By Wendy Haaf
You obviously can’t control every risk factor, but there’s a lot you can do to reduce your chances of getting dementia.
According to a 2021 survey, 49 per cent of UK adults say dementia is the health condition they fear most—among those over 65, that number jumps to 65 per cent. Their concern is hardly surprising: while only 11 to 15 per cent of people 65 or older will ever develop dementia, existing treatments offer only modest benefits, if any, and the disease is still a leading reason for admission to a nursing home.
However, a growing body of research suggests that “a big chunk of the risk is in our hands,” says Nicole Anderson, director of the Ben & Hilda Katz Interprofessional Research Program in Geriatric and Dementia Care and associate director of the Kimel Family Centre for Brain Health and Wellness at Baycrest Health Sciences in Toronto.
Based on a comprehensive 2020 review by the 28-member Lancet Commission on dementia prevention, intervention, and care, “12 potentially modifiable risk factors accounted for about 40 per cent of dementia cases worldwide,” Anderson says. And that may be a conservative estimate. For example, there’s good evidence that a Mediterranean-style diet is associated with reduced dementia risk, but the authors concluded that the available data wasn’t sufficient to include in their calculations, even though they “believe [dietary factors] could be important.”
While the number one culprit — lack of secondary education in early life — is something you can’t change, if it applies to you, don’t despair. “Think of it as a teeter-totter,” Anderson says. “You can still do other things to reduce your risk.” Another way to look at the equation is that each of the following shores up your cognitive reserve—your brain’s ability to resist and compensate for various types of damage.
Here’s a rundown of measures that, based on the Lancet report, could help tip the teeter-totter in your favour.
Treat sensory losses
Hearing loss isn’t simply a modifiable risk factor for dementia—it tops the list for adults aged 45 to 65, accounting for an estimated nine per cent of total cases.
“It’s not entirely understood what the real link is, but having that loss of sensory input to the brain seems to increase the risk for onset of cognitive impairment,” notes R. Jane Rylett, scientific director of the Canadian Institutes of Health Research (CIHR) Institute of Aging and a distinguished professor in the Department of Physiology and Pharmacology at Western University’s Schulich School of Medicine & Dentistry in London, Ont. Hearing loss can also lead to social isolation, which itself has been strongly linked to dementia risk.
Whatever the reasons, “there is accumulating evidence that hearing aids can make a real difference,” Rylett says. (Of course, it’s also important to protect your hearing by avoiding exposure to loud noise or using noise-blocking plugs or earmuffs.)
Clearly, we have to start viewing hearing loss more as we do vision loss. “Nobody has a problem wearing glasses, but many people still feel uncomfortable about wearing a hearing aid,” Anderson observes. What’s more, even when people do get treatment for hearing loss, many may miss out on the brain benefits. Unlike glasses, “hearing aids take a good six months to get used to and adjust, so people need to stick with them for the long haul,” she adds.
Vision loss hasn’t yet been added to the Lancet Commission’s list of modifiable risk factors, but it may only be a matter of time. University of Michigan researchers who analyzed data from that state’s Health and Retirement Study estimated that nearly two per cent of dementia cases in the United States may be due to vision impairment and loss—80 to 90 per cent of which is avoidable through early detection and treatment.
Protect against traumatic brain injury
By reducing your risk for traumatic brain injury, simple measures such as wearing your seatbelt may help decrease your dementia risk, too.
To illustrate the point at public talks, Anderson shows a photo of adults and a child riding bicycles in which the youngster is the only one wearing skull protection. “Your brain is as important as your grand- child’s,” she stresses. “Wear a helmet.”
While we’re on the subject of safety, you may want to ensure that you get your annual flu shot and take precautions, including immunization, against contracting COVID-19. Recent research suggests they may pro- tect against more than just the viral infections. A June 2020 study that followed nearly 1.9 million US adults aged 65 or older found that those who had received at least one flu vaccine were 40 per cent less likely than their unvaccinated peers to develop Alzheimer’s disease within four years. One possible explanation is that flu causes inflammation, which is associated with subsequent dementia.
