheimer’s disease balloons. More than 6 million Americans are living with the disease, according to the Alzheimer’s Association, and by 2050, that number is expected to reach nearly 13 million. Yet, it’s a difficult area in which to draw conclusions.
Earlier this year, Charles Czeisler, chief of the sleep and circadian disorders division at Brigham and Women’s Hospital in Boston, co-authored a similar study that found that adults age 65 and older who got five hours or less of sleep per night had double the risk of dementia than those who clocked seven or eight hours per night. Results were published in the journal Aging.
“At this point, it’s too early to say that behavior X leads to Y,” Czeisler said. “But the association certainly reveals the importance of continuing to study the relationship.”
One of the challenges to studying the link between sleep and cognitive decline is that it’s difficult to determine what happens first: Is too little sleep a symptom of the brain changes that often begin decades before cognitive problems appear? Or does it cause those changes? So far, that’s still unclear, said Claire Sexton, director of scientific programs and outreach with the Alzheimer’s Association.
“There’s mounting evidence pointing toward the relationship between sleep and dementia,” she said. “But there are a lot of unanswered questions. There’s no one factor that would guarantee someone will develop dementia, and there's no one factor that will guarantee someone won’t.”
Vitiello lauded the new study’s lengthy follow-up period and examination of people in their 50s. (Most similar research focuses on those 65 and older.) But he emphasized that the findings estimate increased risk for the entire population, not for any one individual. “These are predictions,” he said. “On average, if you have this kind of disturbed sleep, your odds go up this percentage. It doesn’t mean that just because you’re a 55-year-old sleeping under six hours a night, you’re guaranteed to have an increased Alzheimer’s risk of 30 percent.”
Exactly why someone is a short sleeper — for example, if they have insomnia, hold multiple jobs that require odd hours or naturally need less sleep — probably plays a role in their unique risk, he added. The study didn’t account for those factors.
Study author Séverine Sabia, an epidemiologist at Inserm, the French public health research center, acknowledged that her team’s findings only indicate an association between short sleep duration and dementia — not causation.
“Dementia is a multifactorial disease, which means that several factors are likely to influence its onset,” she said, including physical inactivity, smoking and social isolation. “Sleep duration is one of them, but even if a person has poor sleep, there are other important prevention measures.”
So, the takeaway for those with subpar snooze times? “No reason to panic,” Sabia said, pointing out that doing so might “worsen sleep quality,” but it’s a smart idea to work on getting better, longer sleep. Here are some strategies:
Be consistent. It’s best to wake up and go to bed at the same time every day on weekdays and weekends. Most importantly, “maintain your rise time, because that will partially set your going-to-bed time,” Vitiello said. He noted that there’s no need to force yourself into bed early, even if you have a special event the next day: “Biologically, your body is designed to sleep a certain amount, and if you extend your bedtime, it doesn’t guarantee you’re going to fill it with sleep.” You’ll probably toss and turn, wide-awake.
Make changes slowly. Like anything else, it can help to ease into healthy new habits. Jumping straight from, say, four hours of sleep a night to seven will be difficult for many people, Czeisler said. He recommends steadily increasing your sleep schedule by 15 or 20 minutes in the night and/or morning.
Develop a pre-sleep routine. Think of this as a ritual that helps you ease out of the day’s havoc and into a calm, sleep-inducing state. “You don’t want to just go directly from the evening news, and being depressed and anxious about it, to the bedroom,” Vitiello said. Different people will migrate toward different transitions — a book-lover might read, for example, though he recommends avoiding dramatic novels that could interfere with the ability to fall asleep. Others might take a warm bath or meditate.
Optimize your bedroom. Vitiello is based in Seattle — a high-latitude city that will soon experience light from around 4 a.m. to 10 p.m. So, if he were light sensitive, he’d install blackout curtains. Setting yourself up for optimal sleep also includes adjusting the room temperature to your liking, perhaps installing a white-noise machine and making your bed extra comfortable.
Cut back on artificial light. There are lots of tools that can help protect against exposure to blue light, which streams out of devices such as smartphones and computers and can disrupt sleep patterns. Various apps help to block blue light, and you can also dim the brightness on your phone.
Be mindful of lifestyle habits. Sleep is part of a healthy lifestyle, Vitiello said, along with following a healthy diet, getting enough exercise and paying attention to alcohol use. Alcohol might help you fall asleep more quickly, he said, but it can lead to a lower quality of snoozing. “I’m not saying you can’t drink a glass of wine before bed as part of your wind-down ritual, but if you feel your sleep is rocky in the second half of the night when you do that, then it’s not a good thing,” he said.
Prioritize it. Being aware of the importance of good sleep is often the most crucial factor to improving it; the key is not “being passive,” Vitiello said. And if you find you’re struggling to improve your slumber, or you don’t feel rested during the day? Talk to your doctor or set up an appointment at a sleep center. “Most sleep problems have a solution,” Vitiello said. “Not everything can be cured, but everybody with a problem can be helped.”
Angela Haupt is a writer and editor based in the District. Follow her on Twitter @angelahaupt