Theories of ageing

Biological Theories of ageing:


Genetically programmed Theory

Ageing is an essential and innate part of the biology of people, and that ageing is programmed into our body systems. The three main systems that are connected with ageing are the endocrine (hormonal) system, the immune system and our genes. These systems change over time. These changes cause the symptoms and signs of ageing, such as wrinkles and memory loss.


We like to compare the human body to a machine. But this is not a very good comparison. Unlike a machine, which has only the parts it was built with, the human body continually repairs and replaces cells. Every seven years, 90 percent of the cells in your body are new. The human body is an amazing, open, dynamic system. To understand ageing, we have to forget about machines and think about living systems.

Studies have demonstrated that genetics can play a major role in ageing. When researchers adjust the genes in certain mice, yeast cells and other organisms, they can almost double the lifespan of these creatures. The meaning of these experiments for people is not known, but researchers think that genetics account for up to 35 percent of the variation in ageing among people. Some key concepts in genetics and ageing include:

  • Longevity Genes: There are specific genes which help a person live longer.

  • Cell Senescence: The process by which cells deteriorate over time.

  • Telomeres: Structures on the end of DNA that eventually are depleted, resulting in cells ceasing to replicate.

  • Stem Cells: These cells are unspecialised cells that can become any type of cell in the body and hold promise to repair damage caused by ageing.


Genetic theory of ageing

The genetic theory of ageing believes that lifespan is largely determined by the genes we inherit. According to the theory, our potential age is primarily determined at the moment of conception. There is some evidence to support this theory. People with parents who have lived long lives are more likely to live long themselves (though this could be partially explained by learned behaviours, such as food preferences). Also, twin studies have shown that identical twins (who have the exact same genes) have closer lifespans than siblings.


Disposable soma theory

The disposable soma theory, proposed in 1977 by Thomas Kirkwood, presumes that the body must budget the amount of energy available to it. The body uses food energy for metabolism, reproduction, repair and maintenance. The theory that ageing is caused by the body having increasingly less resources to allocate towards repairing wear and damage to tissues.

This theory also, in effect, combines the apparent declining force of natural selection after breeding age is reached with accumulation of damage, and suggests a relationship between reproduction and lifespan. The disposable soma theory is one of those based on the idea that the evolutionary value of additional life declines following the age at which an organism achieves reproductive maturity.


Gender differences theory

The theory explains that there are many reason for gender differences in ageing. It is a simple fact that, almost everywhere in the world, women live longer than men. Some think that the reason for longer life expectancy for women is that men do more dangerous things and have more dangerous occupations (being in the armed forces, for example). That explains some, but not all, of the differences. Other explanations include the fact that women are more likely to see a doctor and (possibly) be diagnosed earlier for health problems. Sex and ageing are also very different for men and women. A woman's body responds to ageing dramatically (with menopause and puberty) while a man's body responds more gradually.


Psychosocial theories of ageing:


Disengagement theory

Disengagement theory is a theory that older people will need to withdraw from social contact with others. Older people will disengage because of reduced physical health and loss of social opportunities.


Social engagement means being involved with people or activities. Therefore, disengagement means to withdraw from involvement. In 1961, two authors called Cumming and Henry put forward the disengagement theory that older people would naturally tend to withdraw from social involvement with others as they get older; Older people tend to have restricted opportunities to interact with others for example, ill health may cause poor mobility or problems with hearing or vision thus making interaction with other people more difficult. Geographical mobility may also play a part in the reduction in interaction as many people retire and move away from friends and family.

Retirement from work may mean less contact with colleagues in a social setting.

Travel and technology may be a factor for the reduction in social engagement because some older people do not have access to a car, the Internet or a mobile phone.


Cumming(1975) argued that older people would experience a reduction in social contact as they grew older and become increasingly 'individual' and less concerned with the expectations of others. He argued that it was appropriate and healthy for older people to withdraw from others because he saw disengagement as a natural part of ageing.

The theory of disengagement was widely accepted in the past. For example, Bromley(1974) argued that 'although some individuals fight the process all the way, disengagement of some sort is bound to come, simply because older people have neither the physical nor mental resources they had when they were young.'


Activity theory

This is a theory which argues that older people need to stay mentally and socially active in order to limit the risks associated with disengagement.

This major theory has been argued that older people needed to disengage, but that they also needed to remain ‘active’ in order to prevent disengagement going too far. This means that older people need to withdraw from society, however, not to the extent where they find it difficult to communicate with anyone.

Bromley said ‘They need to be educated to make use of them and encouraged to abandon apathetic attitudes and fixed habits.’ This was said because older people need to ensure that they do not become too withdrawn and in order to do that they need to be educated so that they do not fall into bad attitudes and habits as too much disengagement would lead to ‘stagnation’ and a loss of mental and physical skills.