Why do we die of old age?

Roberta Torricelli

“Old age” is very difficult term to define. We know that the definition of old age can involve a number of factors, ranging from our numerical age to our psychological age and biology. Biologically speaking, ageing and old age are defined by the deterioration of our functional characteristics, caused by an increased inability of our cells to grow and divide. This phenomenon is known as cellular senescence. As cells become senescent, they become less good at performing their functions; for example, cardiomyocytes, the cells that make up the muscle of our heart, become less efficient at pumping blood, while our neurons become slower and less prone to wire together to form new memories. This is true for all cells in our body, although some systems might be affected sooner or apparently more than others. As we age, for the same reason, we also struggle to get rid of waste products. These substances can therefore build-up in our body and interfere with normal cellular processes. Aging and “dying of old age”, are therefore characterised and explained by a progressive loss of tissue and organ function. However, it doesn’t end here, it’s not that simple.

Although cellular senescence is recognized to be part of the “normal”, natural cycle of a cell, we are still unsure about which factors can contribute to it. Understanding which factors are involved might explain why not everyone ages the same way, why certain elderly people look younger and feel younger than others the same age.

Some scientists believe that these differences could be attributed to changes in oxidative stress in our body. Oxidative stress occurs when there is an imbalance between free radicals, very reactive molecules that have an uneven number of electrons, and antioxidants, which act as neutralising molecules. To this date we have a lot of evidence in favour of this hypothesis; oxidative stress is in fact involved in several age-related conditions including cardiovascular diseases, chronic obstructive pulmonary disease, chronic kidney disease and neurodegenerative diseases. Both sarcopenia (loss of muscle tissue) and frailty (decreased physical resilience) are two phenomena often seen to accompany old age which have also been observed to involve oxidative damage.

But if we know that oxidative stress (free radicals) is what causes ageing or age-related death, can we stop it and prevent our bodies from ageing or dying of old age? Once again, the answer isn’t that simple. We can prevent some of the damage that oxidative stress does by maintaining a healthy diet, rich in antioxidants found in fruits and vegetables, and avoiding foods which can result in the production of free radicals, such as sugary snacks and meals with lots of unsaturated fats. Incorporating a healthy lifestyle is also a helpful solution; for example, by exercising more and wearing sunscreen when exposing ourselves to UV light from the sun we avoid causing further oxidative damage. Quitting smoking, another major source of free radicals, is another important lifestyle change.

These factors, such as diet, exercise and good living habits, might be the reason why some people (and even some populations!) seem to age better, or slower, than others.

However, senescence isn’t necessarily a bad process; effectively, it protects our body from the damage that older, “faulty” cells could do if not removed.

For these reasons, dying of old age is inevitable but we can potentially live longer, or at least healthier, if we try to follow better lifestyle decisions.