The following is a guest post from Dr. Tommy Wood (@drtommywood), associate professor of pediatrics and neuroscience at the University of Washington, where his research focuses on brain health. 

In this blog post, Tommy covers:

• Why B vitamins and Omega-3s work as a pair (not independently) to slow brain aging, plus the lab numbers to use as goals
• Air pollution, water contaminants, PFAS, and microplastics—what the evidence actually says, plus a few simple “set it and forget it” fixes
• The key role of oral health and products that are easy to integrate
• The 20-year study behind processing speed training, and why Super Mario and StarCraft aren’t just for kids
• Why sensory loss and accumulated illness may be stealth drivers of cognitive decline, and why the shingles vaccine keeps showing up in dementia research
• Why sleep remains one of the clearest modifiable risk factors for dementia, plus lesser-known strategies involving glycine, light therapy, and hemoglobin testing
• And much more 

Tommy’s new book is The Stimulated Mind: Future-Proof Your Brain from Dementia and Stay Sharp at Any Age.

Enter Tommy…

“The era of preventive neurology has arrived.” —The American Academy of Neurology, 2023.¹

Over the past 5–10 years, there has been a notable shift in how we think about cognitive decline and dementia, from a predestined inevitability to something that we might be able to prevent at both the individual and population levels. Current estimates suggest that at least 45% of dementia cases may be preventable, though there are many scientists in the field who feel this is a conservative underestimate. That 45% comes from the most recent iteration of the Lancet Commission on Dementia Prevention, which looked at the effects of 14 modifiable dementia risk factors—low education, hearing and vision loss, high LDL cholesterol, brain trauma, physical inactivity, diabetes, smoking, high blood pressure, obesity, excessive alcohol, social isolation, depression, and air pollution.² Other studies suggest that more than 70% of dementia may be preventable when including risk factors not considered in the Lancet analysis,³ with at least half of preventable cases seeming to be related to modifiable factors in our lifestyles and the environment. This means that we may have significant capacity to modify our individual risk of cognitive decline.

In this article, I’ll cover some lesser-known and emerging modifiable risk factors for cognitive decline and dementia. The big rocks of lifestyle will always be critical, but several additional interventions are increasingly worth looking at, due to their relatively low effort and big potential for long-term impact on brain health. For each intervention, I’ll include low-lift strategies you can consider adding to your brain-health toolkit to minimize the risk of cognitive decline and dementia.

The B Vitamin and Omega-3 Connection

One notable factor missing from the Lancet report that garnered both formal academic commentaries and mainstream media was nutrient status—specifically, homocysteine-lowering B vitamins (mainly B12 and folate [B9] but also B6 and riboflavin [B2]) and Omega-3 fatty acids.^8,9 One reason for the omission may be that it’s hard to isolate the benefits of these nutrients individually. Unlike an individual risk factor like smoking, there is less evidence for B vitamins and Omega-3s individually because they’re both required to see benefit.

The first study to find this interaction was VITACOG, which randomized participants with elevated homocysteine to a B vitamin supplement containing B12, folic acid, and B6.¹⁰ This resulted in slowed brain atrophy and cognitive decline. In particular, this benefit was only seen in participants who had adequate Omega-3 status.¹¹ Since then, multiple randomized trials have found the same—either that the benefit of B vitamins depends on Omega-3 status or that the benefit of Omega-3 supplementation depends on having adequate B vitamins status (i.e., not having high homocysteine).^12,13 Though I think it’s probably an overestimate, one meta-analysis even suggested that Omega-3 intake and homocysteine levels each contributed more than 20% of modifiable dementia risk.¹⁴

In studies of homocysteine lowering with B vitamins, the most benefit is seen when keeping homocysteine under 13 μmol/L, but a variety of other lines of evidence suggest that less than 10–11 μmol/L is probably better.¹⁵ Studies examining the relationship between Omega-3 status and risk of cognitive decline or dementia suggest that we should aim for an Omega-3 Index (percentage of Omega-3 fats in red blood cells) of at least 5%, with lowest risk in those above 8%.^16-18 If you’re not sure if you would benefit from additional intake or a supplement, most primary care physicians will measure homocysteine and potentially Omega-3 status as well. OmegaQuant offers an at-home Omega-3 Index test. The at-home DRIfT test includes Omega-3 Index as well as homocysteine, HbA1c, and Vitamin D.

