Definition of biological aging

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Definition of biological aging

• Primary aging
• gradual, inevitable, universal changes
• Secondary aging
• processes that affect the rate at which primary
  aging occurs

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Theories of aging

• Evolutionary theories
• Mutation accumulation
• Antagonistic pleiotropy
• Molecular theories
• Gene regulation
• Error catastrophe
• Cellular theories
• Wear and tear
• Free radial
• System theories
• Neuroendocrine
• Immunologic

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Why do we live as long as we do?

• Aging past the reproductive years is a paradox in
  evolutionary terms
• How can natural selection favour a long
  post-reproductive life span?
• How can genes good for healthy ageing be selected
  and genes bad for it be eliminated?

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Mutation accumulation

• Natural selection is negligent of events that
  occur in later life. Thus deleterious mutations
  are not eliminated and can accumulate. Together
  they cause ageing and death.

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Antagonistic pleiotropy

• Genes exist that affect multiple traits in
  opposite ways. Natural selection should favor
  those pleiotropic genes that maximize vigor in
  youth, even though at the expense of vigor in
  later life.

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Long post-reproductive life a selected trait?

• Long-living and healthy grandmothers may ensure
  the propagation of their own gene pool by
  ensuring the survival of their grandchildren and
  enabling their daughters to have more children.

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Time devoted to food acquisition (Hawkes et al.
1997)
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Patterns of covariation
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Wear-and-tear

• Processes essential to survival produce
  cumulative injury and damage that over time lead
  to disability and death.

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Free radical theory

• Free radicals, formed naturally within the cell
  during aerobic metabolism, will bind with any
  molecular structure in the cell and cause
• Breakdown of cellular processes
• Interference with gene expressions
• Accumulation of inert substances
• Alteration of membrane characteristics

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The evidence

• Supporting evidence
• greater FR production in short-lived species
• superoxide dismutase (SOD) levels vary with
  longevity and age
• animals given antioxidants live longer
• BUT
• problems with animal experiments
• does free radical neutralization suppress disease
  or prolong life?

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Antioxidant effects in humans

• Suppose you find a positive relationship between
  vitamin E intake and functional measures (e.g.
  cognition, activity). How do you interpret this
  relationship?

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Mortality by cause and sex, Canada 2001
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Sensory efficiency activity a model
Yesterday
ADL
Hearing
-.59
.23
Expanded competence
Basic competence
.17
Age
.68
-.78
.42
Vision