The biology of ageing refers to the progressive accumulation of random molecular defects that accumulate in tissue and cells, which eventually result in age-related functional impairment of tissues and organs.
Genetic factors account for around 25% of the variance in human lifespan, and nutritional and environmental factors determine the rest.
A major accumulation of molecular damage is due to reactive oxygen species produced during the metabolism of oxygen to produce cellular energy. Oxidative damage results in:
- damage to nuclear chromosomal deoxyribonucleic acid (DNA)
- shortening of telomeres – ageing is associated with shortening of telomeres
- mitochondrial DNA and lipid peroxidation – this results in reduced cellular energy production, eventually causing cell death.
The rate at which damage occurs is variable, and the environment and nutrition have a role in oxidative damage in the ageing body. Insulin signalling pathways are important, and chronic inflammation is also important because it drives the production of reactive oxygen species.
Below is a list of the age-related physiological changes and associated clinical manifestations in various body systems. All information has been compiled from major physiology textbooks.1,2,3