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Controversy2SP181.pptxControversy 2
Why Do Our Bodies Grow Old?
Why Do Our Bodies Grow Old?
Moody, Aging 9e. SAGE Publishing, 2018.
The maximum lifespan for the human species appears to be around 120 years
We have no valid records of people living much beyond 120 years
Over recent years, life expectancy (e.g., average number of years lived) has risen; but lifespan (e.g., maximum possible length of life) hasn’t changed at all
How long are you going to live? (6:55)
127-year-old women is the world’s oldest living person (0:52)
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Why Do Our Bodies Grow Old? (cont.)
Moody, Aging 9e. SAGE Publishing, 2018.
Compression of Morbidity theory: suggests we should aim for a healthy old age, followed by a rapid decline and death, which would likely:
Enhance the quality of life
Extend life expectancy and “health span”
Reduce health care costs and caregiver burden
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The Process of Biological Aging
Moody, Aging 9e. SAGE Publishing, 2018.
Senescence (Normal Biological Aging): an underlying time-dependent biological process that, although not itself a disease, involves functional loss and susceptibility to disease and death.
Gompertz Law—death rates for contemporary humans double every 8 years (ex., a 38-year-old would be twice as likely to die as a 30-year-old)
Additionally, at any given age, men are twice as likely to die as women
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The Process of Biological Aging (cont.)
Moody, Aging 9e. SAGE Publishing, 2018.
Comparative Anatomy—the study of the structure of different species
Helps us understand differences in aging and lifespan across species
The rate of aging can be correlated with the amount of time it takes the death rate of a species to double
e.g., the doubling time for humans is 8 years, but it is 10 days for a fruit fly and 3 months for a mouse
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The Process of Biological Aging (cont.)
Moody, Aging 9e. SAGE Publishing, 2018.
Rate-of-Living Concept—the concept that metabolism and life expectancy are closely related
Smaller organisms, which have faster metabolisms, also have shorter life expectancies
Human beings have an average lifespan and maximum life expectancy about twice as great as those of any other primate
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Biological Theories of Aging
Moody, Aging 9e. SAGE Publishing, 2018.
No single theory of aging explains all the complex processes that occur in cells and body systems
But ongoing research is finding new insights into why we grow old
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Biological Theories of Aging (cont.)
Moody, Aging 9e. SAGE Publishing, 2018.
Two basic kinds of theory of aging:
Chance—the result of external events
Fate—the result of an internal necessity
The question remains whether or not it’s possible to intervene to correct damage to the aging body or modify the genetic program
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Biological Theories of Aging (cont.)
Moody, Aging 9e. SAGE Publishing, 2018.
Wear-and-Tear theory—sees aging as the result of chance
A good explanation for some aspects of aging, such as the fact that our joints and bones become damaged over time as an outcome of living
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Biological Theories of Aging (cont.)
Moody, Aging 9e. SAGE Publishing, 2018.
Somatic Mutation theory—notes that cells can be damaged by radiation, and as a result, mutate or experience genetic changes
A more modern and sophisticated version of the wear-and-tear theory, but little science evidence to support it at this point
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Biological Theories of Aging (cont.)
Moody, Aging 9e. SAGE Publishing, 2018.
Error Accumulation theory (aka error catastrophe theory)—posits that decremental changes of senescence are the result of chance or random changes that downgrade the genetic code
Over time, small errors in genetic coding occur and eventually make the later copies unreadable (e.g., like using a photocopy to make another copy)
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Biological Theories of Aging (cont.)
Moody, Aging 9e. SAGE Publishing, 2018.
Accumulative Waste theory—suggests that the accumulation of waste products eventually interferes with cell metabolism and leads to death
According to scientific research, although waste products do accumulate, there is little evidence of harm to the organism
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Biological Theories of Aging (cont.)
Moody, Aging 9e. SAGE Publishing, 2018.
Autoimmune theory—the system may eventually become defective and no longer distinguish the body’s own tissues from foreign tissues
The body may then begin to attack itself, as suggested by the increase with age in autoimmune diseases, such as rheumatoid arthritis, that result from inflammatory processes
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Biological Theories of Aging (cont.)
Moody, Aging 9e. SAGE Publishing, 2018.
