THEORIES OF AGEING

Why do we get old? When do we start getting old? What are the signs of aging? Is there any limit to our aging? These questions are frequently pondered by mankind over the past two hundred years. However, despite recent advances in molecular biology and genetics, the mysteries that govern human life are yet to be unravelled.

Several theories have been proposed to explain the aging process, but none of them is completely satisfactory. Traditional theories of aging hold that aging is not an adaptation or genetically programmed. Aging proceeds at different rates in different species. Even within a species, rates of aging vary between individuals. A reasonable conclusion is that aging must be genetically controlled, at least to some extent. Within and between species, lifestyle and exposure can alter the aging process.

There are many theories of aging, but few are widely accepted. Some theories of aging focus on what controls the degenerative and entropic processes that occur with aging and why controls exist. Other theories focus on the evolutionary origins of aging. All these theories generally agree that aging does not confer a genetic advantage and develops primarily because it is not selected for. Broadly, we can classify the theories of aging in three major categories.

PSYCHOSOCIAL THEORIES

·      The earliest theories on aging came from the psychosocial disciplines, that does not explain the physical changes of aging.

·      They attempt to explain -

o   The changes in behaviour, personality, attitude, roles, and relationship that occur as individual age.
o   The Aging is a lifelong process characterized by transitions.

·      There are two kinds of theories – Sociological & Psychological

Sociological Theories

·         It relates these transitions to changing roles, relationships, and status within a culture or society impact an older adult’s ability to adapt.

·         Societal norms can affect how individuals perceive and enact their role within a community.

·         Some of the Sociological Theories are –

1.      Activity Theory

•      Given by Havighurst and Albrecht in 1953 and published in 1963.

•      “Activity is viewed by this theory as necessary to maintain a person’s life satisfaction and a positive self-concept”.

•      Theory based on assumptions:

–      Remaining occupied and involved is necessary to a satisfying late life i.e., it’s better to be active than inactive and happy than unhappy

–      an older individual is the best judge of his or her own success in achieving the first assumptions.

•      This theory proposes that activity is necessary for successful aging.

•      Active participation in physical and mental activities helps maintain functioning well into old age.

•      Purposeful activities and interactions that promote self-esteem improve overall satisfaction with life, even at the older age.

•      The continuation of activities performed during middle age is necessary for successful aging.

2.      Disengagement Theory

•      The highly controversial theory given by Cummings and Henry in 1961.

•      Aging is characterized by gradual disengagement from society and relationships.

•      This separation is desired by society and older adults that serves to maintain social equilibrium and promote internal reflection.

•      While the transition of responsibility from old to young maintains a continuously functioning society unaffected.

•      The outcome of disengagement is a new equilibrium that is ideally satisfying to both the individual and society.

•      This theory is no longer supported.

3.      Subculture Theory

•      Proposed by Arnold M. Rose in 1965.

•      Accordingly, to protect older adults from a unique subculture within society from society's negative attitudes towards aging as well as the loss of status.

•      According to the dissection theory, Rose argued that subculture occurs as a response to loss of status. Older adults are in that subculture with their own norms and beliefs, and they like to interact with each other.

•      In the subculture, individual status is based on health and mobility rather than education, occupation, and economic achievement.

•      Older adults therefore suffer a social disadvantage in relation to status and associated esteem due to the functional decline that occurs with aging.

4.      Age Stratification Theory

•      Proposed by Riley and colleagues, 1972

•      Society is stratified into different age categories that are the basis for acquiring resources, roles, status, and deference from others in society.

•      In addition, they observed that age cohorts are influenced by the historical context in which they live and can vary across generations.

•      People born in the same cohort have similar experiences, ideologies, orientations, attitudes, and values as well as expectations regarding the timing of life transitions such as retirement and life expectancy.

•      This theory highlighted the importance of cohorts and the associated socioeconomic and political impact on how individuals age.

5.      Person-Environment-Fit Theory

•      Proposed by Lawton’s, 1982

•      Person-Environment Psychology suggests that a reciprocal relationship exists between people and environments.