Strategies to get adequate B vitamins and Omega-3s

Test plasma homocysteine (serum is acceptable but can show falsely elevated levels if not processed properly) and supplement if needed. If homocysteine is elevated (above 11 μmol/L), consider the doses used in VITACOG—800 mcg folic acid (or 1,360 dietary folate equivalents, DFE) and 500 mcg B12. Some studies lowering homocysteine with B vitamins have also included around 20 mg of B6 and 1–2 mg of riboflavin per day. Omega-3 status can be improved through regular seafood consumption, though supplementation can be worthwhile in those who don’t. Aiming to average 2–4 grams of long-chain Omega-3s (a combination of EPA and DHA) per day is a good target. Good options for homocysteine-lowering B vitamin supplements include Thorne Methyl-Guard (2 capsules/day), Pure Encapsulations MethylAssist (1 capsule/day), and Designs for Health Homocysteine Supreme (1 capsule/day). For Omega-3s, I generally recommend Nordic Naturals Ultimate Omega 2X, Parasol Omega-3, or Momentous Omega-3.

The Toxins in Your Air, Water, and Food

It often feels like our world is becoming increasingly toxic… in many ways. But even if we only focus on environmental exposures and dementia risk, there are a few important modifiable factors that come to mind.

Air quality
Included as a modifiable risk factor on the Lancet Commission’s list, several recent studies have found that air pollution from roads, local industrial activity, or wildfires can increase the risk of dementia.¹⁹ Inhaling tiny particles, nitrogen oxides, and ozone that are released into the air can trigger inflammation and oxidative stress as well as physiological stress.²⁰ While it can be impossible to escape the air around you without completely and permanently relocating, a measured approach would include wearing a mask when you’re outside on very smoky days—for instance, during wildfire season (an N95 mask will filter out the 2.5-micron particles thought to be particularly problematic).

It’s also important to recognize that the air inside can often be several times worse than the air outdoors.²¹ A high-leverage intervention could therefore be to get an air purifier for spaces where you spend a lot of time. For example, a recent study in healthy adults found that an indoor HEPA air filter significantly reduced blood pressure—another well-known risk factor for dementia.²² Though there is wide variety in these devices, with some being able to filter more than others, if you live in an area with a lot of air pollution, anything is probably better than nothing.

Water quality
Though the municipal water supply is very safe, depending on the region and your local plumbing, there are several possible contaminants that can potentially affect your health. It would be difficult to cover an exhaustive list, but lead and per- and polyfluoroalkyl substances (PFAS, or “forever chemicals”) are two good examples. Lead exposure is associated with an increased risk of dementia,²⁴ and though exposure has decreased with the banning of lead in gasoline, there are still millions of lead pipes that supply water in certain areas of the United States.²⁵

The risk from PFAS has only been appreciated more recently, but early evidence suggests you can commonly find them in food packaging, nonstick cookware (especially if old or damaged), and drinking water. These forever chemicals can accumulate in the brain, potentially increasing your risk of metabolic disease and dementia.^26,27 As with air filters, there are many different options for water filters on the market, but even the basic versions can remove the majority of heavy metals and PFAS in the water, which can add up to a lot of benefit over time.

Microplastics
These tiny particles shed from plastic containers, tubes, and pipes and can end up in what we eat and drink. One recent study that took social media by storm suggested that we consume, on average, a credit card’s worth of microplastics per week.²⁸ However, another group reanalyzed the data and suggested the true amount might be less than 0.0001% of that.²⁹ Several studies have also supposedly found microplastics throughout the body, including in blood vessels and the brain.³⁰ One study even suggested that microplastic levels were much higher in the brains of people who had dementia than those who didn’t.³¹ However, we don’t yet know if microplastics play a role in the development of dementia. For instance, vascular disease is seen in most cases of dementia, resulting in slow or inadequate blood flow to the brain. This probably makes it more likely that any microplastics in the blood will eventually lodge themselves in the brain. So microplastic accumulation in the brain may well be a consequence, rather than a cause, of dementia.

