Gerontology Module 1B - Theories of Aging PDF

 Biological Theories: Biological Theories of Aging-Biological theories attempt to explain physical aging as an involuntary process, which eventually leads to cumulative changes in cells, tissues and fluid.  Intrinsic Theory- Intrinsic biological theory maintains that aging changes ari...

 Biological Theories: Biological Theories of Aging-Biological theories attempt to explain physical aging as an involuntary process, which eventually leads to cumulative changes in cells, tissues and fluid.  Intrinsic Theory- Intrinsic biological theory maintains that aging changes arise from internal, predetermined causes. Several theories assume that individuals inherit a genetic program that determines their specific life expectancy. In fact, various studies have shown a positive relationship between parental age and filial life span. Genetic mutations are also thought to be responsible for aging, a pattern depicted below, laboratory experiments which have accelerated mutation rates have not produced proportionate increases in the rate of aging, thus reducing support of this theory. Some theorists believe that a growth substance fails to be produced causing the cessation of cell growth and reproduction.  Extrinsic Biological Theory- Extrinsic biological theory maintains that environmental factors lead to structural alterations, which, in turn, cause degenerative changes. Disease producing organisms are often associated with biological aging. Bacteria, fungi, viruses, and other organisms are thought to be responsible for certain physiological changes during the aging process. Although no conclusive evidence presently exists to link these pathogens with the aging process, interest in this theory has been stimulated by the fact that humans and animals have been shown to live longer with the control or elimination of certain pathogens viaimmunization and the use of antimicrobial  Programmed theories 1. Programmed Senescence Theory / Hayflick Limit Theory According to Hayflick, old age sets in, when the body cells exhaust the capacity of undergoing multiplication.  In 1950’s Hayflick Suggested that the human cell is limited in no. of times it can divide, he theorized that it can divide 50 times, after which they simply stop dividing (and hence die). He showed that nutrition has an effect on cells, with overfed cells dividing much faster than underfed cells, as cells divide to help repair and regenerate themselves. The Hayflick Limit indicates that there is a need to slow down the rate of cell division if we want to live long lives. Cell division can be slowed down by diet and lifestyles etc. 2. Neuroendocrine Control Theory The age-related changes in response to hormones may be the result of changes in the receptors for hormones rather than changes in the activity of the endocrine hormones themselves. First proposed by Prof. Vladimir Dilman& Ward Dean MD. The Endocrine theory states that, as we age, the endocrine system becomes less efficient and eventually leads to the effects of aging. Hormones level are affected by factors such as stress and infection. 3. Immunologic Theory According to this theory, the rate of aging is controlled by the immune system. This theory states that, as we age the no. of cells start to decrease becoming less functional.  Error Theories 1. Wear & Tear theory Early Theory on aging proposed that there is a fixed storage of energy available to the body. As time passes, the energy is depleted and because it cannot be restored, the person dies. Later, other theories emerged.Theory compares the human body to a machine that simply wears out as a result of constant use. Body cells, structures and functions wear out or are over used through exposure to internal and external stressors. Effects from the residual damage accumulate, the body can no longer resist stress and death occurs. Repeated injury or overuse; internal and external stressors, including trauma, chemicals and build-up of naturally occurring waste. The effects of aging are caused by progressive damage to cells and body systems over time. This was not widely accepted. 2. Cross link theory It also referred to as the glycosylation theory of aging, was proposed by Johan Bjorksten in 1942. According to this theory, an accumulation of cross- linked proteins damages cells and tissues, slowing down bodily processes resulting in aging. It explains aging in terms of the accumulation of errors by cross- linking, or the stiffening of proteins in the cell. Proteins link with glucose and other sugars in the presence of oxygen and become stiff and thick. The cross-link theory and connective tissue theory asserts that the molecules of collagen and elastin, connective tissue components, from bonds that increase cell rigidity. Cross linkage is thought to results from chemical reaction that creates chemical bonds between normally separate molecules in the body. 3. Free radical theory Proposed by Denham Harman in 1956. It states that organisms age because cells accumulate free radical damage over time. A free radical is any atom or molecule that has a single unpaired electron in