A question of mind over matter?

It is the billionaire club’s pet project — slowing down or even reversing the ageing process in humans. And it is no secret how big a business anti-ageing has become. But how does our brain alter as we grow older?
Last Updated : 12 December 2021, 02:37 IST

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One of the nicest things about childhood is the feeling that we’ll never get older. Next comes the decade or two of wanting to be older than we are and yearning to be taken more seriously. Then suddenly, we’re on the other side of the spectrum, looking on wistfully at younger people. George Bernard Shaw famously said “youth is wasted on the young”, and I’m quite sure he was a wistful not-so-young person when he said those words.

Growing older is one of those things we don't have time to think about when we are young, but which catches up with us before we realise it. We all come to understand, at some point in our childhoods, that ageing and death are an inevitable part of life. While immortality might not be on the horizon, scientists have been finding out more and more about why we age, and what we can possibly do to increase the number of healthy years that we have in our lives.

When people in the prime of their youth think about old age, they think primarily in terms of a decline — in mental acuity, physical strength, and the senses. While all these tend to happen as we age (for reasons that we shall explore in a bit), it is not a downward graph on all faculties. For instance, older adults might be slower at information processing, but they generally tend to be better at finding patterns and seeing the bigger picture. This is probably a welcome side-effect of older adults having had many more experiences in life (and thus many more opportunities for generalising information). It also goes without saying that an older adult is probably several fold more resilient than a younger person. The calamities of youth appear as mere speed-breakers to an older adult — nothing that they haven't faced and recovered from!

All this is not to paint a rosy picture of old age. The issues that so many older adults face, be it sensory decline or memory loss, are real and can be disabling and even de-humanising.

We all know that 90-year old who doesn’t seem a day older than 60, and at least a few 60-year olds who seem much older than they are. How well or how poorly we age depends on a complex cocktail of factors from our genes to stressors in our environment, to, of course, sheer dumb luck.

Why do we age?

Several theories have been put forth by scientists to explain why we age at a cellular level. Some hypothesise that we age because of an accumulation of genetic damage with time, while others propose that it is changes in hormones that are responsible. There are also theories that suggest that older adults are more vulnerable to disease because their immune systems decline with time. David Sinclair, Professor of Genetics at Harvard, has propounded the Information theory of ageing. Before we get into the details of this theory, however, we need to learn a little bit about genes and their expression.

All the cells in our body have an identical set of genes. What makes a heart cell different from a nerve cell is simply that different genes are switched on or off in each cell. It is the wrapping of our genetic material around proteins that decides which genes are turned on, and which are not. If the genetic material, or DNA, is wound tightly around a protein, then the messages in the genes in that region of our DNA cannot be read and transformed into information, so the gene is said to be turned off. According to Sinclair's theory, it is not direct damage to our genes, but changes in mechanisms that support optimal expression of genes in our cells that are responsible for ageing.

In one of his popular talks on YouTube, Sinclair gives the example of information on a CD — if the CD is scratched, the CD player cannot properly read the information in the CD unless the scratches are wiped away somehow. Ageing through these "epigenetic" mechanisms — how our behaviour and environment control the expression of our genes — works in a similar way, he says. Our DNA and the genes in it might be intact, but if the gene expression is messed up somehow, then our cells lose their identities because the wrong genes are turned on or off. This could be one of the causes for age-related decline.

What happens to different faculties as we age?

* Memory: All is not bad news

Just last week, I spent five minutes searching for my glasses that were perched snugly on the top of my head. I had put them there myself just a few minutes prior, but I had absolutely no memory of doing so whatsoever, and also, quite embarrassingly, didn't notice the sensation of my glasses on my head the entire time that I was searching for them! Now since I am only a couple of years into my thirties, I shrugged off this episode as mildly embarrassing, more than a little funny, and told myself I must have been tired that particular day. I can imagine the same thing happening to a 70-year old, and they would have immediately been convinced it was an early sign of dementia. This is not to say that dementia is not a serious disorder that affects a sizable portion of older adults, but to make the point that not all memory lapses are abnormal or a sign of something sinister to come. Disorders such as Alzheimer's are not an inevitable or an expected part of ageing, and affect fewer than 1 in 5 people aged 65 and older.

Some memory decline, however, is expected as people age. Episodic memory, which is the memory of everyday events in our personal lives, typically tends to decline with age. This happens because the hippocampus, a region in the brain that is responsible for the encoding and retrieval of episodic memory, tends to shrink as we get older. This is why older adults often report going to a different room in the house and forgetting why they went there in the first place, or forgetting where they parked their car or left their keys.

Another thing that seems to happen with age is that we tend to forget what words sound like. This "phonological" memory is sub-served by a structure in the brain called the insula, which also seems to atrophy with age. This is why our grandparents often tell us that they had a word "on the tip of their tongue". They don't forget the word itself — they would recognise the word and understand its meaning if they read it an a sentence — they just forget what sounds to use to form the word.

