Q&A: Dr. Eric Larson on Ways to Lower Dementia Risk—and Why They Work

Lifestyle changes can lower our dementia risk. Dr. Eric Larson, senior investigator at Kaiser Permanente Washington Health Research Institute, dives into the science to help explain just why diet, sleep, physical activity and other factors have such a big impact on brain health. This conversation is part of the Being Patient LiveTalks series.

Certain risk factors of dementia, from our genetics and family history to our age — are beyond our control. However, there are steps that we can take — as individuals and as a society — to reduce our chances of developing dementia and improve our overall brain health. In fact, research has shown that controlling things like education, air pollution, diet, sleep, exercise and social isolation can potentially help postpone or prevent as many as 40 percent of dementia cases. 

Being Patient spoke with Dr. Eric Larson, senior investigator at Kaiser Permanente Washington Health Research Institute, about the controllable lifestyle factors linked to dementia, why these links exist, and how to monitor and boost our brain health and reduce our chances of developing the illness.

Being Patient: Dr. Larson, you are the co-author of the report by the Lancet Commission on dementia prevention, intervention and care, which identified various risk factors throughout life that are linked to dementia. So, to what extent are we actually in control of preventing dementia? 

Dr. Eric Larson: That’s a $64,000, maybe $64,000,000, question. It’s debated, but we concluded that it’s plausible that perhaps up to 38 or 40 percent of the risk that a person has of getting dementia could be modifiable … [There’s] a series of events [that] when added together could reduce your risk of dementia or Alzheimer’s disease. 

Being Patient: How did you and your colleagues come to that conclusion? 

Dr. Eric Larson: The study took what’s called a life course approach and reviewed probably thousands of papers. A staff at the University College of London did all this research and there were 20 or so of us international experts who gathered to come up with what’s called a Lancet Commission report. There’s a really interesting rainbow diagram of these little streams from early life [and] midlife [to] late life, and based on the evidence, we tried to assign the percent of risk that would be lowered if, in fact, these modifiable risk factors are modified. When you add them together, if they are truly arithmetically addable, [there’s] a 38 to 40 percent potential reduction. It’s very theoretical, but I think it’s good enough information to act on as an individual and in terms of developing social policies.

Being Patient: Was there one particular area that surprised you the most?

Dr. Eric Larson: I was not expecting to see that much of a change related to reversing hearing loss. That was a surprise. The other surprise was how many of the things that we think are beneficial to reduce risk for Alzheimer’s disease are beneficial to reduce risk of not being healthy like habitual exercise, controlling blood pressure, not being too far out of line with your blood sugar and so forth.

Being Patient: Why is hearing loss a dementia risk factor? 

Dr. Eric Larson: There are at least two possibilities. One is that hearing loss isolates you and social stimulation seems to be valuable to prevent cognitive decline. The other potential is that hearing loss is caused by Alzheimer’s disease. We know that there’s a type of hearing loss, which is distinguishing sound from noise. That’s a complicated cognitive function and that may be the most important marker and it may well be that that’s intrinsic to the disease itself. There’s a lot of open questions around hearing loss, but it’s really clear that if you have it, it’s wise to try to correct it. 

The study in The Lancet was really a compilation of research from around the world. In general, there’s some evidence that correcting hearing loss reduces the rate of cognitive decline, and it also clearly improves a sense of wellbeing and avoids depression. 

Being Patient: Are we headed to the direction where we can monitor our daily health to better understand how the biology of our bodies could impact the brain? For instance, people use glucose monitors to keep track of their glucose levels.

Dr. Eric Larson: I do. There’s a movement called the ‘measured self’ … There are anecdotes of people who detect an uptick in their glucose level, [then] they change their diet or exercise and it goes back down. If we know that the higher the glucose, the greater the risk of Alzheimer’s, then you’re probably doing something if you measure that and can act on it. 

