gerontological nursing

1. Biological Theories Of
aging
Under Supervision Of
Assist Prof Dr. Nadia Hassan
Prepared by
De. Doaa Mohamed Zein Elabdeen
2019/2020

3. outlines Introduction
Definition of
theories of
aging
Definition of
biological
theory
Criteria of
valid theories
of aging
Biological
theories
concerned
classification
of Modern
Aging Theories
Empirical
Evidence
Supporting
Implications
for Medicine
Anti-Aging
Behaviors Conclusion References

4. introduction
Aging is an irreversible, time-
dependent, functional decline
that converts healthy adults into frail
ones, with reduced capacity to adjust to
everyday stresses, and increasing
vulnerability to most diseases, and to
death. As far as anyone knows, the
longest anyone has ever lived is 121 yr.
The record-holder is Jeanne Calment, a
French lady who celebrated her
landmark birthday in 1996. Long lives
always make us wonder: What is the
secret behind it? Is there a
maximum lifespan beyond which we
cannot live?

5. What happens as we age? Would insight into longevity help us fight
the diseases and disabilities associated with the aging process?. As a
result, a myriad of theories explaining the aging phenomenon have
been proposed, which can be grouped into two major categories. The
first includes the programmed theories, which emphasize internal
biological clocks or programs. The second includes the wear-and-tear
theories, which emphasize the role of wear and tear caused by random
events over time

6. Definition of theories of Aging:
Attempt to explain the phenomenon of
aging as it occurs over the life span.
Criteria of valid theories of aging
There are many theories about the
mechanisms of age-related
changes. No one theory is sufficiently
able to explain the process of aging,
and they often contradict one
another. All valid theories of aging
must meet three broad criteria

7. -The aging changes that the theory addresses must occur
commonly in all members of a humans.
-The process must be progressive with time. That is, the
changes that result from the proposed process must become
more obvious as the person grows older.
-The process must produce changes that cause organ
dysfunctions and that ultimately cause a particular body organ
or system to fail.

9. Definition of Biological
theories
it concerned with the
physiological
processes that occur in
all living organisms as
they chronologically
age.
Biological theories
concerned with
• Deleterious effects leading to
decreasing function of the organism
• Gradually occurring age-related
changes that are progressive over time
• Intrinsic changes that can affect all
member of a species because of
chronologic age

10. classification of Modern
Aging Theories
Modern evolutionary aging theories followed by
most medical researchers fall into two categories:
Modern programmed aging
theories
Modern non-
programmed aging
theories

11. Modern Non-Programmed Aging Theories:-
also known as non-adaptive or passive theories, contend
that aging doesn't serve a valid "selectable" evolutionary
purpose and that therefore an evolved mechanism whose
primary purpose is to cause aging or otherwise purposely
limit life span can not exist, at least not in mammals. These
theories contend that aging is an unavoidable adverse side-
effect of some useful biological function

12. contend that organisms are designed to have a
genetically programmed limited life span
because aging and consequently limited life span
serves some evolutionary purpose. According to
this concept,
Programmed theories
also known as adaptive or
active theories

13.  aging is a necessary biological function, and
like other biological functions can be directed
by a complex life span regulation system
involving hormones, signaling, genes, sensing
of external conditions, and other
characteristics typical of evolved biological
functions. A life span longer than some
species-specific value conveys disadvantage
and therefore produced evolutionary
motivation to develop the aging function or
other means for purposely limiting life span.

14. I. Programmed
Theory

15. i. Programmed Longevity: -
Aging is the result of a sequential
switching on and off certain genes,
with senescence being defined as the
time when age-associated deficits are
manifested. Dr. Davidovic et al discuss
the role of genetic instability in aging
and dynamics of the aging process.

16. ii. Endocrine Theory.
Biological clocks act through hormones to
control the pace of aging. Recent studies
confirm that aging is hormonally regulated
and that the evolutionarily conserved
insulin/IGF-1 signaling (IIS) pathway plays
a key role in the hormonal regulation of
aging. Dr. van Heemst discusses the
potential mechanism underlying IIS and
aging process.
Examples:
-Human growth hormone (GH) levels
decrease with age.
-Sex hormones like estrogen and
testosterone levels also fall off.

