The number of people around the world with dementia is staggering -- and growing. The mind-robbing disease has no cure, but recent research is beginning to show how you may best be able to lower your chances of getting it.
"It's not yet definitive, but in the past 6 years, we've made progress on identifying modifiable risk factors for which the evidence is pretty strong," says Kristine Yaffe, MD, a professor of psychiatry, neurology, and epidemiology at the University of California, San Francisco.
At least one thing that makes dementia more likely -- getting older -- is unavoidable. But scientists say certain lifestyle choices may lower the odds in your favor. And while it's never too late to benefit from healthy changes in your life, studies show that starting early may mean extra protection decades later.
"Research from the past 2 to 3 years suggests that risk factors need to be focused on in midlife," says Keith Fargo, PhD, director of scientific programs and outreach at the Alzheimer's Association.
Consider high blood pressure. In a study published in 2017, researchers followed nearly 16,000 adults, ages 44 to 66, for 24 years. They found that people with high blood pressure in midlife had a nearly a 40% higher risk of dementia. A 2014 review of previously published studies estimated that midlife high blood pressure leads to as many as 425,000 cases of Alzheimer's disease in the U.S. each year. Fortunately, according to a 2018 study published in TheJournal of the American Medical Association that included nearly 9,500 adults age 50 or older, some evidence shows that controlling blood pressure could lessen the risk of mild cognitive impairment, a precursor to dementia.
"This is the first trial that has demonstrated an effective strategy for prevention of age-related cognitive impairment," Yaffe wrote in an editorial published with the study.
That said, you should pay attention to your health, no matter how young or old you are, says neurologist Douglas Scharre, MD, director of the division of cognitive neurology at Ohio State University's Wexner Medical Center in Columbus, OH. "If you have any dementia risk factor identified at any age, that is when you should be addressing or trying to control it."
The World Health Organization estimates that 82 million people worldwide will have dementia by 2030. In the United States, nearly 14 million will have Alzheimer's disease -- a leading cause of dementia
-- by 2050, more than double the current number, according to the Alzheimer's Association.
Dementia causes a slow decline in thinking skills. It affects memory, mood, language, and other things the brain controls. People with dementia eventually can’t live independently and require around-the-clock care and attention. Alzheimer's is the leading cause, followed by stroke and other conditions that damage blood vessels and can cause what's known as vascular dementia.
In addition to having a healthy blood pressure, evidence has been building that controlling other things that affect your heart health -- such as cholesterol and diabetes -- may lower your risk. In a study released last December, for example, researchers reported that type 2 diabetes appears to cause brain changes that could harm memory and other brain functions. Another from May 2018 found that cholesterol seems to encourage the buildup of proteins in the brain that are believed to play a major role in the development of Alzheimer's disease.
"Managing your blood pressure, your cholesterol, and, if you have it, your diabetes, will likely lower your risk of dementia later in life," says Jagan Pillai, MD, PhD, a neurologist with the Cleveland Clinic Lou Ruvo Center for Brain Health in Cleveland, OH.
Recent research also has pointed to other things that may contribute to brain health, including:
- Proper sleep
- The use of hearing aids, if needed
- Preventing head injuries
- Regular social interaction and other types of mental stimulation
The Link to Sleep
During sleep, the brain cleans house, flushing out toxic buildups of beta-amyloid, a protein that has been linked to Alzheimer's disease. Poor sleep makes it harder for the brain to do this janitorial work. Over time, the buildup of toxins may lead to dementia.
A study published in June 2018, which included 283 adults whose average age was 77, revealed a link between daytime sleepiness and higher amounts of beta-amyloid. And in a study published in 2017, researchers reported similar findings in 101 adults whose average age was 63. "We don't know exactly what explains the link between sleep and dementia, but it does seem that there is something about sleep and the clearing of beta-amyloid," Yaffe says.
New research also shows such buildups in humans. Two small studies -- one published in 2017, the other in 2018 -- showed an increase in beta-amyloid in people who got a single night's poor sleep. But, the author of one of the studies points out, experts worry more about chronic sleep problems than one night of tossing and turning.
There likely are other explanations as well. For example, Pillai says uncontrolled sleep apnea may cause numerous small strokes that lead to memory and thinking problems later in life. But recent research raises more questions than it answers. "A lot of the details are unclear regarding how sleep impacts Alzheimer's disease and dementia in general," Pillai says. And, says Yaffe, "We still don't know whether treating your sleep problems would decrease your risk of dementia."
