From the Chicago MeetingsThe biology of aging☆,☆☆,★
Section snippets
What is aging?
Aging has been defined concisely by Miller1 as “a process that converts healthy adults into frail ones, with diminished reserves in most physiological systems and an exponentially increasing vulnerability to most diseases and to death.”
This definition incorporates several important concepts regarding physiologic aging. First, aging deals with the changes that take place between middle age and old age, as opposed to the physiologic changes that take place early in life during maturation. Second,
How do we age?
The biologic theories of how we age can be divided into two major categories—the “programmed”2 and “wear-and-tear”3 theories (Table I).The first category looks at aging as the result of genetic events. The programmed theories view aging as the result of an innate genetic program. This program determines the rate of aging and maximal lifespan. This view predicts the existence of a primary clock (or clocks) that times the aging process.4 In support of this, when rodent lifespan is extended by
The “programmed” theories of aging
There is much evidence that aging has a strong genetic component (Table II).• The lifespan of a given species is relatively fixed. • Human aging has a significant genetic component. • Single mutations in human beings can produce premature aging syndromes. • Altered expression of a single gene may increase maximal lifespan in lower organisms.
The “wear and tear” theories of aging
There is strong experimental evidence that wear and tear play an important role in the aging process (Table III).The production of free radicals and free radical damage increases with age.13 Longer-lived species are less susceptible to oxidative stress than shorter-lived species. Fruit flies genetically engineered to have high antioxidant defenses live longer.14 The concept that random damage to important cellular components could account for what we call “the aging process” has been around for
A unified theory of aging
Any unified theory of aging has to account for as many of the observations of “how” we age as possible. At the present time, the general form of the free radical theory does this the best. In addition, the genetic component of the aging process must be accounted for.21 Fig 1 presents a possible unified theory. The body continually undergoes oxidative damage from free radicals generated by cellular metabolism and by environmental sources. However, the body also contains elaborate mechanisms to
Why we age: An evolutionary perspective
Until now, we have been discussing the question of how we age—that is, what are the biologic mechanisms by which we develop an increasing vulnerability to diseases and death? We now turn to the question of why we age. This question can be answered from a biologic perspective in terms of evolutionary considerations. However, it should be noted that evolution works to maximize the fitness of individuals. It does not increase fitness at the species level. Therefore it does not maximize the fitness
Why we age: A philosophic perspective
As noted in the introduction, one can also address the question of why we age from a philosophic/spiritual perspective. With regard to human aging, it is amazing that we now enjoy a long period of time between the cessation of reproduction and the end of life. In women, reproduction ends at about age 50, but the average age of death is in the early 80s. As lifespan continues to increase as a result of medical advances, this post-reproductive period will continue to grow longer. The question may
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Pathomolecular effects of homocysteine on the aging process: A new theory of aging
2007, Medical HypothesesAging
2019, Encyclopedia of Gastroenterology, Second EditionAlcohol and Opioid Use Disorder in Older Adults: Neglected and Treatable Illnesses
2016, Current Psychiatry ReportsNatural plant polyphenols for alleviating oxidative damage in man: Current status and future perspectives
2016, Tropical Journal of Pharmaceutical ResearchAgeing: Consequences of excessive free radicals and inflammation
2016, Current ScienceEffect of successful aging on mortality in older individuals: The PALA study
2014, Dementia e Neuropsychologia
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Supported by the St Louis Geriatric Research, Education and Clinical Center; by the Medical Research Service of the Department of Veterans Affairs; and by National Institutes of Health Grant AG-12587.
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Reprint requests: H. J. Armbrecht, PhD, Geriatric Center (11G-JB), St Louis VA Medical Center, St Louis, MO 63125.
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