We also don’t know if these studies are even measuring microplastics in the first place. To measure microplastics in the brain, tissue samples are heated up to high temperatures through a process called pyrolysis. A mass spectrometer is then used to measure the amount and type of plastic compounds such as polyethylene. The problem is that polyethylene is just a simple string of carbons and hydrogens. Fats are also a simple string of carbons and hydrogens and can look like polyethylene once heated up through pyrolysis. As a result, there’s debate as to whether pyrolysis is a valid method for looking at microplastics in the body, where high amounts of fat will always be present.^32,33

With that said, even if the estimates of microplastic exposure and accumulation in the body are exaggerated, this is not a problem we should ignore. Many components of plastics, such as bisphenols and phthalates, have been linked to neurodevelopmental disorders in children and heart disease in adults.^34,35 We can dramatically reduce exposure to (micro)plastics by drinking (filtered) tap water instead of plastic bottled water, using wooden or metal cooking and eating utensils, storing and microwaving food in glass containers, and increasing intake of fresh foods that have not been stored in plastic. While many microplastics are probably eliminated by the body naturally, one very interesting study suggested that anthocyanins from fruits and vegetables might help counteract some of the negative effects of plastics on health.³⁶ Another study in mice found that β-glucan—a fiber found in oats and mushrooms—might decrease absorption of PFAS.^37,38 Though this work was done in animal and test-tube studies, and there are currently no trials in humans yet, the recommendation is simply to eat more fiber and berries. This can also provide other brain benefits because there are a vast number of human studies showing that berry intake can improve cognitive function in both the short and long term.³⁹

Set-and-forget strategies to reduce environmental exposures

For air filters, the blood pressure study I mention used the HealthMate. Jaspr units come highly recommended, as do most of the Blueair models (tailored to the size of the room). The Coway Airmega is a good budget option. Consider checking your local water quality online (EPA, EWG) and then start using a water filter if needed. This could be either a jug that you can place in the fridge (e.g., all-rounders like Epic, ClearlyFiltered, and Brita Elite or Cyclopure, specifically for PFAS) or under-sink reverse osmosis devices that filter water on its way to the tap. 

Oral Health as Brain Health

If you haven’t seen your dentist for a while, now might be a good time. Don’t get me wrong: the irony of a Brit writing about the importance of dental health is not lost on me. But there is an ever-increasing amount of research suggesting that oral health can directly impact brain health. Periodontal disease, as it is more formally known, can start as inflammation of the gums (gingivitis) that can eventually affect the underlying ligaments and bone (periodontitis). Periodontal disease is caused by an imbalance of the microbiome in the mouth, which leads to the overgrowth of certain bacterial species like Porphyromonas gingivalis and Streptococcus mutans. This imbalance of bacteria can cause tooth decay and local inflammation that provides a route for bacteria in the mouth to enter the body. 

More than twenty years ago, P. gingivalis was found in arterial atherosclerotic plaques known to cause heart attacks and strokes.⁴⁰ And since then, researchers have collected reasonably strong evidence to suggest that poor oral health plays a direct role in the risk of heart disease—either because of bacteria invading the arteries after they enter the bloodstream or through an increase in chronic inflammation.⁴¹ More recently, P. gingivalis has also been found inside amyloid plaques in the brains of individuals with Alzheimer’s disease.⁴² As amyloid can have antimicrobial effects,⁴³ it’s believed that one reason for it to accumulate in the brain is as an immune response to the presence of bacteria and viruses that are causing local inflammation. In line with this, though the results of individual studies are inconsistent, meta-analyses suggest that those who have periodontal disease are at an increased risk of cognitive decline and dementia, while treatment of gum disease is associated with decreased risk.^44-47 

One recent study using data from the NHANES database in the United States found that those with worse oral health were more likely to be diagnosed with Alzheimer’s later in life.⁴⁸ The study also measured the amounts of antibodies against oral bacteria like P. gingivalis. Higher levels of antibodies that fight bacteria from the mouth were associated with an increased risk of Alzheimer’s disease, suggesting that those with an invasion or infection by those bacteria were more likely to experience cognitive decline. Therefore, staying on top of oral hygiene likely has both direct and indirect benefits to brain health, while also being easy to do and low risk.