an outer shell. Free-radicals are molecule with an extra cellular charge. This charge creates a reaction that alters the structure or function of the cell membrane. Free radical is unstable, short lived and highly reactive, as they attack nearby molecules in order to steal their electrons and gain stability, causing radical chain reactions to occur. Increased unstable free-radicals produces effect harmful to biological systems, such as chromosomal changes, pigment accumulation and collagen alteration Free-radical theory emphasizes the mechanism of oxygen use at the cellular level. Free radicals are natural by products of cellular activity and are always present to some extent. With ageing, the damage caused by free radicals occurs faster than the cells can repair themselves, and cell death occurs. 4. Error catastrophe theory Proposed by Leslie Orgel in 1963. It states that aging is the result of the accumulation of errors in cellular molecules that are essential for cellular function and reproduction that eventually reaches a catastrophic level that is incompatible with cellular survival. Catastrophe means a sudden event causing damage or suffering. 5. Somatic Mutation Theory This theory suggests that cells exposed to chemicals or radiation results in alteration within the DNA molecule. Mutation results from these alterations accumulate overtime and become more evident with age and increasing cellular impairment. It states that an important part of aging is determined by what happens to our genes after we inherit them. From the time of conception, our body’s cells are continually reproducing. Additionally, exposures to toxins, radiation or UV light can cause mutations in the body’s genes. The body can correct or destroy most of the mutations, but not all of them. Eventually, the mutated cells accumulate, copy themselves and cause problems in the body’s functioning related to aging.  Psychological Theories: Psychological and social changes during the aging process are closely united, and they have a significant impact on each other. It is difficult to explain mental processes,behaviour and feelings without the perspective of social roles,positions and norms. A theory of aging that is purely social or psychological would be most unusual, and it is more appropriate to approach these aging factors as psychosocial theories. Probably the most controversial and widely discussed is the disengagement theory, developed by Elaine Cumming and William Henry. This theory views aging as a process whereby society and individual gradually withdraw or disengage, from each other, to the mutual satisfaction and benefit for both. The benefit to individual is that they can reflect and be centred on themselves, having been freed from societal roles. The value of disengagement for society is that some orderly means is established for the transfer of power from old to young, making it possible to society to continue functioning after its individual members have died. 1. Personality Theory  These theories address aspects of psychological growth without delineating specific tasks or expectations of older adults. Some evidence suggests that personality characteristics in old age are highly correlated with early life characteristics. 2. Development task Theory The developmental tasks are activities and challenges that one must accomplish at specific stages in life to achieve successful aging. Erikson (1963) described the primary task of old age as being able to see one’s life as having been lived with integrity. In the absence of achieving that sense of having lived well, the older adult is at risk for becoming preoccupied with feelings of regret or despair. Stages of psychological development o Infant - Trust vs Mistrust o Toddler - Autonomy vs Shame & Doubt o Pre-Schooler - Initiative vs Guilt o Schooler - Industry vs Inferiority o Teenager - Identity vs Role confusion o Young Adult - Intimacy vs Isolation o Middle-age Adult - Generativity vs Stagnation o Older Adult - Integrity vs Despair 3. Disengagement Theory Refers to an inevitable process in which many of the relationships between a person and other members of society are severed. As older adults slow down, they gradually withdraw from the society. Disengagement is a mutual activity in which the elderly not only disengaged in the society, but the society disengages from the older adult. According to this theory, this withdrawal process is predictable,systemic, inevitable, and necessary for proper functioning of a growing society. The benefit to society is thought to be an orderly transfer of power from old to young. The elderly develops greater self-preoccupation and decrease emotional ties with people and reduced interest in social activities. Such social withdrawal and increased self-absorption were thought to increase life satisfaction among them.  This theory formulated by Cummings and Henry states that aging people withdraw from customary roles and engage in more introspective, self-focused activities. This theory includes 4 basic concepts:  Aging person and society mutually withdraw from each other.  