•      Capacity to function in one’s environment is an important aspect of successful aging, and that function is affected by ego strength, motor skills, biologic health, cognitive capacity, and sensory-perceptual capacity, as well as external conditions imposed by the environment.

•      Functional capacity influences an older adult’s ability to adapt to his or her environment. Those individuals functioning at lower levels can tolerate fewer environmental demands.

6.      Continuity Theory

•      Proposed by Robert C. Atchley, 1989

•      Continuity Theory suggests that personality is well developed by the time we reach old age and tends to remain consistent throughout our lives. i.e., How a person has been throughout life is how that person will continue through the remainder of life

•      Old age is not a separate phase of life, but rather a continuation and thus an integral component.

•      Personality influences roles and life satisfaction and remains consistent throughout life.

•      Personality remains the same and the behaviours become more predictable as people ages.

•      Past coping patterns recur as older adults adjust to physical, financial, and social decline and contemplate death.

•      Identifying with one’s age group, finding a residence compatible with one’s limitations, and learning new roles postretirement are major tasks.

•      The first sociological theory to acknowledge that responses to aging differ among individuals.

7.      Gerotranscendence Theory

•      Proposed by Tornstam’s, 1994

•      One of the newest sociological aging theories.

•      This theory proposes that aging individuals undergo a cognitive transformation from a materialistic, rational perspective toward “oneness” with the universe.

•      Characteristics of successful transformation include a more outward or external focus, accepting impending death without fear, an emphasis on substantive relationships, a sense of connectedness with preceding and future generations and spiritual unity with the universe.

•      Gerotranscendence borrows from disengagement theory but does not accept its idea that social disengagement is a necessary and natural development. Rather, Tornstam asserted that activity and participation must be the result of one’s own choices and that control over one’s life in all situations is essential for successful adaptation to aging.

Psychological Theories

•      Psychological theories are concerned with the development of the personality or ego and the transition with the challenges associated with different life stages.

•      Explain aging in terms of mental processes, emotions, attitudes, motivation, and personality development that is characterized by life stage transitions.

  •      Some of the Psychological Theories are –

1.      Human Needs Theory

•      Maslow (1954), a psychologist, published the human needs theory.

•      In this theory, Maslow surmised that a hierarchy of five needs motivates human behaviour: physiologic, safety and security, love and belonging, self-esteem, and self-actualization.

•      These needs are prioritized such that more basic needs like physiological functioning or safety take precedence over personal growth needs (love and belonging, self-esteem, and self-actualization).

•      Movement is multidirectional and dynamic in a lifelong process toward need fulfilment.

•      Self-actualization requires the freedom to express and pursue personal goals and be creative in an environment that is stimulating and challenging.

•      Maslow asserted that failure to grow leads to feelings of failure, depression, and the perception that life is meaningless.

2.       Theory of Individualism

•      Jung (1960) proposed the Theory of Individualism.

•      According to that our personality develops over a lifetime and is composed of an ego or self-identity that has a personal and collective unconsciousness that views life from a personal or external perspective.

•      Personal unconsciousness is the private feelings and perceptions surrounding important persons or life events.

•      Collective unconscious is shared by all persons. It contains latent memories about human origin.

•      The collective unconscious is the foundation of personality on which the personal unconsciousness and ego are built. Jung’s theory says that people tend to view life through either their own “lens” (introverts) or the lens of others (extroverts).

•      As individuals age, they begin to reflect on their beliefs and life accomplishments. According to Jung, one ages successfully when he or she accepts the past, adapts to physical decline, and copes with the loss of significant others.

•      Older adults search for life meaning and adapt to functional and social losses.

3.       Stages of Personality Development Theory

•      According to Erikson (1963), personality develops in eight sequential stages with corresponding life development tasks. Each stage has a life task at which we may succeed at or fail.

•      The eighth phase, integrity versus despair, is characterized by evaluating life accomplishments; struggles include letting go, accepting care, detachment, and physical and mental decline. Satisfaction leads to integrity, while dissatisfaction creates a sense of despair.