The key is to act on it. People that count their steps every day, or whatever measure of physical activity, can measure that and act on it. If you find that you’re not reading well at night because of your sleep, [for example], or you’re having disordered sleep because you drank too much after dinner some night, those are the kind of things you can actually probably act on. 

Being Patient: What questions should we be asking to monitor our brain health? 

Dr. Eric Larson: It’s hard to answer as precisely as I’d like to. For example, I don’t think people are recommending screening for hemoglobin A1C unless there’s a reason for it. But it’s a reasonable thing, if you think you’re wanting to do everything, to possibly check your A1C. It’s a reasonable thing to check your waist circumference ratios and see if you have gone the wrong direction. That’s another measure that correlates with insulin resistance and and adverse events. 

Some other things are just simple physical activity and making sure that you’re getting at least the minimum level of physical activity that’s recommended. If you’re completely inactive, just getting up to 15 minutes a day most days of the week will reduce your risk. 

Being Patient: What is insulin resistance and why is it bad for our brain health? 

Dr. Eric Larson: A lot of these mechanisms are not known precisely, but insulin resistance means it takes a larger amount of insulin from your pancreas to keep your blood sugar in the normal range. When you produce more insulin, it’s believed that that has a direct toxic effect on the brain, or if it’s not working well enough to keep glucose or blood sugar down, [the] same thing [happens]. It probably has to do with oxygenation, if you will, and damage due to oxidative events in the brain that are reduced in the state where you have less levels of insulin to control the blood sugar. 

Being Patient: If you have already been diagnosed with dementia, could lifestyle changes still help? 

Dr. Eric Larson: I think you can change the trajectory. I don’t know if you can change the molecular events in the brain that are behind a person’s disability. But we did a study years ago, led by my colleague Linda Teri and published in Journal of the American Medical Association (JAMA), and we show that for pairs, if you set up a program where they walk regularly and also [where caregivers receive training in] some behavior techniques, the people (patients) that got the treatment in the randomized trial experienced less physical decline and were less likely to need to go to a skilled nursing facility for behavior changes. I think as long as you’re able to do it safely, regular exercise probably affects the course of the disease.

“It’s very likely that there’s not just one type of
Alzheimer’s disease. If there are different types and
we can understand them better, then either the lifestyle
changes or the treatment that one could offer would be
more informed. There [are] huge opportunities
for research in this field right now.”

Being Patient: How important is sleep for reducing dementia risk? 

Dr. Eric Larson: We believe that sleep is an area of importance. It’s clear that people with disordered sleep or a lack of sleep are at higher risk. We don’t know exactly how that works. There’s a system called the glymphatic system which seems to be important for draining toxins. I think we’ll learn more about that in a few years, but common sense indicates that if you sleep too little or a lot, you’re at higher risk. 

The thing about sleep that I’d like to emphasize is that the over-the-counter medications that people take for sleep are actually very likely — if they’re taken at too high a dose or too often — to pretty dramatically increase the risk of cognitive decline and also the risk of falling and other things if you’re having a soporific effect of a sleep medication.

Being Patient: What areas do we need to explore more to better understand the link between lifestyle choices and Alzheimer’s risk?

Dr. Eric Larson: There’s probably a spectrum of areas that you want to understand better, [including] knowledge about behavior change. What is it that motivates people to exercise more, or to control their blood sugar or maybe not drink so much alcohol or control their blood pressure? That’s one level of area of research and we don’t know a lot about that. Is it better to work one-on-one with a counselor or through social media campaigns? 

Then … how do these risk factors work in the first place? How is it that hearing loss is somehow associated with the disease? Is it the disease itself that’s causing the hearing loss or is it just the lack of sensation to the brain and the isolation [from hearing loss that’s linked with the disease]? Those are the kinds of things that research can study, and the same thing [goes for] the disease itself. 

It’s very likely that there’s not just one type of Alzheimer’s disease. If there are different types and we can understand them better, then either the lifestyle changes or the treatment that one could offer would be more informed. There [are] huge opportunities for research in this field right now.