Neuroscientist: If You Don’t Have These 3 Things After 40, Your Brain Is at Risk For Dementia

1. RCDr. Rangan Chatterjee0:00

   You state that 45 to 70% of dementia cases may be preventable. You also state that when you say that to people, there's often disbelief-

2. TWDr. Tommy Wood0:11

   Mm-hmm

3. RCDr. Rangan Chatterjee0:13

   ... and/or resistance.

4. TWDr. Tommy Wood0:14

   Yeah.

5. RCDr. Rangan Chatterjee0:16

   Where does that statistic come from, and why do you think so many people push back at it?

6. TWDr. Tommy Wood0:22

   That statistic comes from two separate studies. 45% comes from The Lancet, uh, Commission on Dementia Prevention report. There have been two now. The first was in 2020. Uh, most recent one was in 2024. They upgraded the, uh, the number from 40% of dementias potentially being preventable to 45%. The 70% number comes from a study using UK Biobank data performed by Professor Ying Kai Yu's group. Um, and they sort of looked at all the different modifiable, uh, factors and risk factors for dementia to estimate, you know, if we removed all of these risk factors from the population, what proportion of dementias would we expect to, you know, n- no longer happen? And this is what, essentially what The Lancet Commission report does as well. So they have these statistical ways of estimating how much a given risk factor translates to a proportion of dementia in the population. It is an artificial way of doing it because we know that risk factors to any chronic disease are not a one-to-one thing, right? And people often have multiple risk factors together and they compound and they interact. But that's the, the best way to, to truly estimate right now how, um, different aspects of the environment and society impacts dementia risk. And so it's things like 7% of dementias are thought to be preventable if everybody got access to high quality education, um, and, you know, high levels of educational attainment. And then there are, um, uh, risk factors related to smoking, head trauma, obesity, um, hearing loss, et cetera. And the, the 45% number from The Lancet, uh, Commission report, I think that could be conservative because they didn't include things like poor sleep, which we know is a risk factor. They didn't include things like, um, late, uh, later life cognitive stimulation, which we know is important as well. So that's why potentially this, you know, 70% could be the, the upper limit perh- perhaps, um, of dementias that are preventable. But you're right that when you say something like that, first of all, people are surprised. I think this is, this is new information. Um, and then people, especially those who have some kind of relationship with dementia, they have a loved one or family member with dementia, they have a family history of dementia. 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, right? We've just said that we're only just starting to appreciate that dementia may be preventable or, you know, a certain proportion of dementias may be prev- preventable, certain types of dementia may be preventable. And we know it's very complicated, right? Multiple risk factors may come together in an individual, uh, genetic risk factors, environmental risk factors. Um, and I truly believe that each person is doing the best with the information that they have and the things that they can do at the time. So it's more an idea of hope, right? Should we be able to modify our environment? Should we be a- be able to make societal change to remove some of these risk factors? 'Cause some of them are related to socioeconomic factors. There is, um, the possibility of dramatically de- decreasing dementia burden in the population. And yes, individually we can take that on and, and, uh, decrease our own risk of dementia. But it's, it's really, um, sort of an idea of, of what's possible rather than saying, "Oh, because somebody, uh, got dementia, they did something wrong."

7. RCDr. Rangan Chatterjee4:07

   Yeah. It's... It-- That whole thing about blame is something I think a lot about on this show 'cause each week we're trying to empower people with the things that you might be able to do in your own life. It doesn't mean though that if you get something, you failed in some way.

8. TWDr. Tommy Wood4:25

   Yeah. Yeah.

9. RCDr. Rangan Chatterjee4:25

   Do you know what I mean?

10. TWDr. Tommy Wood4:25

    Yeah.

11. RCDr. Rangan Chatterjee4:26

    It's, it's a tricky one, isn't it?

12. TWDr. Tommy Wood4:27

    It's also hard for us to, to think about this as individuals because we're talking about probabilities, right?

13. RCDr. Rangan Chatterjee4:35

    Yeah.

14. TWDr. Tommy Wood4:36

    So it would be impossible to say that any individual case of dementia is preventable. It would be very possible to say, were you to address certain risk factors, you will decrease your risk of getting dementia. But I could never say I can guarantee that one individual won't experience dementia. They may experience it later. They may have, you know, less of a decline, fewer symptoms. They may not experience it at all. But it's sometimes hard to wrap our head around the fact that when you're talking about statistics, you're talking about probabilities rather than certainties, and often in the health sphere we're sold certainties and black-and-white stories, and it can be difficult to understand that there's some nuance in, in what we're trying to, to get across and what we could potentially do.

15. RCDr. Rangan Chatterjee5:19

    I think those statistics, firstly, they're very empowering, but I think they're empowering on a couple of different levels. I think firstly it means, "Oh wow, just 'cause Mom had it-

16. TWDr. Tommy Wood5:30

    Mm.

17. RCDr. Rangan Chatterjee5:31

    "... maybe it doesn't mean that that's my fate."

18. TWDr. Tommy Wood5:34

    Yeah.

19. RCDr. Rangan Chatterjee5:35

    And so, "Oh, let me learn more to see what I can introduce into my life." So I think it's hopeful on that level, but I think deeper to that, it, it more broadly to me speaks to our collective attitudes towards aging.

20. TWDr. Tommy Wood5:52

    Yeah.

21. RCDr. Rangan Chatterjee5:53

    Right? Are we expecting our brains to get slower, weaker, poorer, whatever that might be, as we get older?

22. TWDr. Tommy Wood6:02

    Yeah.

23. RCDr. Rangan Chatterjee6:02

    Or do we actually think that that doesn't necessarily have to be the narrative? And, you know, in the new book, The Stimulated Mind, you very clearly make the case that that does not need to be the case. Let's talk a little bit about mindset-

24. TWDr. Tommy Wood6:13

    Mm

25. RCDr. Rangan Chatterjee6:13

    ... and attitude to aging, 'cause I th- I think that's quite key, isn't it?

26. TWDr. Tommy Wood6:17

    Yeah, I, I think so.And this is something that we've embodied as a society almost, that we expect a certain amount of decline as we get older. And I, uh, I lay some of this blame at the feet of Sir William Osler. If anybody's heard of him, he's a, a very famous physician. Um, he's a... Was a Canadian physician, helped to found Johns Hopkins Hospital in the US and then he was a professor of medicine at the University of Oxford. And in the early 20th century, 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, to retire. But he gave this famous address at Johns Hopkins where he said that at the age of 60, the, uh, average adult is useless and should be put out to pasture. [laughs] And this then is something that we have internalized as a society, and this is essentially what we expect. I will give him a little grace by saying that at that time, average life expectancy in the US was in, you know, late 50s. So maybe he was right that once you were 60, you know, the average individual wasn't in great health.

27. RCDr. Rangan Chatterjee7:32

    Mm-hmm.

28. TWDr. Tommy Wood7:33

    But that's no longer the case, right? With the advancement of, of medicine and ev- everything we've been able to do to extend both lifespan and healthspan at the population level. And despite that, I think we expect some level of decline, and because of that, we do things or stop doing things that then make that inevitable. So, uh, there's this, uh, idea of stereotype embodiment theory, um, based on, uh, some of the work, including like Ellen Langer's-

29. RCDr. Rangan Chatterjee8:07

    Yeah

30. TWDr. Tommy Wood8:08

    ... work. You know, you know her work well.

Episode duration: 1:27:10