Strategies to improve oral health

If you don’t already, brush your teeth every day (ideally, at least two minutes twice a day) and find a way to clear out stuff that accumulates between your teeth and near your gums (floss, water flossers, or interdental toothbrushes). See your dentist or dental hygienist at least a couple of times a year and treat any periodontal disease promptly. In the case of periodontitis specifically, you could consider chewing xylitol gums (2–3 grams of xylitol, 2–3 times per day) or using a xylitol mouthwash, such as TheraBreath or ACT. Most xylitol gum studies use Epic, but I like Kaigum as well. 

Cognitive Training That Actually Works

In my book The Stimulated Mind, I make the case that the way we use our brains dictates how they function. The way we respond to cognitive stimuli is then determined by the modifiable factors associated with cognitive function, many of which are mentioned above. Though there is a vast amount of evidence for the benefit of education and stimulating work, hobbies, and activities in terms of better cognitive function and lower dementia risk,⁴⁹ we also have some very recent evidence that cognitive training may contribute as well.

The largest, and probably still the best, study of brain training was the Advanced Cognitive Training for Independent and Vital Elderly (ACTIVE) study. Started nearly 30 years ago, ACTIVE randomized 2,800 participants aged 65 or older to a control group or one of three brain-training groups: processing speed, reasoning, or memory. Memory training involved learning tools like mnemonics to memorize lists of words. Reasoning training involved searching for patterns in sequences of numbers or letters. Processing-speed training involved identifying an object on a computer screen that was flashed up at increasingly brief intervals, as well as having to divide attention between two search tasks. Participants did ten training sessions of around sixty minutes over five to six weeks, followed by brief booster sessions at one year and three years. Five years later, all three training groups had experienced less decline in quality of life compared to the control group, with the largest benefit in the processing speed group.^50-52

The ability to process information within milliseconds is critical to everything from decision-making to memory and performing complex skills like driving or playing a sport. Processing speed tends to decline with age, with one analysis of more than one million people suggesting that a significant decline in processing speed begins at around 60.⁵³ However, I would argue that at least part of this is because we tend to stop doing activities that require us to rapidly process information, because ACTIVE found that processing speed in older adults can be improved through training. Most important for our purposes here, a very recent 20-year follow-up of the ACTIVE study found that those who did processing speed training, including the booster sessions, had a significantly lower risk of dementia compared to the control group.⁵⁴

An updated version of the processing speed task used in ACTIVE—“Double Decision,” in which participants identify a central object while also locating a peripheral target under increasingly brief and demanding conditions—is included in the brain training platform BrainHQ.⁵⁵ BrainHQ offers exercises (free and paid tiers are available) targeting memory, attention, processing speed, people skills, navigation, and related cognitive abilities and was designed by a team of neuroscientists led by Dr. Michael Merzenich, co-inventor of the multi-channel cochlear implant. Another study using Double Decision found that processing speed training improved certain aspects of acetylcholine signaling in the anterior cingulate cortex, which plays a critical role in attention, decision-making, and impulse control.⁵⁶ This may be one way that processing speed training translated to improved cognitive outcomes in ACTIVE.

Though ACTIVE gives us some good evidence for the potential benefit of a specific type of dedicated cognitive training, it’s likely that similar benefits can be found in a range of activities that stimulate our ability to rapidly process information. For example, playing musical instruments, dancing, and sports with a coordinative component have all been linked with improvements in brain structure and function, as well as a lower dementia risk.⁴⁹ One of my favorite recent studies, called “Creative Experiences and Brain Clocks,” looked at the influence of creative arts such as dance, visual art (drawing, painting), and music on the brain.⁵⁷ They found that those with greater expertise in one of these skills had younger-looking brains based on improved connectivity in networks that are susceptible to the aging process. The most important network was the fronto-parietal network, involved in attention and decision-making. This suggests that learning and gaining expertise in complex skills can help to maintain brain functions that otherwise tend to decline with time.

