Neuroscientist: If You Don’t Have These 3 Things After 40, Your Brain Is at Risk For Dementia
45-70% of dementia cases are preventable through lifestyle modifications, and cognitive function can be maintained or even enhanced at any age. The key isn't accepting decline as inevitable—it's understanding that what we expect often becomes our reality. Challenge your brain with new learning, prio
1h 27mKey Takeaway
45-70% of dementia cases are preventable through lifestyle modifications, and cognitive function can be maintained or even enhanced at any age. The key isn't accepting decline as inevitable—it's understanding that what we expect often becomes our reality. Challenge your brain with new learning, prioritize genuine social connection over social media scrolling, and remember: doing the things that maintain function is what prevents the decline we fear.
Episode Overview
Dr. Tommy Wood discusses the preventability of dementia and the power of mindset in aging. The conversation explores how 45-70% of dementia cases may be preventable through modifiable risk factors including education, sleep, cognitive stimulation, and social connection. Key topics include: • The stereotype embodiment theory—how expecting decline creates a self-fulfilling prophecy • Why most people maintain cognitive function into their 70s and 80s • The hidden dangers of social media on perceived social rank and inflammation • How social isolation changes immune function and increases chronic disease risk • The importance of celebrating what we do rather than worrying about what we don't
Key Insights
Dementia Prevention Is More Possible Than We Think
The Lancet Commission reports that 45% of dementias are potentially preventable through modifying risk factors like education, smoking, hearing loss, and obesity. A UK Biobank study suggests the number could be as high as 70% when including factors like poor sleep and late-life cognitive stimulation. This isn't about blaming individuals who develop dementia—it's about recognizing the hope and possibility for prevention through environmental and lifestyle changes.
Expecting Decline Creates Decline
Stereotype embodiment theory shows that if you expect cognitive or physical decline with age, you embody that belief and stop doing the challenging activities that maintain function—creating a self-fulfilling prophecy. Some South American running tribes believe you get faster with age and their elders remain the fastest runners, demonstrating how mindset shapes physiological reality. Studies show perceived exercise levels affect mortality risk independent of actual activity levels.
Most People Maintain Cognitive Function Into Their 70s and 80s
The Seattle Longitudinal Study by Warner Schaie tracked individuals for decades and found that more than 50% of people maintained cognitive function into their 50s, 60s, 70s, and even 80s. When we see average decline in population studies, it's because some people are 'dragging down the average'—but maintenance of function is actually the norm, not the exception. This data was even used to raise the retirement age in the US.
Social Media Creates Chronic Social Stress
Social media exploits our need for PRIME information (Prestigious, In-group, Moral, and Emotional content). Constant exposure to people seemingly doing more or being more successful than us lowers our perceived social rank, which creates the same physiological stress response as social isolation—including immune system shifts toward inflammation and increased chronic disease risk. The algorithms keep us hooked by feeding information our brain thinks is critical for survival, while actually disconnecting us from genuine social interaction.
Worry Negates the Benefits of Healthy Behaviors
Research shows that people who felt they weren't doing enough exercise compared to others had higher mortality risk, even after adjusting for actual exercise levels and health factors. Similarly, studies on perceived versus actual sleep quality affect next-day performance. When you spend time thinking 'I'm not doing enough,' you create chronic stress that offsets the benefits of what you are doing. Celebrating your positive actions is more beneficial than fixating on perceived shortcomings.
Having Children Reduces Dementia Risk Despite Sleep Disruption
UK Biobank data shows that the more children parents had, the lower their dementia risk—despite the stress, sleep deprivation, and personal sacrifice that comes with parenting. This demonstrates that the benefits of joy, cognitive stimulation, social connection, and pro-social behavior massively outweigh the downsides of imperfect sleep or stress. We need to focus on maximizing benefits rather than worrying about minor negatives.
Social Isolation Changes Your Immune System
When socially isolated or experiencing low perceived social rank, your immune system shifts: it becomes less effective against viruses (since you're not around people to catch them from) and more primed for wound healing (since there's no one to help you if injured). This adaptive response comes with elevated baseline inflammation, which long-term increases risk of heart disease, dementia, and other chronic diseases. This is an evolutionarily conserved physiological response to social stress.
Notable Quotes
"45% comes from the Lancet commission on dementia prevention report. There have been two now. The first was in 2020. Most recent one was in 2024. They upgraded the number from 40% of dementias potentially being preventable to 45%. The 70% number comes from a study using UK bio bank data performed by Professor Yintai's group."
"If you say that dementias are potentially preventable, they might interpret that as if there's some blame on an individual who previously suffered from dementia or is currently suffering from dementia when that's absolutely not the case. We've just said that we're only just starting to appreciate that dementia may be preventable."
"It's more an idea of hope, right? Should we be able to modify our environment? Should we be able to make societal change to remove some of these risk factors because some of them are related to socioeconomic factors? there is the possibility of dramatically decreasing dementia burden in the population."
"Sir William Osler helped to popularize the idea of retirement because before then, other than sort of like military pensions, it wasn't normal for people to retire. But he gave this famous address at Johns Hopkins where he said that at the age of 60, the average adult is useless and should be put out to pasture. And this then is something that we have internalized as a society."
"If you expect decline you then embody this idea that you will decline and therefore you stop doing the things that prevent decline and therefore it becomes a self-fulfilling prophecy. Oh, I'm too old to learn a new language. Oh, I'm too old to pick that up. Oh, you know, I might get injured. I don't want to do that."
"The majority of people so like more than half of people maintained cognitive function into their 50s 60s and 70s. So yes there were some people who lost function. They dragged down the average but the norm you know more than 50% of people was to maintain function over time even into your 70s and 80s."
"When you spend all your time seeing people who are doing more than you, more successful than you, richer than you, better looking than you, whatever, like however you would perceive that compared to yourself. And what we do is then we rank ourselves like where are we in the world? And we demote ourselves internally because we see all these people who we think are better than us or doing more than us."
"If you spend all your time thinking, I'm not doing enough. I should be doing more, you are then essentially creating a situation where you're not getting benefit from the things that you are doing and creating this chronic stressor that's having negative health effects."
"I am much more in favor of celebrating all the amazing things that we do do because those are probably offsetting any of the sort of like the minor things that we would otherwise worry about."
"I think social media takes advantage of our need for social information whilst giving us social disconnection, but we keep going back cuz we're like, well, next time I'll learn something that will really help me."
Action Items
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1
Shift Your Mindset About Aging
Actively challenge the belief that cognitive decline is inevitable with age. Remind yourself that more than 50% of people maintain cognitive function into their 70s and 80s. Start viewing aging as an opportunity for continued growth rather than inevitable decline.
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2
Celebrate What You Do Instead of Worrying About What You Don't
When you engage in healthy behaviors—a 30-minute walk, quality time with loved ones, learning something new—focus on celebrating that action rather than comparing it to what others do or thinking it's not enough. This mindset shift helps you actually receive the benefits of your positive choices.
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3
Curate Your Social Media Use or Take a Break
Remove social media apps from your phone for at least 4 weeks, or strictly limit usage to active connection (messaging friends, sharing with family) rather than passive consumption. When you do use it, be aware of content that triggers feelings of inadequacy or lower perceived social rank, as these create physiological stress responses.
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4
Prioritize Real-World Social Connection
Replace time spent scrolling with in-person social activities. Whether it's having children, volunteering, joining a club, or simply meeting friends for coffee, genuine social connection provides cognitive stimulation, joy, and pro-social behavior that massively outweigh the benefits of online engagement.