Use it or lose it: how to sharpen your brain as you age
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Do you like to hunker down with a brain-straining cryptic crossword to scale the intellectual heights of a highbrow novel or plough through Sudokus to keep your faculties sharp?

These are all things we do in the hope of slowing what we perceive as the inevitable decline in our cognitive abilities as we get older. But a new study into human brain power suggests that the decline we've come to expect in later life isn't necessarily a given. The real big takeaway here is that there's no natural law whatsoever that would dictate skill decline with age.

So how does this new evidence challenge the previous consensus? Why is cognitive decline a big issue for ageing populations? And what can we do to stay sharp for as long as possible? I'm The Guardian's science editor, Ian Sample, and this is Science Weekly.

Right. I'm Ludger Wülsmann. I'm an economics professor at the University of Munich, and I'm the director of the IFO Center for the Economics of Education. So, Ludger, you've done some work which challenges some of our previously held ideas about how cognitive skills change with age. But first of all, what has the consensus been up until now?

I think the consensus so far was that cognitive skills pretty much start declining by age 30, if not earlier. And that comes from research where you just look at people at different ages at a given point in time. And you basically see that people who are 40 don't do as well on numeracy and literacy tests than people age 30. And people who are 50 don't do as well as people age 40. So it looks like

all decline as soon as you turn 30. Okay, so that's the evidence from just testing a whole cross-section of people of different ages. And that suggests that cognitive skills start declining from the age of 30 onwards. Although in my case, I've absolutely been in decline since about 14 years old.

Now, before we get to your own work on this, you're an economist rather than a neuroscientist. Why are you interested in this?

So the point is that these type of cognitive skills, math skills, reading skills, also science skills really, have been shown to be super important for economic prosperity, both of individuals, but also in terms of the long run economic growth of entire economies. And then if this pattern of decline is really the true effect of age, this is really concerning because

for societies with rapidly aging populations, as many industrialized economies have right now. So many countries, people on average get older and older. If that means that the skill level of the population, particularly of the working age population, declines over time because of that, we should be concerned about the overall prosperity of all countries. Right, because of course many of us are going to be working into our late 60s and beyond. Right.

So tell me what you set out to study and how your research is different to what's gone on before. So the problem with existing studies is that you, at a given point in time, you compare how people who are aged 50 do compared to people who are aged 40, for example. But the problem is that these are different cohorts and people who are aged 50 may just have had different experiences in terms of schooling, but also in terms of overall deprivations, what have you.

And so you never know whether the people who are 50 today are like a good counterfactual for what people who are 40 today would look like in 10 years time.

Now, the really cool thing is that there's a major data collection scheme called PIAC. That's the Program for the International Assessment of Adult Competencies that actually in many, many countries has given numeracy and literacy tests to representative samples of the adult population. So that's like this one cross-section that we have. But then the even better part is that

Germany is actually pretty unique among these participants that they actually went back to the original people who took the test. And then between three and four years later, had the same people take the test again. And so now we actually can look at within individuals on how their skills has literally changed over time. So we're not comparing different people at one point in time. We look at how do your skills when you're 30 look like if you are 34.

And the interesting thing is that gives us a totally different picture from the cross-section. You were also able to measure in these data how...

how frequently people were using particular skills though. So where did those data come from? Right. The other thing is that this PIAC data set, they ask people about lots of things that they're doing both at work and at home. And so they have lots of items that ask like, how often do you read directions or instructions? How often do you read letters or emails?

newspapers, and so on and so forth. And then actually on the math side, they ask you how often do you have to calculate prices, use fractions, use a calculator, or prepare charts or tables. And so from these, we basically construct an index of how often different people use math skills and how often they use reading skills at home and at work. You pulled all these data together then, Lugger. What did your analysis show?

So there's really two main results that we find. So first of all, the average skills actually increase strongly into the 40s. So really, if you look at how people do over time, even into the 40s, people keep increasing their skills. And then after that, we see slightly decreasing skills in literacy and more strongly decreasing skills in numeracy, even though even in numeracy, it doesn't go below levels

that you are at, say, in your mid-20s. So that's the first part of the results. And then the second part relates to these skill usage methods that you just referred to. So what we basically see is the huge differences in how your skills change over time depending on

or whether you use skills often or not. And the high users, for them, skills literally never decline, even until age 65, until which we can observe them. And only among the relatively low users, we actually see decline that starts much earlier and is stronger. Okay, so the average person's cognitive skills actually start to decline at least 10 years later than previously thought. So in their 40s rather than their 30s.

