What is ageing?

They say that age is just a number. And it's true. If and 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 rising for years and has doubled for both men and women in the industrialized countries over the last 120 years [1]. In Germany life expectancy is over 83 years for new-born girls and over 78 years for new-born boys [2]. In addition, there are now more than 500,000 people worldwide who are 100 years old or older - a number that has more than tripled within the last 20 years [3]. The age record is held by the French woman Jeanne Louise Calment: she died on August 4, 1997 at the age of 122 years and 164 days. Indeed, many researchers consider an age of about 120 years to be a natural upper limit for humans [4]. This is based on the observation that while average life expectancy has increased over the last century, maximum life expectancy has not changed and has remained almost constant around 120 years.

However, age and ageing are two different things. Age is initially only a number and is often subjectively assessed. Ageing, on the other hand, is a process that can be observed and scientifically described and defined. In ageing research ageing is defined as progressive loss of physiological integrity, leading to impaired function and increased vulnerability to death [5].

The classic, verifiable ageing processes such as the appearance of wrinkles and the decrease in performance and endurance appear from 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 [6]. Further factors are individual lifestyle and external environmental influences.

Further reading:

Sources:

  1. Max Roser, E.O.-O.a.H.R. Life Expectancy. Our World in Data 2013.
  2. Statistisches Bundesamt (Destatis). Durchschnittliche Lebenserwartung (Periodensterbetafel). 2020.
  3. Duffin, E. Number of centenarians worldwide 2010-2100. 2019.
  4. Dong, X., B. Milholland, and J. Vijg, Evidence for a limit to human lifespan. Nature, 2016. 538(7624): p. 257-259.
  5. López-Otín, C., et al., The hallmarks of aging. Cell, 2013. 153(6): p. 1194-217.
  6. Melzer, D., L.C. Pilling, and L. Ferrucci, The genetics of human ageing. Nature Reviews Genetics, 2020. 21(2): p. 88-101.

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