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Oxidative free radicals, such as the hydroxyl radical and the superoxide radical, can cause DNA damages, and such damages have been proposed to play a key role in the aging of crucial tissues. [20] DNA damage can result in reduced gene expression, cell death and ultimately tissue dysfunction. [20]
Stochastic theories of aging are theories suggesting that aging is caused by small changes in the body over time and the body's failure to restore the system and mend the damages to the body. Cells and tissues are injured due to the accumulation of damage over time resulting in the diminished functioning of organs.
Aging is characterized by a progressive loss of physiological integrity, leading to impaired function and increased vulnerability to death. The hallmarks of aging are the types of biochemical changes that occur in all organisms that experience biological aging and lead to a progressive loss of physiological integrity, impaired function and, eventually, death.
Senescence (/ s ɪ ˈ n ɛ s ə n s /) or biological aging is the gradual deterioration of functional characteristics in living organisms. Whole organism senescence involves an increase in death rates or a decrease in fecundity with increasing age, at least in the later part of an organism's life cycle.
Degenerative disease is the result of a continuous process based on degenerative cell changes, affecting tissues or organs, which will increasingly deteriorate over time. [1] In neurodegenerative diseases, cells of the central nervous system stop working or die via neurodegeneration. An example of this is Alzheimer's disease. [2]
Progeria is another example of a disease that may be related to cell senescence. The disease is thought to be caused by mutations in the DNA damage response, telomere shortening, or a combination of the two. [82] Progeroid syndromes are all examples of aging diseases where cell senescence appears to be implicated.
A related theory is that mutation, as distinct from DNA damage, is the primary cause of aging. A comparison of somatic mutation rate across several mammal species found that the total number of accumulated mutations at the end of lifespan was roughly equal across a broad range of lifespans. [ 49 ]
More recently, biomarkers of aging has been used in multiple clinical trials to measure slowing or reversing of age-related decline or biological aging. [19] The Biomarkers of Aging Consortium (https://www.agingconsortium.org) is currently examining the application of these biomarkers to identify longevity interventions and ways to validate ...