Ageing is inevitable. Or is it? Law Wing Sze, a third-year medical student and the grand winner of the FameLab Hong Kong final, explains the latest research into why we grow old.
Since the beginning of human history, we have been trying to find ways to stay young. Yet ageing is inevitable, and there seems no way to reverse the process. Each of us is born with an internal biological clock, figuratively speaking, that determines our life span. If we knew how the clock worked, we could understand more about how we age, and eventually, we might find the secret to the mythical fountain of youth.
Why do we age?
The human body is made up of cells. Each cell is like a Lego block, and builds various organs for different functions. Cells divide to produce new cells for the growth and repair of body tissues. But cell division is not limitless: on average, human cells can divide only about 50 to 70 times. Afterwards, cells will enter a senescence phase when they no longer divide. At this point, the cells may die, or stay in the body as malfunctioning cells. This causes our bodies to deteriorate and age.
What happens at the cellular level?
To understand the ageing process, we need to look deep inside our cells. Inside each cell, there is a compartment called a nucleus, which contains many strands of chromosomes. Chromosomes contain the genetic materials that control cell division. At both ends, chromosomes are protected by caps of telomeres. Imagine a shoe lace: the telomeres resemble the plastic tips on the ends of the shoelace that prevent it from fraying.
In our cells, telomeres act as buffers to protect the chromosomes from damage. But every time the cell divides, the telomeres are shortened. At birth, we have long telomeres, but as we grow older and our cells continue to divide, our telomeres become shorter and shorter. Each time a telomere gets shorter, the chromosomes are less protected and finally, the chromosomes are exposed to damage, and cell division stops. We age because our cells age.
What accelerates ageing?
As our telomeres get shorter, our 'internal biological clock' ticks. The shortening process is influenced by both genetic and environmental factors. We inherit the DNA that determines the initial length of our telomeres from our parents. But there are also various environmental factors at play. The most prominent of these is psychological stress.
The more stressed you are, the faster you age
In a study published in the Proceedings of the National Academy of Sciences, it was shown that women with the highest levels of perceived stress have shorter telomeres. The study looked at a group of mothers with chronically ill children. It found that the more years they spent caring for their children, the greater the stress they endured, and the shorter their telomeres were.
The scientists further hypothesised that chronic stress increased the level of oxidative stress (damage caused to cells by chemically reactive molecules containing oxygen) in the women's bodies. This sped up the shortening of their telomeres.
Why does chronic stress make you age faster?
Stress is a natural physical response that developed to help our bodies go into ‘fight or flight’ mode when we need to tackle serious challenges. We release a stress hormone, cortisol, which increases heart rate and blood pressure, so we are prepared to respond to danger.
But chronic stress leads to cortisol being repeatedly released, and high levels of cortisol increase cell damage through oxidative stress. Cortisol also counteracts an important telomere-lengthening enzyme called telomerase. So, too much cortisol speeds up the shortening of our protective telomeres, and accelerates ageing.
It's no surprise that people under immense stress age faster than their more relaxed counterparts. If you compare photos of US presidents before and after their tenures in the White House, you will see some clues!
How is diet related to ageing?
Another factor contributing to ageing is diet. In particular, restricting calories is believed to help us live longer. Is this really true? Well, in studies of laboratory animals, calorie restriction has been proved to reduce levels of oxidative stress, improve metabolism, and consequently extend life expectancy. And in recent years, there have also been studies carried out on human subjects. But the mechanism by which eating less might slow ageing is still not clear. One hypothesis is that restricting calories encourages the body to be more thrifty in how it manages cell division, removing damaged components inside cells and recycling their materials first, thereby extending the cells' life span.
Is there any way to slow down ageing?
It may seem that, because we cannot control the shortening of our telomeres, we must all grow old eventually. But although it's true that we cannot escape from ageing, we can slow down the process. A small pilot study by the University of California, San Francisco, showed for the first time that lifestyle changes lead to longer telomeres. Individuals on a vegetarian diet, who took moderate exercise and reduced stress by meeting regularly with a social support group, were found to have longer telomeres. This shows that we can actually do something to lengthen our telomeres and slow down ageing.
How can we reduce stress and therefore slow down ageing?
Psychological stress plays a significant role in ageing. If you live in a big city and have a busy schedule from day to night, it might feel like there's no room to relax. Yet relaxation is of utmost importance if you want to live longer.
One scientific study suggests that meditation may help. Meditation encourages people to focus on the present, and reduces anxiety and distress. By reducing stress, meditation also lowers our levels of cortisol, and thus reduces oxidative stress on our cells. You could also try focused breathing, or exercise, which boosts the release of endorphins that create a sense of relaxation.
Ageing is a natural process that we all go through. But we may slow it down a bit. All we need to do is just improve the health of our telomeres.