•      In nursing, Erikson’s model is often used as a framework to examine the challenges faced by different age groups. She found that older adults who expressed higher levels of meaning and energy described a sense of connectedness, self-worth, love, and respect that was absent among participants who felt unfulfilled.

•      This finding is consistent with the positive or negative outcome that may result from Erikson’s develop-mental stage, “integrity versus despair.” 

4.       Life-Course / Life Span Theory

•      Life-course Theory is concerned with understanding age group norms and their characteristics.

•      life course is defined as a sequence of socially defined events and roles that the individual enacts over time.

•      The central theme of life course is that life occurs in stages that are structured according to one’s roles, relationships, internal values, and goals.

•      Individuals adapt to changing roles and relationships that occur throughout life, such as getting married, finishing school, completing military service, getting a job, and retiring.

•      Goal achievement is linked to life satisfaction, but people’s goals are limited by external factors.

•      Successful adaptation to life changes may require revising one’s beliefs to be consistent with society’s expectations.

•      The life-course perspective remains a dominant theme in the psychology literature today.

5.       Selective Optimization with Compensation Theory

•      Baltes’s (1987) theory of successful aging emerged from his study of psychological processes across the lifespan. He asserted that individuals learn to cope with the functional losses of aging through the processes of selection, optimization, and compensation.

•      Aging individuals adjust activities and roles as limitations present themselves; at the same time, they choose those activities and roles that are most satisfying (optimization).

•      Coping with illness and functional decline may lead to greater or lesser risk of mortality. Ideally, selective optimization with compensation is a positive coping process that facilitates successful aging.

BIOLOGIC THEORIES

•      Biologic theories concerned with answering basic questions regarding the physiological processes that occur in all living organisms as they chronologically age.

•      Attempt to explanations of:

•      deleterious effects leading to decreasing function of the organism

•      gradually occurring age-related changes that are progressive over time because of their biologic structure.

•      intrinsic changes that can affect all member of a species because of chronologic age

•      Many of the biologic theories of aging overlap because most assume that the changes that cause aging occur at a cellular level.

•      Each theory attempts to describe the processes of aging by examining various changes in cell structures or function.

•      Biologic theories are divided into two groups –

Non-stochastic Theories

•      View aging as certain predetermined, timed phenomena

•      Explain aging as genetically programmed physiological mechanisms within the body control of the process of aging.

•         Programmed theory

•         Everyone has a biologic clock

•         Each individual has a genetic program specifying with predetermined number of cell divisions.

•         As the program plays out, the person experiences predictable changes

•         Run-out-of-program theory

•         Every person has a limited amount of genetic material

•         Will run out eventually

•         Rate of living theory

•         Individuals have a finite number of breaths or heartbeats that are used up over time.

•         Gene theory

•         Proposes the existence of one or more harmful genes that activate over time, resulting in the typical changes seen with aging and limiting the life span of the individual.

•         Immunity Theory

•         Immuno-senescence: Age-related functional diminution of the immune system

•         Lower rate of T-lymphocyte (“killer cells”) proliferation in response to a stimulus & therefore a decrease in the body’s defense against foreign pathogens.

Stochastic Theories

•      Explain aging as events that occur randomly and accumulate over time

•      aging as the result of random cellular damage that occurs over time.

Molecular Theories - aging is controlled by genetic materials that are encoded to predetermine growth and decline.

•      Error Theory

•      Errors can occur in the transcription in any step of the protein synthesis of DNA

•      Error causes the reproduction of an enzyme or protein that is not an exact copy

•      As transcription errors to occur, the end product would not even resemble the original cell, thereby compromising its functional ability.

•      Somatic Mutation Theory

•      The accumulation of mutations in the genetic material of somatic cells as a function of time results in a decrease in cellular function.

•      Aging results from deoxyribonucleic acid (DNA) damage caused by exposure to chemicals or radiation and that this damage causes chromosomal abnormalities that lead to disease or loss of function later in life.

