What is ageing?

They say age is just a number. And that is true. Whether or when someone is old cannot be answered at all, because this is a purely subjective feeling. You are only as old as you feel. Average life expectancy has been increasing for years and has doubled for both men and women in industrialised countries over the last 120 years [Roser, M. et al.]. In Germany, life expectancy for newborn girls is over 83 years and for newborn boys over 78 years [Federal Statistical Office (Destatis).]. In addition, there are now more than 500,000 people worldwide who are 100 years or older - a number that has more than tripled in the last 20 years [Duffin, E.]. The age record is held by Frenchwoman Jeanne Louise Calment: she died on 4 August 1997 at the age of 122 years and 164 days. In fact, many researchers consider an age of about 120 years to be a natural upper limit for humans  [Dong, X. et al.]. This is based on the observation that while average life expectancy has increased over the last century, maximum life expectancy has not changed and remains almost constant at around 120 years.

However, age and ageing are two different things. Age is initially just a number and is often judged subjectively. Ageing, on the other hand, is a process that can be observed and scientifically described and defined. In ageing research, ageing is defined as a progressive loss of physiological integrity that leads to functional impairments and an increased probability of death [López-Otín, C. et al.].

The classic, verifiable ageing processes such as the appearance of wrinkles and the decline in performance and stamina occur around the age of 20. How quickly and continuously the ageing process proceeds is influenced by several factors. Genetic factors determine the ageing process of a person to about 10-15 percent [Melzer, M. et al.]. Other factors include individual lifestyle and external environmental influences.

References:

• Roser, M., et al., Life Expectancy. Our World in Data 2013.
• Federal Statistical Office (Destatis). Average life expectancy (period mortality table). 2020.
• Duffin, E., Number of centenarians worldwide 2010-2100. 2019.
• Dong, X., et al., Evidence for a limit to human lifespan. Nature, 2016. 538(7624): p. 257-259.
• López-Otín, C., et al., The hallmarks of aging. Cell, 2013. 153(6): p. 1194-217.
• Melzer, D., et al., The genetics of human ageing. Nature Reviews Genetics, 2020. 21(2): p. 88-101.

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