One final activity that overlaps with both creative skills and brain training is video games, which can require navigating a large and complex world and solving problems, quickly reacting to the environment, and careful strategic planning. The creative arts study included a randomized trial where participants were trained to play StarCraft II, which resulted in benefits to brain networks that paralleled those seen with creative skills. This is just the latest in a long string of evidence that playing video games—especially in those who were previously non-gamers—can promote certain aspects of cognitive function. 

In one classic study, researchers had adults aged sixty to eighty play solitaire, Angry Birds, or Super Mario 3D World for thirty minutes every day for four weeks.⁵⁸ At the end of the intervention, adults in the Super Mario group showed better improvements in a test of hippocampus function, which was similar to results they had previously seen in undergraduate students.⁵⁹ Other groups have shown that playing Super Mario increases the gray matter in the hippocampus of older adults and can improve feelings of well-being and working memory in individuals with depression.^60,61 Importantly, Super Mario doesn’t have a monopoly on cognitive training, and it’s probably the complex immersive nature of the game that is most important, because other games, like Minecraft and various action video games, have been found to be beneficial in a similar way.^62,63

Strategies to stimulate and train your brain

Dancing, martial arts, music, brain training, video games, etc.—it probably matters less what you pick, so choose a creative art, physical activity, or complex skill that requires focused attention and rapid information processing. The goal is to progressively challenge your cognitive muscles and then maintain practice to keep those skills and networks sharp.

Protect What You Have: Hearing, Vision, and Illness Prevention

If cognitive stimulus is a primary driver of cognitive function, it makes sense that we should do whatever we can to avoid the loss of that stimulus. For example, multiple studies have found that people who lose their hearing or eyesight with age tend to be at an increased risk of dementia—especially those who are at higher risk due to other reasons, such as chronic medical conditions.^64-67 Not only does sensory loss result in a loss of inputs to the brain, but people who lose a sense are also less likely to engage with the world in ways that they used to. As a result, they may be more likely to stay at home and perform fewer activities, decreasing stimulus indirectly. Both hearing and vision loss were included on the Lancet Commission’s list of modifiable risk factors, and this risk does appear to be reversible—for instance, if somebody gets hearing aids for hearing loss or surgery if they’re losing their sight due to cataracts.^64-67

A more insidious loss of stimulus and function comes from the accumulation of periods where we’re unable to experience our normal physical and cognitive stimuli. An analysis from the Adult Changes in Thought study—where adults over sixty-five had their cognitive function assessed at regular intervals for several years—found that cognitive decline rapidly accelerated when a participant was hospitalized between assessments. And the more severe the illness, the more severe the decline.⁶⁸ Similar results were seen in the Rush Memory and Aging Project.⁶⁹ Outside of older adults, there are studies that show even just two weeks of forced bed rest in otherwise healthy people can significantly impair cognitive function due to the loss of critical inputs from physical activity and other cognitive stimuli.⁷⁰ And within a few weeks of an extended period of inactivity, processing speed also starts to decline.⁷¹

A fascinating recent study looked at the effect of the shingles vaccine on dementia risk.^72,73 In 2013 the National Health Service in Wales rolled out a shingles vaccine program based on date of birth. If you were born before September 1, 1933, your chance of getting the vaccine was essentially zero percent, but almost 50 percent of the people born between September 2, 1933, and September 1, 1934, got the vaccine. As you might expect, there was a sudden decrease in shingles diagnoses in those eligible for the vaccine. There was also a sudden drop in dementia diagnoses. Part of the benefit came from preventing or minimizing shingles reactivations, but the authors suggested that there might be a broader benefit of the vaccine for inflammation and the immune system. The same team used a similar approach to study data from when the shingles vaccine was implemented in Australia in 2016 and found the same association with lower dementia rates.⁷⁴ Similar studies have also now been done in the US and Canada, with similar results.^75,76

While we wait for more definitive studies, I think current data give us something to apply practically. We know that it’s impossible to completely avoid viral infections, and it could be counterproductive to try. At the same time, as we get older, we are increasingly susceptible to viral infections that have the potential to knock us back for long periods, or worse. If we think about all the accumulated illness we might experience over decades, each time losing a little fitness and a little muscle mass and a little cognitive function, it’s going to add up. As a result, we may end up thinking that we’re just succumbing to the inevitable process of aging, when in fact it’s the accumulated total effect of periods when our bodies weren’t able to receive (and respond to) physical and cognitive inputs. This makes illness and injury prevention a critical part of long-term brain health.