The results of a separate study released in the same month are similarly striking. Researchers followed 919,731 Danish adults who underwent COVID-19 testing between February 2020 and November 2021; among those who tested positive (43,375), there was a 3.5-fold jump in the inci- dence of being diagnosed with Alzheimer’s disease compared to the inci- dence among participants with negative results. They were also far more likely to suffer an ischemic stroke (3.5 times) or bleeding in the brain (4.8 times), both of which substantially increase the risk for dementia. (COVID-19 can potentially cause blood clots—the cause behind ischemic stroke—not just during infection but up to six months afterwards.)
Prevent or manage hypertension and diabetes
What’s good—or bad—for your heart and blood vessels similarly affects the health of your brain. Poor control of high blood pressure or diabetes, for example, “increases the risk of not only vascular dementia but also Alzheimer’s disease worsening and progressing more quickly,” Anderson says.
Hypertension is a leading cause of stroke, “and we know that once you have a stroke, your risk for dementia, particularly vascular demen- tia, is actually twofold,” notes Teresa Liu-Ambrose, professor and Can- ada Research Chair at the Djavad Mowafaghian Centre for Brain Health in Vancouver.
The Lancet Commission’s review found that hypertension was the third leading preventable risk factor in mid-life adults (aged 45 to 65 years), while diabetes was considered fifth in late life (after age 65). For those in the former group, the authors recommend aiming to main- tain a systolic blood pressure (top number) of 130 mm Hg or less from around age 40.
Limit alcohol use
In 2020, excessive alcohol use was one of three modifiable risk factors “with new, convincing evidence” for dementia that the Lancet Commission added to its 2017 list. In addition to increasing the risk for medical conditions that are tied to dementia risk, such as high blood pressure, heavy alcohol consumption can damage the brain—by, for example, withering the areas involved in long-term memory.
Accordingly, the Lancet report recommends limiting intake to fewer than 21 units (one unit is equivalent to a small glass of wine) per week, although that’s much higher than the suggested ceiling in guidelines aimed at lowering risk for other diseases, such as cancer.
If you’re still smoking in late life, it may be tempting to think it’s too late to quit now, but, believe it or not, that’s not the case. According to a 2015 analysis of 37 studies, current smokers are 30 per cent more likely to develop dementia from any cause and 40 per cent more likely to end up with Alzheimer’s disease than are never-smokers. Yet even if you’re over 60, stopping reduces this risk. In a study of 46,140 men in this age group, those who had quit and stayed smoke-free for four years or more saw a significant drop in dementia risk over the subsequent eight years.
So if you smoke, consider talking with your doctor or pharmacist about evidence-based cessation options, such as nicotine patches and medications. According to the American Heart Association, these can double to triple a person’s chances of quitting successfully.
Defend against depression
“Another factor they talked about in the Lancet report as being important to address overall risk is late-life depression,” Liu-Ambrose says.
While depression is linked with an increased risk for subsequent de- mentia, it’s still not entirely clear whether the former is an early warning sign of the latter or if depression symptoms are caused by dementia- related damage that takes place decades before the dementia makes itself known, or both. However, growing evidence suggests that some of the brain changes linked with depression, which could in turn trigger or accelerate the development of dementia, may be reversed or halted by treating the mood disorder. For example, in animal studies, two differ- ent antidepressants boosted levels of a substance that nurtures the development of new brain cells and is depleted in depression.
Consequently, it makes sense to take steps to reduce your risk for developing depression. “Things like adequate sleep, healthy diet, social connections, and exercise have a huge impact on mental health and mitigate against a number of health issues as we age,” Rylett says. In particular, Liu-Ambrose adds, “we know exercise has a fairly robust effect on mood.”
Stay socially connected
According to the Lancet analysis, social isolation is nearly as great a risk factor for depression as smoking. In a Japanese study of 13,984 adults aged 65 or older, after 10 years of follow-up, 46 per cent fewer of those who’d scored highest on a five-point scale of social engagement (taking into account factors such as con- tact with friends and participation in community groups) went on to develop dementia than did participants with the lowest scores.
Social connections probably reduce susceptibility to dementia in a variety of ways, from strengthening brain networks and blunting the release of potentially harmful stress hormones to helping fend off depression.
