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Most people will live khổng lồ experience aging. Age-related deterioration is affecting an ever-growing number of people. Although the process is unavoidable, it is important to understand the process. As a physiotherapist, we might be able to positively influence aspects that maintain or engender better health and wellness as a person ages, treating and ameliorating symptoms of common conditions associated with aging.

In the past, maximum life span (the maximum biological limit of life in an ideal environment) was not thought to lớn be subject khổng lồ change with the process of aging considered non-adaptive, và subject lớn genetic traits. In the early 1900s, a series of flawed experiments by researcher Alexis Carrel demonstrated that in an optimal environment, cells of higher organisms (chickens) were able khổng lồ divide continually, leading people lớn believe our cells lớn potentially possess immortal properties. In the 1960’s Leonard Hayflick<1> disproved this theory by identifying a maximal number of divisions a human cell could undergo in culture (known as the Hayflick limit), which mix our maximal life span at around 115 years. Life span is the key to the intrinsic biological causes of aging, as these factors ensure an individual’s survival to lớn a certain point until biological aging eventually causes death.

There are many theories about the mechanisms of age-related changes, và they are mutually exclusive, no one theory is sufficiently able khổng lồ explain the process of aging, & they often contradict one another. A literature review<2> highlights that centenarians have healthy ageing because of the delay in processes like physiological decline & age-related diseases or syndromes. The review discusses that genetic component which plays an important role in longevity. The researchers suggest that biology of centenarians yields a key for intervention to promote healthy ageing in the general population.

Modern biological theories of aging in humans currently fall into two main categories: programmed and damage or error theories. The programmed theories imply that aging follows a biological timetable (regulated by changes in gene expression that affect the systems responsible for maintenance, repair & defense responses), and the damage or error theories emphasize environmental assaults to lớn living organisms that induce cumulative damage at various levels as the cause of aging<3>.

These two categories of theory<4> are also referred to lớn as non-programmed aging theories based on evolutionary concepts (where ageing is considered the result of an organism’s inability to lớn better combat natural deteriorative processes), và programmed ageing theories (which consider ageing khổng lồ ultimately be the result of a biological mechanism or programme that purposely causes or allows deterioration & death in order lớn obtain a direct evolutionary benefit achieved by limiting lifespan beyond a species-specific optimum lifespan (Figure 1).


Figure 1: Evolutionary cost/ benefit of additional lifespan vs. Age.

Curve 1: Modern non-programmed aging theories – The evolutionary value of further life và reproduction is effectively zero beyond some species-specific age.Curve 2: Modern programmed aging theories – There is an evolutionary cost associated with surviving beyond a species-specific age.

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Goldsmith"s reviews of modern programmed (adaptive) theories of biological ageing investigates how organisms have evolved mechanisms that purposely limit their lifespans in order lớn obtain an evolutionary benefit.

Theories of Ageing

This video gives a good introduction to lớn the theories of aging


In his nhận xét of the modern theories of ageing, Jin<3> highlights three sub-categories of the programmed theory, và four sub-categories of the damage or error theory, & also relates some lớn how these might be observed in ageing populations.

Biological Theories of Aging

The Programmed Theory

1) Programmed Longevity, which considers ageing lớn be the result of a sequential switching on và 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 lớn control the pace of ageing. 3) Immunological Theory, which states that the immune system is programmed lớn decline over time, leading to lớn an increased vulnerability to infectious disease & thus ageing và death.

The Damage or Error Theory

1) Wear và tear theory, where vital parts in our cells và tissues wear out resulting in ageing. 2) Rate of living theory, that supports the theory that the greater an organism"s rate of oxygen basal, metabolism, the shorter its life span 3) Cross-linking theory, according lớn which an accumulation of cross-linked proteins damages cells and tissues, slowing down bodily processes & thus result in ageing. 4) free radicals theory, which proposes that superoxide and other không tính phí radicals cause damage khổng lồ the macromolecular components of the cell, giving rise to accumulated damage causing cells, & eventually organs, khổng lồ stop functioning.

Further Theories

Trindade et al<6> provide a different viewpoint again, stating that lớn understand the evolution of ageing, we have to understand the environment-dependent balance between the advantages and disadvantages of extended lifespan in the process of spreading genes. These researchers have developed a fitness-based framework in which they categorise existing theories into four basic types: secondary (beneficial), maladaptive (neutral), assisted death (detrimental), và senemorphic aging (varying between beneficial lớn detrimental).

Some of the more commonly discussed theories & their relation lớn ageing are summarised below:

Disengagement Theory<7>Refers khổng lồ an inevitable process in which many of the relationships between a person & other members of society are severed & those remaining are altered in quality.Withdrawal may be initiated by the ageing person or by society, & 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 và 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 vị not withdraw from society.This theory is recognised as the first formal theory that attempted to lớn explain the process of growing older.Activity Theory<8>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 lớn 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 và community roles.To maintain a positive sense of self the person must substitute new roles for those that are lost because of age. Và studies show that the type of activity does matter, just as it does with younger people.The Neuroendocrine Theory<9><10>First proposed by Professor Vladimir Dilman and Ward Dean MD, this theory elaborates on wear & 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 và glands khổng lồ 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 lớn them. Accordingly, as we age the secretion of many hormones declines & their effectiveness (compared unit to lớn unit) is also reduced due to lớn the receptors down-gradingThe không tính phí Radical Theory<9>Because the free radical molecule has an extra electron it creates an extra negative charge. This unbalanced energy makes the không tính tiền radical bind itself to another balanced molecule as it tries khổng lồ steal electrons. In so doing, the balanced molecule becomes unbalanced & thus a không tính phí radical itself.It is known that diet, lifestyle, drugs (e.g. Tobacco and alcohol) và radiation etc., are all accelerators of không tính phí radical production within the body.The Membrane Theory of AgingAs we grow older the cell membrane becomes less lipid (less watery and more solid). This impedes its efficiency khổng lồ conduct normal function and in particular there is a toxic accumulationThe Decline TheoryEnhancement và protection of the mitochondria is an essential part of preventing và slowing aging. Enhancement can be achieved with the above mention nutrients, as well as ATP supplements themselvesThe Cross-Linking Theory
Once this binding has occurred the protein becomes impaired and is unable to lớn perform as efficiently. Living a longer life is going lớn lead to the increased possibility of oxygen meeting glucose & protein and known cross-linking disorders include senile cataract & the appearance of tough, leathery và yellow skin.

Further information on video

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


Psychological Theories of Aging

The earliest known theories on aging were known lớn 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 lớn be influences by changing roles with age, relationship changes, status change in a society. <15>

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 & security, love và belongingness, self-esteem, và actualization. <15>


Individualism Theory

Proposed by Jung in 1960, Our personality evolves over time and is made up of ego và 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.<16>

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 & internal values. This theory focuses on the interconnectedness of individual & society.

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Selective Optimization và Compensation Theory

Proposed by Baltes in 1987. He believed that people over time learn lớn 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.<16><17>