Biogerontology
Biogerontology is the sub-field of gerontology concerned with the biological aging process, its evolutionary origins, and potential means to intervene in the process. The term "biogerontology" was coined by S. Rattan, and came in regular use with the start of the journal BIOGERONTOLOGY in 2000. It involves interdisciplinary research on the causes, effects, and mechanisms of biological aging. Biogerontologist Leonard Hayflick has said that the natural average lifespan for a human is around 92 years and, if humans do not invent new approaches to treat aging, they will be stuck with this lifespan.[1] James Vaupel has predicted that life expectancy in industrialized countries will reach 100 for children born after the year 2000.[2] Many surveyed biogerontologists have predicted life expectancies of more than three centuries for people born after the year 2100.[3] Other scientists, more controversially, suggest the possibility of unlimited lifespans for those currently living. For example, Aubrey de Grey offers the "tentative timeframe" that with adequate funding of research to develop interventions in aging such as strategies for engineered negligible senescence, "we have a 50/50 chance of developing technology within about 25 to 30 years from now that will, under reasonable assumptions about the rate of subsequent improvements in that technology, allow us to stop people from dying of aging at any age".[4] The idea of this approach is to use presently available technology to extend lifespans of currently living humans long enough for future technological progress to resolve any remaining aging-related issues. This concept has been referred to as longevity escape velocity.
Approaches to aging
Biogerontologists vary in the degree to which they focus on the study of the aging process as a means of mitigating the diseases of aging, or as a method for extending lifespan. A relatively new interdisciplinary field called geroscience focuses on preventing diseases of aging and prolonging the 'healthspan' over which an individual lives without serious illness.[5][6][7] The approach of biogerontologists is that aging is disease per se and should be treated directly, with the ultimate goal of having the probability of individual dying be independent of their age (if external factors are held constant).[8][9][10] This is in contrast to the opinion that maximum life span can not, or should not, be altered.
Biogerontology should not be confused with geriatrics, which is a field of medicine that studying the treatment of existing disease in aging people, rather than the treatment of aging itself.
There are numerous theories of aging, and no one theory has been entirely accepted. At their extremes, the wide spectrum of aging theories can be categorized into programmed theories – which imply that aging follows a biological timetable, and error theories – which suggest aging occurs due to cumulative damage experienced by organisms.[11]
Stochastic theories
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. The notion of accumulated damage was first introduced in 1882 by biologist Dr. August Weismann as the "wear and tear" theory.[12][13]
Wear and tear theories
Wear and tear theories of aging began to be introduced yet in 19th century.[13] They suggest that as an individual ages, body parts such as cells and organs wear out from continued use. Wearing of the body can be attributable to internal or external causes that eventually lead to an accumulation of insults which surpasses the capacity for repair. Due to these internal and external insults, cells lose their ability to regenerate, which ultimately leads to mechanical and chemical exhaustion. Some insults include chemicals in the air, food, or smoke. Other insults may be things such as viruses, trauma, free radicals, cross-linking, and high body temperature.[14]
Accumulation
Accumulation theories of aging suggest that aging is bodily decline that results from an accumulation of elements, whether introduced to the body from the environment or resulting from cell metabolism.[14]
Mutation accumulation theory
Mutation accumulation theory was first proposed by Peter Medawar in 1952[12] as an evolutionary explanation for biological ageing and the associated decline in fitness that accompanies it.[15] The theory explains that, in the case where harmful mutations are only expressed later in life, when reproduction has ceased and future survival is increasingly unlikely, then these mutations are likely to be unknowingly passed on to future generations.[16] In this situation the force of natural selection will be weak, and so insufficient to consistently eliminate these mutations. Medawar posited that over time these mutations would accumulate due to genetic drift and lead to the evolution of what is now referred to as ageing.
Free radical theory
DNA damage theories
DNA damage is distinctly different from
Cross-linking theory
The cross-linking theory proposes that
Stem cell theory of aging
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Genetic
Genetic theories of aging propose that aging is programmed within each individual's genes. According to this theory, genes dictate cellular longevity. Programmed cell death, or apoptosis, is determined by a "biological clock" via genetic information in the nucleus of the cell. Genes responsible for apoptosis provide an explanation for cell death, but are less applicable to death of an entire organism. An increase in cellular apoptosis may correlate to aging, but is not a 'cause of death'. Environmental factors and genetic mutations can influence gene expression and accelerate aging.
More recently epigenetics have been explored as a contributing factor. The epigenetic clock, which relatively objectively measures the biological age of cells, are useful tool for testing different anti-aging approaches.[33] The most famous epigenetic clock is Horvath's clock, but now already more accurate analogues have appeared.
General imbalance
General imbalance theories of aging suggest that body systems, such as the endocrine, nervous, and immune systems, gradually decline and ultimately fail to function. The rate of failure varies system by system.[14]
Immunological theory
The immunological theory of aging suggests that the immune system weakens as an organism ages. This makes the organism unable to fight infections and less able to destroy old and
See also
- Antagonistic pleiotropy hypothesis
- Hallmarks of aging
- Biomarkers of aging
- Aging and memory
- Old age
- Research into centenarians
- Longevity escape velocity
- List of life extension topics
- Timeline of senescence research
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- ^ Fabian, Daniel (2011). "The Evolution of Aging". Nature Education Knowledge. 3: 1–10.
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attribution contains material copied from Gerontology.