But also for people who regularly use their maths and literacy skills, they can stay just as sharp until at least 65. But Luka, who is experiencing decline and who seems to be most protected from that? I mean, these people are clearly doing different things at work and at home, right? That's right. And we see these patterns like quite often.

Similarly, for whether we look at usage at home and usage at work. And so we see on average that white-collar workers are more likely to use both reading and math skills than blue-collar workers. And so for these groups, you see the expected patterns. But even more importantly, even within these groups, among white-collar workers, there are some people who

who use these skills often and some who don't, and the same among blue-collar workers. And we see that even within these groups, that makes a huge difference. So if you're a blue-collar worker, but still you're using skills relatively often, they actually are not going to decline even until age 65. If you're a white-collar worker and use skills very often, they literally keep increasing into the 60s.

Now, you found these differences you've just described between the sort of the regular users and the less regular users, if I can put it that way. But you also saw quite a difference between males and females. Can you take me through that finding? Yeah, that's kind of interesting as well. So in reading, you don't see...

literally any differences in skill usage between men and women, but there's a real difference in numeracy, and that's quite surprising. So we actually do see that men are more likely to use numeracy skills than women are, but that actually can only explain some of the difference in how their skills actually change over their lives.

where we see that actually male skills do not decline even at medium ages, whereas women's numeracy skills decline much more strongly and at earlier ages. So big question is, what explains these results? And it seems that they certainly challenge this idea that cognitive decline is something that we all have ahead of us. Well, yeah. So

I think the real big takeaway here is that there's no natural law whatsoever that would dictate skill decline with age. What we see is actually, on average, skills actually increase into the 40s. And then after that, it really depends strongly on whether you use your skills, so you constantly challenge what you are doing, or if you don't. And so...

If you don't use it, you lose it. And that's, I guess, the main takeaway. Now, the specifics of the numeracy pattern among females actually does remain a bit of a puzzle to us ourselves. It may just be that actually the jobs that women are more likely to have than men are kind of less challenging in the terms of the type of users that you have, particularly among numeracy skills.

I wondered whether some of that sex difference might have been driven by kind of historical inequalities where we know in the past that women haven't had the same access to education. They haven't had the same job opportunities of men. I don't know if this is a hangover of that.

So, like, if you look at engineering, you still see a huge over-representation of male people going into these majors and going into these occupations. And if these are the types of occupations that challenge your skills, like, much more often, even at higher ages, then that could actually explain part of this gender pattern indeed. ♪

Standing back from this, Lugger, your research shows that these falls in numeracy and literacy aren't necessarily inevitable as we age, but the declines are there. And

perhaps they're then even worse than the averages suggest in some people, such as the blue-collar workers who aren't using these skills very much. So it seems like there's kind of some good news from your study, but also some pretty worrying news. Yeah, it's basically two sides of the same coin. Basically, what the data show is use it or lose it. And so that really means we should

practice our reading skills and same about both math type of skills. And as long as we're doing that, we probably don't have to be afraid that our brain power will decline at least until the age 65 that we can observe in our data. So it's, I think it's just a

Just important to realize we shouldn't slack off. Finally, Ludger, I know you're not in your advanced years by any means yet, but is there anything you do to prevent cognitive decline yet? Or does your job and sort of lifestyle already have that covered? Mm-hmm.

Well, I guess the job hopefully does so, at least doing these type of analysis is quite challenging, to be honest. But even playing games, reading things are types of things that actually will make sure that we shouldn't be too much concerned about cognitive aging after all. Brilliant. Ludger, thanks for coming on. Thank you so much. Thanks again to Ludger Wurzmann.

And that's all from us today. This episode was produced by Ilan Goodman. It was sound designed by Tony Onuchuku and the executive producer was Ellie Burey. We'll be back on Tuesday. See you then. Hello, I'm Jonathan Friedland from the Politics Weekly America podcast. Donald Trump has started his second term. It's going to be a turbulent period and The Guardian will be here covering it all.

This is The Guardian.

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