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Aging Theories
| Theory of Aging | Type | Definition | Additional Info |
|---|---|---|---|
| Free radical theory | Biological | Free radicals damage cell membranes/DNA replication; interfere with cell diffusion/transport; may cause pathologic changes | free radicals are highly reactive/toxic forms of O2 produced by cell mitochondria |
| Cell mutation | Biological | errors in protein (DNA/RNA) synthesis lead to abnormal proteins and aging changes | aka intrinsic mutagenesis |
| Hormonal theory | Biological | decrease in neurons & associated hormones leads to aging changes | decrease in protective hormones/increase in stress hormones |
| Immunity theory | Biological | Steady decrease in immune responses throughout adulthood | thymus size & bone marrow cell efficiency both decrease |
| Environmental toxin (aka stochastic/non-genetic theory) | Environmental | Aging caused by accumulated toxins from environment (ultraviolet, cross-linking agents, toxic chemicals, radiation, viruses) | Can result in errors in protein synthesis, DNA synthesis and genetic sequences, cross-linkage of molecules, mutations |
| Stress Theory | Psychological | imbalances in homeostasis lead to changes in chemical and structural composition | linked to hormonal theory |
| Erickson's Bipolar Theory of Lifespan Development | Psychological | individual either views life with satisfaction, optimism, growth or with fear of death, regret, and disappointment | Integrity v. despair |
| Activity theory | Sociological (life experiences/lifestyles influence aging) | older adults who are socially active adjust better to aging | allows for continuation of roles that promote positive self-image/satisfaction |
| Disengagement theory | Sociological | individual distances him/herself or withdraws from society | decrease in social roles leads to further isolation and dissatisfaction |
| Dependency | Sociological | increased reliance on others for physical and emotional needs | increased focus on self |
| Integrated Model | Integrated | aging is a complex, multifactorial phenomenon affected by some or all of the factors described in other theories | Aging is not adequately explained by one theory |
| Genetic | Biological | Aging is intrinsic to organism. Genes are programmed to modulate aging changes & rate of progression. | Individuals vary in the expression of aging |
| Doubling/biologic clock | Biological | cellular deterioration due to limits of cell replication | aka Hayflick limit theory |