Hearing and Social Stimulation
In 2017, a major report on dementia added hearing loss to the list of controllable things that can make the condition more likely. ("That's the most important development of the last year," Fargo says.) Right now, though, experts don't know what links hearing loss to dementia. The authors of the report suggest that hearing problems force the brain to work harder to understand what's being said. Over time, that extra burden may cause harm. Or the dementia may come from social isolation. If your poor hearing does not allow you to take part fully in conversations, you may lose the brain benefits that come from that type of mental stimulation.
Scharre agrees: "Most hearing loss occurs outside the brain and is not related to the brain, but if you're not getting input or socialization, that may affect the brain indirectly."
As with sleep, it's not yet known whether correcting hearing loss -- through the use of hearing aids, for example -- will cut the risk of dementia. But Fargo says mental stimulation, which includes interacting with others, appears to offer protection against dementia. "Social stimulation is huge," he says.
Protect Your Head
Head injuries also have been tied to dementia. In a study published in 2018, for example, researchers studied the health records of more than 164,000 people who'd had a traumatic brain injury (TBI). Serious injuries doubled the risk of dementia, while repeated injuries nearly tripled it. Even after more than 30 years, the risk remained 25% higher than normal.
Recent research also suggests that even mild head injuries make dementia more likely. Yaffe and her colleagues studied veterans who had had mild concussions but did not lose consciousness. Their findings, published in September 2018, reports that such injuries more than double the risk of dementia. More severe injuries boost the risk even higher.
Pillai points out that we can't say if Yaffe's results would apply to others besides veterans, but, he says, "it opens up a new area of concern." The relationship between head injuries and dementia makes sense. As Scharre puts it, "Head injuries can't possibly be helpful for the brain." But the link is complicated and not well understood. "Injury takes its toll, but we don't know all of the mechanisms," says Yaffe.
Genetics may play a role, too. One gene known to increase the risk of Alzheimer's disease, APOE4, may also contribute to a higher risk of dementia after a traumatic brain injury, according to a study published in September. "I truly believe that there's a huge impact from genetics," Scharre says. "Certain genetics likely make you much more prone to the effects of concussion, such that your brain is less able to heal, or the inflammatory condition that arises maybe goes overboard and causes more damage."
Eventually, tests might be able to identify people whose genes make it more dangerous for them to play football, a sport in which head injuries commonly happen. Scharre says that by that point, we may also know how to modify those genes to cut risk before the first hit happens.
In the meantime, though, avoiding injury is your best protection. "From a public health point of view, we need to prevent traumatic brain injuries," says Yaffe, who is now studying what makes some people more susceptible to dementia than others after a brain injury. "And if you've had one, you don't want to get another one. We think there's a cumulative risk."
More Questions to Answer
All of these things that raise the risk of dementia -- and more -- need to be better understood, and another question also must be answered: How do the risks relate to each other? And how might addressing those risks together influence the development of dementia?
For example, Yaffe says, if you go to the gym, you may not only be more physically active, but also more social, both of which are believed to help protect against dementia. That may also cut your likelihood of having depression, which some research has linked to dementia as well.
"We're starting now to do trials where we don't look at just one factor -- we try to look at risk factors together, because often they go together," says Yaffe. She just began a 2-year study of how a combination of things that raise your odds of dementia -- such as social isolation, sleep, and blood pressure, as well as diabetes, exercise, and certain medications -- can affect you.
Lessen Your Risks
- Get your heart going with frequent aerobic exercise like running, walking, or riding a bike. That may help protect the aging brain. "If you can, you want to get sweaty a few times a week," says Scharre.
- Eat right to protect your brain. Scharre recommends the MIND diet, which combines the heart-healthy Mediterranean diet with the blood pressure-lowering DASH diet. "Anything you can do to make better eating choices, you should do," he says.
- Keep your brain active, especially by involving others. Play strategy games like mah-jongg, bridge, and hearts; find volunteer opportunities; or simply engage people in conversation. "Social interaction is huge," says Scharre.
Don't wait. It's never too soon to begin buttressing your brain health, says Scharre: "Start early and do it continuously to protect your brain."
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