Cellular Theories - aging is a process that occurs because of cell damage. When enough cells are damaged, overall functioning of the body is decreased.

•      Free Radical Theory

•      Free radicals are by-products of metabolism-can increase as a result of environmental pollutants

•      When they accumulate, they damage cell membrane, DNA, and the immune system, decreasing its efficiency

•      The body produces antioxidants that scavenge the free radicals

•      Cross-Linkage Theory

•      AKA Connective tissue theory/ glycosylation theory

•      Some proteins in the body become cross-linked, thereby not allowing for normal metabolic activities

•      Cell molecules from DNA and connective tissue interact with free radicals to cause bonds that decrease the ability of tissue to replace itself.

•      Result: tissues do not function at optimal efficiency

•      For e.g., skin changes typically attributed to aging such as dryness, wrinkles, and loss of elasticity.

•      Clinker Theory

•      Combines the somatic mutation, free radical, and crosslink theories

•      Suggest that chemicals produced by metabolism accumulate in normal cells and

•      Cause damage to body organs, such as the muscles, heart, nerves, and brain.

•      Wear & Tear Theory

•      Cells simply wear out over time because of continued use-rather like a machine

•      As people age, their cells, tissues, and organs are damaged by internal or external stressors.

•      Result: overall functioning decreases

Emerging Biologic Theories of Aging

•      Neuroendocrine (Pacemaker) Theory

•      Proposed by Prof. Vladimir Dilman and Ward Dean MD

•      “…examines the interrelated role of the neurologic and endocrine systems over the life-span of an individual”.

•      there is a decline, or even cessation, in many of the components of the neuroendocrine system over the lifespan

•      Metabolic Theory/Caloric Restriction

•      “…proposes that all organisms have a finite amount of metabolic lifetime and that organisms with a higher metabolic rate have a shorter lifespan”.

•      Rodent-based research has demonstrated that caloric restriction increases the lifespan and delays the onset of age-dependent diseases

•      DNA-Related Research

•      Mapping the human genome (“…there may be as many as 200 genes responsible for controlling aging in humans”)

•      Discovery of telomeres

•      Telomere length shortens with age. Progressive shortening of telomeres leads to senescence, apoptosis, or oncogenic transformation of somatic cells, affecting the health and lifespan of an individual.

NURSING THEORIES 

•      Many classic theories that describe biological, social, and psychological aging,

•      None of these gives us dimensions of aging into a holistic theory.

•      Nurses address all aspects of the person, theories that offer the holistic perspective would be valuable in guiding nursing care.

•      In an effort to address this need, several nurses have recently developed theories of aging.

Functional Consequences Theory

•      Environmental and biopsychosocial consequences impact functioning.

•      Nursing’s role is risk reduction to minimize age-associated disability in order to enhance safety and quality of living. 

Theory of Thriving

•      Failure to Thrive results from a discord between the individual and his or her environment or relationships.

•      Nurses identify and modify factors that contribute to disharmony among these elements.

Theory of Successful Aging

•      Aging well is defined by the extent to which older adults adapt to the cumulative physical and functional changes they experience.

•      Flood proposed that:

–      aging is a progressive process adaptation,

–      aging may be successful or unsuccessful, depending upon a person’s ability to cope,

–      successful aging is influenced by a person’s choices, and

–      aging people experience changes, which uniquely characterize their beliefs and perspectives in ways that differ from those of younger adults.

•      According to this theory, aging successfully means physically, psychologically, and socially engaged in meaningful ways that are individually defined, and along with that achieving a comfortable acceptance of impending death.

CONCLUSION

•      For older adults with chronic illnesses, stochastic theories of aging help nurse to better manage physical illness and conditions.

•      Psychosocial aging theories help nurses assist older adults and their families recognize that their life has been one of integrity and meaning and facilitate peaceful death with dignity.

•      Aging continues to be explained from multiple theoretical perspectives, which collectively reveal that aging is a complex phenomenon still much in need of research.

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