Theories of Ageing

Original Editor - Bhanu Ramaswamy as part of the AGILE Project.

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Introduction

Ageing is a ubiquitous, intrinsic and ongoing process. Theories of aging have been debated since the time of the ancient Greeks, and researchers now concluding that no one theory exists that explains all aspects of aging. Instead scientists have found that several theories may be combined to explain various aspects of the complex phenomena we call aging .

This video gives a good introduction to the theories of aging

Biological Theories of Ageing

Biologic theories are concerned with answering questions regarding the physiologic processes that occur in all living organisms as they chronologically age. These age-related changes arise independent of any external or pathologic effects, and the quest is to uncover these inciting factors that cause the actual aging process in organisms.

Modern biological theories of aging in humans currently fall into two main categories:

1. Programmed theories imply that aging follows a biological timetable (regulated by changes in gene expression that affect the systems responsible for maintenance, repair and defense responses). Are the result of a biological programme that purposely causes or allows deterioration and death in order to obtain a direct evolutionary benefit achieved by limiting lifespan beyond a species-specific optimum lifespan
2. Non-programmed aging theories (damage or error theories) emphasize environmental assaults to living organisms that induce cumulative damage at various levels as the cause of aging. Based on evolutionary concepts (where ageing is considered the result of an organism’s inability to better combat natural deteriorative processes)which consider ageing to ultimately be the result of a biological mechanism or programme that purposely causes or allows deterioration and death in order to obtain a direct evolutionary benefit achieved by limiting lifespan beyond a species-specific optimum lifespan.

The Programmed Theory

1. Programmed Longevity, which considers ageing to be the result of a sequential switching on and off of certain genes, with senescence being defined as the time when age-associated deficits are manifested.
   
2. Endocrine Theory, where biological clocks act through hormones to control the pace of ageing.
   
3. Immunological Theory, which states that the immune system is programmed to decline over time, leading to an increased vulnerability to infectious disease and thus ageing and death.

Non-programmed/ Damage or Error Theory

1. Error theory: based on the idea that errors can occur in the transcription of the synthesis of DNA. These errors are perpetuated and eventually lead to systems that do not function at the optimum level. The organism’s aging and death are attributable to these events (Sonneborn, 1979).
2. The Free Radical Theory: This now very famous theory of aging was developed by Denham Harman MD at the University of Nebraska in 1956. The term free radical describes any molecule that has a free electron, and this property makes it react with healthy molecules in a destructive way. Because the free radical molecule has an extra electron it creates an extra negative charge. This unbalanced energy makes the free radical bind itself to another balanced molecule as it tries to steal electrons. In so doing, the balanced molecule becomes unbalanced and thus a free radical itself. It is known that diet, lifestyle, drugs (e.g. tobacco and alcohol) and radiation etc., are all accelerators of free radical production within the body.
3. The Cross-Linking Theory: also referred to as the Glycosylation Theory of Aging. In this theory it is the binding of glucose (simple sugars) to protein, (a process that occurs under the presence of oxygen) that causes various problems. Once this binding has occurred the protein becomes impaired and is unable to perform as efficiently. Living a longer life is going to lead to the increased possibility of oxygen meeting glucose and protein and known cross-linking disorders include senile cataract and the appearance of tough, leathery and yellow skin.
4. The Neuroendocrine Theory First proposed by Professor Vladimir Dilman and Ward Dean MD, this theory elaborates on wear and tear by focusing on the neuroendocrine system. This system is a complicated network of biochemicals that govern the release of hormones which are altered by the walnut sized gland called the hypothalamus located in the brain. The hypothalamus controls various chain-reactions to instruct other organs and glands to release their hormones etc. The hypothalamus also responds to the body hormone levels as a guide to the overall hormonal activity. But as we grow older the hypothalamus loses it precision regulatory ability and the receptors which uptake individual hormones become less sensitive to them. Accordingly, as we age the secretion of many hormones declines and their effectiveness (compared unit to unit) is also reduced due to the receptors down-grading
5. The Membrane Theory of Aging The membrane theory of aging was first described by Professor Imre Zs.-Nagy of Debrechen University, Hungary. According to this theory it is the age-related changes of the cell's ability to transfer chemicals, heat and electrical processes that impair it. As we grow older the cell membrane becomes less lipid (less watery and more solid). This impedes its efficiency to conduct normal function and in particular there is a toxic accumulation
6. The Decline Theory: The mitochondria are the power producing organelles found in every cell of every organ. Their primary job is to create Adenosine Triphosphate (ATP) and they do so in the various energy cycles that involve nutrients such as Acetyl-L-Carnitine, CoQ10 (Idebenone), NADH and some B vitamins etc. Enhancement and protection of the mitochondria is an essential part of preventing and slowing aging. Enhancement can be achieved with the above mention nutrients, as well as ATP supplements themselves.

