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Why Do We Get Old?

Stiff muscles, wrinkles and joint pain. We are all getting older, but how come our bodies show it more and more over time? This turns out to be a difficult question to answer. Ageing is a complex phenomenon involving a wide range of cellular and molecular processes.

In 2022, the average life expectancy at birth in Belgium was 81.7 years. Looking back 150 years, we would have lived to half that age on average. At that time it was rare to meet someone in their 80s. The physical appearance of an older person was quite rare too: grey hair, wrinkled skin, stiff muscles, creaking joints and so on. Now these are all very familiar but we still don’t have a complete answer to the question of why ageing happens.

Greying genes

Damage to our DNA, cells and tissues accumulates as we get older. We don’t yet fully understand exactly what causes this damage and why it does continue to be repaired when you are young. We do know about some of the contributing factors, though.

For example, our genes have an important role in the process. We have about 20,000 genes - bits of DNA that determine the way we look and how our bodies work. Over a lifetime, that genetic material is constantly being damaged by external and internal influences. Examples include UV radiation from the sun and substances (like free oxygen radicals) produced by the energy factories in the cells of your body (mitochondria). Most of the damage is repaired immediately. Our repair processes are not perfect, however, so some bits and pieces remain damaged. These small damages accumulate as we get older, contributing to the ageing process and in some cases causing age-related diseases.

Loss of telomeres

Scientists are also looking at “telomeres” as another cause of visible ageing. These are pieces of DNA that form a "cap" at the end of our chromosomes to protect them. Researchers have discovered that a small piece of telomere is lost each time a cell divides. Over time, the telomere becomes so short and fragile that cell division stops. The cells may then die or cause inflammation, speeding up the ageing process and possibly causing diseases.

Cells & molecules in trouble

Scientists have found many other cellular and molecular factors that contribute to the ageing process. For example we lose stem cells, which are essential for repairing damaged tissues and organs; it becomes increasingly difficult to maintain the condition of our proteins, the most important molecules in our cells; there is a decline in the quality of autophagy, the waste disposal system used in cells; and the list goes on and on.

In short, there is a lot going on in our bodies. All these factors cause us to age not only chronologically (in years), but also biologically (in looks).