There is also a general slowing down that occurs in the brain of older adults, thanks to a process that causes decay of a structure called the myelin sheath that helps neurons communicate faster and more effectively. Some dietary additions that help with myelin formation and maintenance are omega-3 fatty acids and Vitamin B12.

So the brain gets slower in general, and some kinds of memory are impaired with age — but all is not bad news. Our memory for motor skills that we learnt when we were younger remains largely intact as we age. Research suggests that along with learning a manual skill or two when we are younger and keeping it up as we get older, picking up a new skill in old age can be protective against memory decline. Of course, this can be frustrating for older adults because the brain finds it harder to pick up new motor skills as we age. But with a greater degree of concentration and more time, these new skills can be picked up even by a 90-year-old.

All this is not to suggest that an optimistic outlook and a new skill or two are all it takes to fend off memory decline, or that it is even possible to do so for everyone under all conditions. Like I'd mentioned earlier, our genes play a role, as do factors like stress. Scientists also suggest that people with a higher level of education and intelligence may be able to better cope with ageing related changes in the brain because they have a higher "cognitive reserve". Cognitive reserve, in addition to a high level of education, also depends on occupational complexity. The more intellectually complex the work we do is, the more likely we are to have to keep learning and sustaining mental effort and engagement.

* Personality: The la dolce vita effect

Try to think of yourself as a teenager. How different is your personality now than it was then? We are all changing all the time, and age and life experience cause us to experience life differently and react differently to new situations. Scientists describe five broad aspects of personality — extraversion, agreeableness, openness, conscientiousness and neuroticism — with each having sub-categories of their own. Older adults seem to show a decline in extraversion and openness but score higher on traits like agreeableness and emotional stability. Oh and of course, there's also the la dolce vita effect, which is Italian for "the sweet life". Older adults generally score higher on life satisfaction. In fact, if you ask people who've lived a long life when they were happiest, the number that usually tends to come up is 82!

What is interesting about these various domains of personality is that they are not set in stone. In studies on people with Type 2 diabetes, for instance, patients reported that they started taking more care of their health after getting the diagnosis for the disease. It could be that simply deciding to lead a healthier lifestyle might change people's personality for the better, leading to increases in scores on traits like self-control and conscientiousness.

Starting something new later in life, be it a new skill or a new business venture, might also work in a similar way to promote longevity. When we are curious and engaged, it leads to better health outcomes in general. It has also been shown that people who score high on curiosity are more likely to challenge themselves and thus benefit from the intellectual engagement that results in.

* Intelligence: Crystal versus fluid

Like memory and personality, intelligence has many domains as well. For instance, fluid intelligence is the kind that helps us learn new things — it involves faculties like reasoning and problem-solving. Crystallised intelligence, on the other hand, helps us recall knowledge and experiences that we have stored in the past. We need both these to work together to accomplish many of the tasks we do in our day-to-day lives. Scores on tests measuring fluid intelligence tend to decrease with advancing age — this is why, for instance, older adults are often stumped by a new piece of technology.

Another kind of intelligence, practical intelligence, which measures how well a person applies their knowledge in the real world, seems to get better with age. This is one of the many reasons why older adults are seen as valuable contributing members in many countries that do not have a mandatory retirement age. Neuroscientist Daniel Levitin, in his book Successful Aging, writes a lot about the cognitive and emotional decline that seems to accompany retirement for many older adults. "Old age often brings retirement and (hopefully) the independence of our children, and with that comes an important psychological change: We are no longer responsible for performing a particular function within an organisation or in society. That loss of a sense of responsibility can lead to a more global loss of a sense of agency — a sense that what we do in the world matters, and that we matter to other people."

Many people might enjoy the slowing down that retirement brings to their lives, while others might not take it as well. What seems to be most important is that older adults have a sense of purpose, be it continuing to contribute in some way to society, spending time with their grandchildren, or even indulging their urge to travel and see the world.

At the end of the day, though — no pun intended — how full our lives are depends on factors that are usually way beyond our control. All we can possibly do, to paraphrase a character from the TV series This is Us, is to take the lemons we are given, and try to make something resembling lemonade.

How to age better

* Chronic sleep deprivation and inconsistent sleep-wake cycles have been shown to cause inflammation, age-related cellular damage and oxidative stress. Maintaining a good sleep schedule thus becomes important as we grow older to promote health and longevity.

* When it comes to our diet, much has been said and written about antioxidants and their beneficial effects on health, but the studies all taken together show only a modest effect, if any. What seems to be most beneficial, though, is simply to eat less.

* Caloric restriction has been shown to promote longevity and reduce the negative effects of ageing. Caloric restriction seems to work by turning on longevity genes. Dr David Sinclair of Harvard says we need adversity to become resilient and fight disease, and hunger gives us that.

The author is a neuroscience PhD turned science writer who is fascinated by the workings of the brain and how we can ‘rewire’ it to our advantage.

The Mind’s Eye is a bi-monthly column that explores neuroscience in everyday life.

Published 11 December 2021, 20:01 IST

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