Further information on video

In addition to these explanations, you can see several presentations about the biological theories of ageing on YouTube:  

A 14 minute video on the Wear and Tear theory, free radical theory, somatic mutation theory and programmed theory of ageing.

The ageing Academy’s series on Aging: Stem Cells, long Lived Proteins, Cell Programming, Gene Expression:

A Big Think monologue by Michio Kaku looking at what enzymes like Telomerase and Resveratrol offer:

• See also - Policy and Initiatives Focused on the Older Population
  

Psychological and Psychosocial Theories of Aging

The earliest known theories on aging were known to be psychological theories. As the age increases these theories deals with the changes in the behavior, attitude towards life and personality modifications or ego development in an individual. The psychological theories of aging focus on the changes in mental processes, emotions, attitudes, motivation and personality adaptations as per the physical, social or environmental demands. This ability of adaptation is believed to be influences by changing roles with age, relationship changes, status change in a society.

Human Needs Theory

Developed by Maslow in 1954, this theory focuses on the fact that human behavior is motivated by their needs with age. These needs are; physiological, safety and security, love and belongingness, self-esteem, and actualization.

• Physiological needs: The desire to obtain food, water, and shelter is great, and the type of behaviors that ensure these things are reinforced. Most people don't need help with this, but some people, particularly those with cognitive disabilities, may need it.
• Safety and Security: This kind of need has both short-term and long-term repercussions, such as staying away from harmful places and attempting to establish a safer society. These are more abstract requirements than food, water, and shelter, and continuing to seek them requires some projective reasoning. While hunger, thirst, and exposure to the elements are instinctive, it can be difficult to notice and adjust to subtle threats to safety or security. Because the rewards of acquiring food are immediate and visceral, the sorts of training connected with these requirements are also significantly different than those related with physical needs, because the need for security is often realized only when it is threatened or lost.
• Belongingness and Love: The capacity to interact via phone, e-mail, or social networking sites significantly boosts the chances of belonging. Families of patients with cognitive impairments frequently seek out ways to meet their loved ones' demands for belonging and love, remaining "virtually" connected across location and time. Patients with even severe cognitive disabilities value human contact because the rewards of belonging and affection are quick and straightforward.
• Esteem needs: People want to be believed in and respected. In terms of money, this entails accomplishing activities that a person values. Restricting someone's ability to engage in such activities can lower their self-esteem.
• Self-actualization needs: Being loyal to one's own nature and pursuing self-fulfillment via creativity are the greatest levels of human wants. When all previous levels of need have been met, self-actualization can be attained by engaging in things that make you feel fully alive or participating in something with greater meaning. Artistic interests, professional jobs, humanitarian activities, social projects, and hobbies, as well as mature and tolerant attitudes to dealing and communicating, are all ways to meet this desire.

Individualism Theory

Proposed by Jung in 1960, Our personality evolves over time and is made up of ego and self-identity, which are both personal and collectively unconscious. A private emotion or perception surrounding important people or life events is known as personal unconsciousness.

Life-Course (Lifespan development) Theory

Came into existence in 1980s by behavioral psychologists who decided to shift from personality development as the basis of understanding aging to the concept of ‘life course’. This theory divides life course into predictable pattern of stages that are formed according to goals, relationships and internal values. This theory focuses on the interconnectedness of individual and society.

Selective Optimization and Compensation Theory

Proposed by Baltes in 1987. He believed that people over time learn to cope up with the individual losses of aging through a process of selection, optimization and compensation. As an individual age, the adaptation is done by the process of optimizing more satisfying roles in life. Baltes believes that selected optimization combined with compensation is a healthy coping strategy that helps people age successfully.

Disengagement Theory

• Refers to an inevitable process in which many of the relationships between a person and other members of society are severed & those remaining are altered in quality.
• Withdrawal may be initiated by the ageing person or by society, and may be partial or total.
• It was observed that older people are less involved with life than they were as younger adults.
• As people age they experience greater distance from society & they develop new types of relationships with society.
• In America there is evidence that society forces withdrawal on older people whether or not they want it.
• Some suggest that this theory does not consider the large number of older people who do not withdraw from society.
• This theory is recognised as the first formal theory that attempted to explain the process of growing older.

Activity Theory

• Is another theory that describes the psychosocial ageing process.
• Activity theory emphasises the importance of ongoing social activity.
• This theory suggests that a person's self-concept is related to the roles held by that person i.e. retiring may not be so harmful if the person actively maintains other roles, such as familial roles, recreational roles, volunteer & community roles.
• To maintain a positive sense of self the person must substitute new roles for those that are lost because of age. And studies show that the type of activity does matter, just as it does with younger people