Disengagement is biologically and psychologically intrinsic and inevitable.  Disengagement is considered necessary for successful aging.  Disengagement is beneficial for older adults and society 4. Activity Theory As opposed to the disengagement theory, this theory argues that the more active and involved the elderly are, the more likely that they are satisfied with their lives. This theory occurs when individuals engage in a full day of activities and maintain a level of productivity to age successfully.It says , the more you do , the better you will age.People who remain active and engaged tend to be happier , healthier , and more in touch with what is going on around them. Activity theory emphasizes the importance of ongoing social activity. This theory suggests that a person's self-concept is related to the roles held by that person. Successful aging and life satisfaction depend on maintaining high level of activity. According to this perspective, the maintenance of optimal physical, mental and social activity is necessary for successful aging this theory also assumes that older adults have the same needs as middle-age persons. It is therefore important to find substitute activities for them after their retirement. 5. Continuity theory Also called developmental theory. This theory is the follow up to the disengagement and activity theories. It emphasizes the individual previously established coping abilities and personal character traits as a basis for predicting how the person will adjust to changes of aging.  The continuity or developmental theory states that personality remains the same and behaviour become more predictable as people age. This theory focuses more personality and individual behaviour over time. In later life, adults tend to use continuity as an adaptive strategy to deal with changes that occur during normal aging. Older adults tend to maintain the same relationships and activities as they did when they were young.  Few other theories 1. Programmed Cellular Aging Theory: Suggest that aging may be result of an impairment of the cells in translating necessary RNAs as a result of increased turnoffs of DNA. In other words, the transcription of these messages into functional protein may be restricted in older people. Some segments of DNA become depleted with advancing age, or selected cellular structures seem to change with so that DNA transcription is restricted. 2. Glycation theory Glycation is the nonenzymic reaction between glucose & tissue protein. The negative effects of this process on proteins may be a major contributor to age changes. 3. DNA Damage Theories: Aging is caused by accumulated damage to DNA, which in turn inhibits cells ability to function and express the appropriate genes. This led to cell death and overall aging of the organism 4. Autoimmune Theory According to this, as the age advances, there is faltering in the process of protein synthesis, resulting in the production of a new protein, which is not accepted by the body resulting in the production of antibodies against it, which is the basis of senescence. As the body ages the immune system is less able to deal with foreign organisms & increasingly make mistakes by identifying one’s own tissues as foreign. According to this theory the immune system is responsible for aging. An aging immune system is less able to distinguish body cells from foreign cells; as a result, it begins to attack and destroy body cells as if they were foreign. Erratic cellular mechanisms are thought to attack on body tissues through auto aggression or immune-defence. 5. Error & fidelity theory Error theory focus on the phenomenon of decreased bonding of protein cells that occurs spontaneously or in response to stressors such as radiation. This stressor results in errors in the synthesis of RNA and DNA and produces cells with impaired function. 6. Psychosocial Theories of Aging: Psychosocial theories of aging attempt to explain age – related changes in cognitive function, such as intelligence, memory, learning and problem – solving 7. Exchange theory The exchange theory simply states that people should end the relationship with another person if nothing can be gained or exchanged from that person. 8. Jung’s theory As individuals age, they go through a re-evaluation stage at midlife then they begin to question whether the decisions and the choices they have made were the right choices for them 9. Adjustment Theory: Adjustment theory defines aging as a series of adjustment to retirement, to grandparenthood, to change in income, to changes in social life and marital status and to potential deterioration of health and well-being. 10. Social Exchange Theory Postulates that social interactions between individuals and groups continues as long as everyone profits from the interaction. 11. Social Breakdown -Reconstruction Theory This theory states that aging is promoted through negative psychological functioning brought about by the negative views of the society about elderly and inadequate provision of services for them.  Social reconstruction can occur by changing the society’s view of the elderly and by providing adequate social services for them.