However, there’s no question that a number of factors, such as impaired mobility and vision loss, can make it more difficult to get out and interact with people. That’s why Rylett and her colleagues at the CIHR Institute of Aging are “interested in evaluating the implementation of pro- grams that help people find the right place for them to be, with the support systems they need to improve their quality of life, perhaps by facilitating more social inter- action, physical activity, or better quality of diet.” For instance, in some circumstances, remaining at home alone may “not necessarily be the best thing because it can be very isolating.” She cites the example of a visually impaired family member in faltering health who began thriving after moving to a retirement residence.
Along similar lines, the Kimel Family Centre for Brain Health and Wellness will soon be opening “the first research-driven community centre that is focused on reducing dementia risk,” Anderson says. Participants will undergo “a deep dementia risk evaluation, including genetic risk factors, and other things research has shown relate to dementia risk, like stress,” she explains. Each person will then be pre- scribed activities tailored to address their individual risk factors. “For example, if they’re not getting enough exercise, we have a gym and a warm-water pool, and if they need stress reduction, we have a room with soft flooring for yoga and meditation.” Researchers will then follow participants over time.
Anderson is also involved in a trial examining the impact of a web-based program aimed at reducing dementia risk factors. (Called CAN-THUMBS UP, the study is an initiative of the Canadian Consortium on Neurodegeneration in Aging.)
“People will fill out questionnaires about their risk in different domains and then prioritize domains where they’re at moderate or high risk,” she says. “Then they’ll see relatively more content for those priority areas and set goals of ways to address the risk—such as, ‘I will walk four times a week for half an hour.’ It’s available in French and English, and people get four what we call ‘episodes’ a week that are 10 minutes long, with little quizzes throughout.”
The the current study is limited to 350 participants, but after it wraps up around September 2023, “the program, called Brain Health PRO, will be made freely available to all Canadians,” Anderson says.
Researchers have identified multiple ways in which physical activity and exercise may bolster our resistance to dementia. First of all, it attenuates the risk for conditions that increase the odds of developing dementia, such as high blood pressure and diabetes. Aerobic exercise helps increase brain volume (which tends to shrink with age) and both grey and white matter—all of which correlate with robust brain health. It also significantly increases blood levels of a growth factor that promotes the germination and sur- vival of new nerve cells in the brain.
Resistance exercise has also been shown to exert beneficial effects on the brain. For example, research by Liu-Ambrose and her colleagues found that older women who did resistance training exercises (including mod- erate weightlifting) twice weekly experienced less shrinkage in white matter than participants who did the same routine once a week.
More recently, scientists have discovered that when the muscles contract during exercise, “they release things we call myokines, which travel within the bloodstream and communicate with other organs, including the brain,” Liu-Ambrose says. One such myokine is irisin, which, among other things, may help protect brain cells against injury induced by restricted blood (and thus oxygen) flow. “We’re just beginning to realize that there’s this whole other level of communication,” she says, adding that it’s shedding light on why “exercise has such a magnitude of benefit.”
And, in fact, a growing body of research suggests that exercise not only helps slow or stop the slide into dementia but can even partially restore thinking and memory after these abilities have declined.
In a recent study, Liu-Ambrose and her team recruited people who had experienced stroke and who, “on average, had some degree of cognitive impairment on their baseline scores,” she explains. Participants were randomly assigned to follow one of the following regimens for six months: twice-weekly exercise sessions; light exercise plus educational seminars; or “cognitive enrichment, which included things like computerized cognitive training as well as more interactive cognitive activities such as improv,” Liu-Ambrose says.
When participants were retested at the end of the study, “after the intervention specifically with exercise, members of that group actually had less cognitive impairment,” she says. Moreover, she adds, “the degree of improvement we observed was deemed clinically important, such that it likely had impacts on their day-to-day function. Improvements on cognitive scaling correlated to improvements in their activities of daily living, such as the ability to handle finances.”
Perhaps the most hopeful message of all comes from a systematic review and meta-analysis carried out by Liu-Ambrose and her colleagues looking at whether exercise benefits people already living with dementia. “We found that there seem to be robust effects,” she says. “And the second part, which I think is quite good news, is that the benefit exists regardless of the type of dementia.”