Aging-Clock theory—claims that aging is programmed into our bodies like a clock ticking away from conception
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Biological Theories of Aging (cont.)
Moody, Aging 9e. SAGE Publishing, 2018.
Cross-Linkage Theory—claims that the bodily changes that we see as we age result from the accumulation of cross-linking compounds in the collagen, which gradually becomes stiff
Collagen—a natural protein found in the skin, bones, and tendons
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Biological Theories of Aging (cont.)
Moody, Aging 9e. SAGE Publishing, 2018.
Free Radicals—damage created by free radicals (molecules that appear as a byproduct of oxygen metabolism in cells) eventually gives rise to the biological changes associated with aging
The body produces anti-oxidants—substances that protect against free radicals that prevent damage to cells
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Biological Theories of Aging (cont.)
Moody, Aging 9e. SAGE Publishing, 2018.
Cellular Theory—argues that aging ultimately results from the progressive weakening of capacity for cell division, perhaps through exhaustion of the genetic material
Hayflick limit—the finite number of cell divisions that normal human cells in tissue culture go through
Named after discoverer Leonard Hayflick (1961)
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Is Aging Inevitable?
Moody, Aging 9e. SAGE Publishing, 2018.
The biological aging process may not be the result of a rigid genetic program:
It may simply be the complex and indirect result of multiple traits in the organism tied to normal development
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Is Aging Inevitable? (cont.)
Moody, Aging 9e. SAGE Publishing, 2018.
But aging is not a disease
Rather, it’s a normal process of change, part of which may make us more vulnerable to disease
And the process is life-long, beginning the moment we are born
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Environmental and Genetic Approaches
Moody, Aging 9e. SAGE Publishing, 2018.
There is only one environmental intervention that has scientifically been shown to be connected to longevity in mammals: restricting food intake
When caloric intake is reduced—by up to 40% fewer calories than normal—aging-related deterioration slows down, and aging-related diseases are diminished
This is possibly because caloric reduction slows metabolism—the rate at which food is transformed into energy
For any individual, length of life will be the result of both genetic and environmental factors
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Compression or Prolongation of Morbidity?
Moody, Aging 9e. SAGE Publishing, 2018.
Various environmental and genetic alterations have been shown to increase lifespan among simple organisms
But human beings are more complex, and there is still no conclusive evidence from research on humans
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Compression or Prolongation of Morbidity? (cont.)
Moody, Aging 9e. SAGE Publishing, 2018.
According to the book, the compression of morbidity theory stands out as an important reminder of how critical biological research will be for the future of an aging society
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Reading 5: Why Do We Live as Long as We Do?
Moody, Aging 9e. SAGE Publishing, 2018.
Discuss Hayflick's basic premise regarding the increase in longevity of the human species. What are the key aspects—and implications—of his premise?
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Reading 6: Vitality and Aging
Moody, Aging 9e. SAGE Publishing, 2018.
Fries and Crapo, writing in the 1980s, provided a “new syllogism” about human aging. What are the key components of their model of biophysical aging? Is there any indication that what they propose in their model has been borne out in the past two decades as more people reach later life and research on biological aging has expanded?
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Reading 7: The Compression of Morbidity Hypothesis
Moody, Aging 9e. SAGE Publishing, 2018.
What are the key components of the “compression of morbidity hypothesis”? While author Mor agrees that there have been improvements in the rate of late life morbidity, he questions whether this trend will continue into the future. What are some of the reasons for his concern?
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Reading 8: Health Trends in the Older Adult Population
Moody, Aging 9e. SAGE Publishing, 2018.
Parker and Thorslund assert that “a concept of general morbidity is not sufficient when discussing health trends and the need for care services in the elderly population.”
What do they propose as an alternative?
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Reading 9: We Will Be Able to Live to 1,000
Moody, Aging 9e. SAGE Publishing, 2018.
If Aubrey de Grey’s proposal for curing aging were to come to pass, what would aging and later life look like? What would society look like?
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Reading 10: Don’t Fall for the Cult of Immortality
Moody, Aging 9e. SAGE Publishing, 2018.
Olshansky provides a counter argument to de Grey’s agenda to “cure aging.”
What are the key ideas in Olshansky’s argument? Taken together, which side of the debate do you find to be more compelling? More realistic?
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