Strategies to keep what you’ve got

Consider hearing aids and visual aids/interventions as soon as you need them, as these have been associated with lower dementia risk. An increasing body of evidence also suggests that it would be prudent to take advantage of vaccinations and early treatments for viral infections like flu and shingles to minimize the time spent out of action, which then also appears to translate to a lower risk of cognitive decline and dementia.^75-79

Sleep: The Missing Factor

Perhaps the clearest omission from the Lancet report was poor sleep as a risk factor for dementia, which is fairly well established at this point.^4-6 However, I’m also pretty sure most people have accepted the idea that sleep is critical for cognitive function and physical health.⁷ 

Therefore, I won’t belabor the usual recommendations:⁸⁰ keep your bedroom cool and dark, get morning light and dim the lights in the evening to anchor your circadian rhythm, take a warm shower/bath before bed, use a sleep mask, consider a magnesium supplement, and spend enough time in bed (obvious, but still the most common problem I see in people not getting enough sleep). Ventilation and air quality can also matter for sleep because CO₂ levels climb quickly in a closed room, particularly when multiple people are sleeping in the same room, and elevated CO₂ degrades deep sleep.^81-83 In addition to these basics, a handful of lesser-known strategies deserve more attention and may be worth considering:

• The practical implementation for those who can’t spend 30 minutes outside in the morning: light boxes or glasses. Use a light therapy box for 20–30 minutes early in the day (aim for one with at least 10,000 lux like a Verilux). If you’re travelling or don’t want a new light fixture, try AYO glasses, which are used by a number of professional athletes who regularly deal with jet lag and have been found to helpi mprove sleep in both submariners and healthy adults.^84,85
• Glycine. 3 grams of the amino acid glycine taken before bed may decrease sleep latency (the time it takes to fall asleep) and improve sleep efficiency (the amount of time spent asleep), primarily by accelerating the decrease in body temperature that facilitates the onset of sleep.^86,87 Glycine is available from Pure Encapsulations and Thorne, but if you take magnesium before bed, then 400 mg of magnesium as bisglycinate will also provide close to 3 grams of glycine. (Note: The 400 mg is just the magnesium; more than 85% of magnesium bisglycinate is glycine, so the glycine attached to the magnesium adds a few grams.)
• Serine. Another amino acid with circadian effects, studies show that 3 grams of L-serine taken 30 minutes before bed can make melatonin rise earlier. This is useful for helping to set a new bed time when dealing with jet lag, and can also prevent a circadian shift caused by social jet lag (e.g., staying up late on weekends).^88,89 Sources include Double Wood and Now Foods.
• Theanine. Two recent systematic reviews found that around 200 mg of L-theanine taken prior to bed may improve sleep, particularly measures of sleep quality.^90,91 L-theanine is available from Thorne, Pure Encapsulations, and Momentous.
• Hemoglobin testing. While you’re getting your homocysteine checked by your doctor, get a CBC and iron panel to check iron status and hemoglobin levels. Anemia (hemoglobin below 12 grams/dL in women or below 13 grams/dL in men) is associated with an increased risk of dementia,⁹² and is often caused by low iron but can also be due to B vitamin deficiencies or chronic inflammatory health conditions. Symptoms like fatigue and changes in cognitive function in perimenopause are also commonly related to low iron.⁹³ On the other hand, if hemoglobin is high (more than 15 grams/dL in women or 17 grams/dL in men), one of the most common causes is obstructive sleep apnea, which has also been linked with higher dementia risk but this can be mitigated with treatments like CPAP.^94-97

***

If the majority of dementia cases truly are preventable, a sensible approach would be to tackle our own individual risk factors and stack the deck in our favor. 

By building on the big lifestyle rocks with these simple and targeted interventions, we can improve multiple aspects of physical health while maximizing our chances of staying sharp for decades to come.

References (Click the arrow to reveal.)

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Tommy’s new book is The Stimulated Mind: Future-Proof Your Brain from Dementia and Stay Sharp at Any Age.

Photo by Milad Fakurian.