Life extension science, also known as anti-aging medicine, indefinite life extension, experimental gerontology, and biomedical gerontology, is the study of slowing down or reversing the processes of aging to extend both the maximum and average lifespan. Some researchers in this area, and "life extensionists" or "longevists" (those who wish to achieve longer lives themselves), believe that future breakthroughs in tissue rejuvenation with stem cells, molecular repair, and organ replacement (such as with artificial organs or xenotransplantations) will eventually enable humans to have indefinite lifespans (agerasia[1]) through complete rejuvenation to a healthy youthful condition.
The sale of putative anti-aging products such as nutrition, physical fitness, skin care, hormone replacements, vitamins, supplements and herbs is a lucrative global industry, with the US market generating about $50billion of revenue each year.[2] Some medical experts state that the use of such products has not been proven to affect the aging process, and many claims of anti-aging medicine advocates have been roundly criticized by medical experts, including the American Medical Association.[2][3][4][5][6]
However, it has not been shown that the goal of indefinite human lifespans itself is necessarily unfeasible; some animals such as lobsters and certain jellyfish do not die of old age, and an award was offered to anyone who could prove life extensionist Aubrey de Grey's hopes were 'unworthy of learned debate'; nobody won the prize.[7] The ethical ramifications of life extension are debated by bioethicists.
Life extension is a controversial topic; many people oppose it due to fear of overpopulation and effects on society. Religious people are no more likely to oppose life extension than the unaffiliated,[8] though some variation exists between religious denominations. Blacks and Hispanics are more likely to support life extension than white people.[8] Biogerontologist Aubrey De Grey counters the overpopulation critique by pointing out that the therapy could postpone or eliminate menopause, allowing women to space out their pregnancies over more years and thus decreasing the yearly population growth rate.[9]
A Spring 2013 Pew Research poll in the United States found that 38% of Americans would want life extension treatments, and 56% would reject it. However it also found that 68% believed most people would want it and that only 4 percent consider an "ideal lifespan" to be more than 120 years.[8]
During the process of aging, an organism accumulates damage to macromolecules, its cells, its tissues and its organs. This accumulated damage is the result of oxidation damage to the cell contents caused by free radicals,[10][11] though other things cause aging as well.
The longest a human has ever been proven to live is 122 years, the case of Jeanne Calment who was born in 1875 and died in 1997, whereas the maximum lifespan of a mouse, commonly used as a model in research on aging, is about four years. Genetic differences between humans and mice that may account for these different aging rates include differences in efficiency of DNA repair, types and quantities of antioxidant enzymes, rates of free radical production and rates of occurrence of DNA damage. Another challenging factor is the telomere limitation of each individual species.
Average lifespan in a population is lowered by infant and child mortality, which are frequently linked to infectious diseases or nutrition problems. Later in life, vulnerability to accidents and age-related chronic disease such as cancer or cardiovascular disease play an increasing role in mortality. Extension of expected lifespan can often be achieved by access to improved medical care, vaccinations, good diet, exercise and avoidance of hazards such as smoking.
Maximum lifespan is determined by the rate of aging for a species inherent in its genes and by environmental factors. One widely recognized method of extending maximum lifespan in organisms such as nematodes and mice is caloric restriction. Another technique used evolutionary pressure such as breeding from only older members.
Theoretically, extension of maximum lifespan could be achieved by reducing the rate of aging damage, by periodic replacement of damaged tissues, or by molecular repair or rejuvenation of deteriorated cells and tissues and the enhancement of telomerase enzyme activity. Future research will be geared towards telomere repair strategies.
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