Theories of Aging PDF

Theories of aging There are many theories about the mechanisms of age related changes. No one theory is sufficiently able to explain the process of aging, and they often contradict one another. All valid theories of aging must meet three broad criteria:  The aging changes that the theory addresse...

Theories of aging There are many theories about the mechanisms of age related changes. No one theory is sufficiently able to explain the process of aging, and they often contradict one another. All valid theories of aging must meet three broad criteria:  The aging changes that the theory addresses must occur commonly in all members of a humans.  The process must be progressive with time. That is, the changes that result from the proposed process must become more obvious as the person grows older.  The process must produce changes that cause organ dysfunctions and that ultimately cause a particular body organ or system to fail. Modern biological theories 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 and defense responses), and the damage or error theories emphasize environmental assaults to living organisms that induce cumulative damage at various levels as the cause of ageing. A -The programmed theory: 1) Aging by Program( biological clock theory). 2) Gene Theory, 3) Autoimmune Theory B -The damage or error theory: 1) Wear and tear theory 2) Free radicals theory 3) Cross-linkage theory Programmed theory/ 1) Biological clock theory: 1. According to this theory aging and death are natural and necessary part of genetics. The human are programmed to age and die. 2. The program theory proposes that every person has a “Biologic clock” that starts ticking at the time of conception. 3. In this theory each individual has a genetic program specifying an unknown but predetermined number of cell division. 4. As the program plays out, the person experiences predictable changes such as atrophy og the thymus, menopause and skin changes and graying of the hair. Aging has a biological timetable or internal biological clock. 2) Gene theory 1. The gene theory proposes the existence of one or more harmful genes that activate overtime, resulting in the typical changes see with aging and limiting life span of the individual. 2. Organism failure in the later life because of the presence of imperfect genes activated over lengthy periods of time. 3. Two gene types, one supports growth and vigor, and the other supports sentence and deterioration. 3) Auto immune theory: Postulates that with age, immune system produces auto anti-bodies that causes cell death or changes that foster the aging process. 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. B -The damage or error theory: 1) Wear and tear theory: Years of damage to cells, tissue and organs eventually wears them out. where vital parts in our cells and tissues wear out resulting in ageing 2) The free radical theory: 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. Ex of free radicals: Diet, lifestyle, drugs (e.g. tobacco and alcohol) and radiation. During aging, damage produced by free radicals cause cells and organs to stop functioning, molecules that are damaged by free radicals are proteins and DNA. This theory proposes that superoxide and other free radicals cause damage to the macromolecular components of the cell, giving rise to accumulated damage causing cells, and eventually organs, to stop functioning. 3) Cross linkage theory or connectivity theory: Also known as collagen theory. With age, protein, DNA and other structured molecules develop inappropriate cross links to one another which decreases the elasticity of protein and other molecules. Damage and unneeded protein stick around and can cause problem. Cell molecules from DNA and connective tissue interact with free radicals to cause bonds that decrease the ability of tissue to replace it. The results in the skin changes typically attributed to aging such as dryness, wrinkles, and loss of elasticity. loosening teeth, diminished elasticity of arterial walls and decreased efficiency of lungs and GI tract.  Social theories of aging Disengagement theory Activity theory Continuity theory Age stratification theory Social exchange theory Modernization theory Disengagement theory As individuals age, they withdraw from society and society encourages this withdrawal. Individuals would change from being centered on society and interacting in the community to being self-centered persons withdrawing from society Social equilibrium would be the end result Activity theory In contrast to Disengagement Theory, Activity Theory, suggests that staying active and maintaining social interactions leads to greater satisfaction in old age. The theory posits that continued engagement in activities and social roles contributes to a higher quality of life and well-being for older adults. Continuity theory This theory emphasizes the importance of maintaining continuity in roles, relationships, and activities that are important to an individual's sense of self. Inclined to maintain habits. Personalities and lifestyle.  Age Stratification Theory this theory posits that society is structured by age, with different age groups having varying roles, rights, and responsibilities. The theory examines how different cohorts experience aging and how society organizes itself around age-related expectations and norms. Age stratification highlights the role of social institutions in shaping the aging process and how societal changes impact different generations. Social exchange theory This theory suggests that social interactions are based on a system of rewards and costs. As individuals age, they may experience a decrease in resources (such as health, income, or social status), which can affect their social exchanges and relationships. Older adults might face social marginalization if they are perceived as offering fewer resources or rewards in social interactions. Modernization theory Modernization Theory posits that the status of older adults declines as societies become more modernized. In pre-industrial societies, elders were often respected for their knowledge and experience, but industrialization and modernization have led to a decline in their social status, as younger generations acquire the skills and knowledge needed for success in a modern economy.