17. The endocrine theory assumes that
impaired hypothalamus-pituitary gland-
endocrine systems which regulate
homeostasis in the body are the main
cause of aging and further has many
broad effects on many physiological
functions in the body. Generally,
endocrine hormones participate in
controlling growth, metabolism,
temperature, inflammation, and stress

18. iii. Immunological Theory.
The immune system is programmed to decline over
time, which leads to an increased vulnerability to
infectious disease and thus aging and death. It is well
documented that the effectiveness of the immune
system peaks at puberty and gradually declines
thereafter with advance in age. For example, as one
grows older, antibodies lose their effectiveness, and
fewer new diseases can be combated effectively by the
body, which causes cellular stress and eventual death.
Indeed, dysregulated immune response has been linked
to cardiovascular disease, inflammation, Alzheimer’s
disease (AD), and cancer.

19. Although direct causal relationships have not been established for all these
detrimental outcomes, the immune system has been at least indirectly
implicated
Example:
- Lower rate of T –Lymphocyte ("killer cells") proliferation in response to
stimulus, there for a decrease in the body defense against foreign
pathogens.
- It is well documented that the effectiveness of the immune system peaks
at puberty and gradually declines thereafter with advance in age.

20. iv. metabolic theory (caloric
restriction)
- Proposes that all organisms have
a finite amount of metabolic
lifetime and that organisms with a
higher metabolic rate have a
shorter life span.
- Rodent –based research has
demonstrated that caloric
restriction increases the life spans
and delays the onset of age –
dependent disease.

22. v. DNA-Related Research
Mapping the human genome ("…. there may be as
many as 200 genes responsible for controlling
aging in humans")
Discovery of telomeres:
1-Telomeres are specialized DNA sequences at the
end of chromosomes.
- They shorten with each cell division.
- When the telomeres become too short, the cell
enters the senescence stage.
2- In the normal process of DNA replication, the
end of the chromosome is not copied exactly,
which leaves an replicated gap.
3- The enzyme, telomerase, fills the gap by
attaching bases to the end of the chromosomes.

23. 4- As long as the cells have enough
telomerase
to do the job, they keep the telomeres
long
enough to prevent any important
information
from being lost as they go through
each replication.
Shortened telomeres are found in:
- Atherosclerosis
- Heart disease
- Hepatitis
- Cirrhosis

24. Empirical Evidence Supporting Programmed
Aging and a Treatable Common Cause
There is now extensive empirical evidence that
aging is programmed and that there are treatable
causes common to many or most manifestations of
aging.
- Exercise, caloric restriction, and diet changes are
widely thought to generally affect aging in
mammals.
- Explicit suicide mechanisms have been found in
some organisms such as octopus and roundworm.

26.  Human genetic diseases
Hutchinson-Guilford progeria and
Werner’s syndrome
simultaneously accelerate many or
most symptoms of aging including
age-related diseases
suggesting a defect in a common
mechanism that controls
the diverse symptoms

27. II. The damage or error theory include
i. Wear and tear theory:
The wear and tear theory of aging was first introduced by Dr.
August Weismann, a German biologist, in 1882, it sounds
perfectly reasonable to many people even today, because this
is what happens to most familiar things around them.
It is proposed that damage to vital irreplaceable body parts
leads to death of cell ,tissue ,organ &finally the whole body.

28. Wear-and-tear theory
Like machines become damaged and eventually break
down when utilized for a certain period of time, the wear-
and-tear theory proposes that the human body also
undergoes aging due to damage from accidents, diseases,
radiation, toxic substances, food, and many other harmful
substances when it is utilized for a long time. However,
the theory has been rejected because animals protected
from the damages also age without any alteration of their
maximum lifespan, and therefore, such damages are not
the factors causing aging but just time-dependent changes

29. Example:
It is very logical because it is what happens to
the nonliving things that people observe around
them (i.e. components of an aging car break due
to repeated use)
Cells and tissues have vital parts that wear out
resulting in aging.
Parts of the body eventually wear out from
repeated use
killing the parts and then the body.
When we age our bodies have decreased ability
to repair any damages that occur through-out
lives.

30. .
It states that people (and other living
organisms) have a finite number of
breaths, heartbeats, or other
measures, and that they will die
once they've used those up.
But don't try to live longer by
slowing your metabolism just yet:
while the theory is helpful to explain
some aspects of aging, it doesn't
really hold up under modern
scientific scrutiny.

31. Studies have demonstrated that rats kept on restricted diets
and in cold environments live longer.
However, the theory can only partially explain the
differences in life span between species, and it cannot
explain the most important factor: what determines
lifespan within species.
For example, if a person lives 100 years, they will have taken
far more breaths, metabolized more oxygen and experienced
more heartbeats than someone who only lives until 80. What
we want to know, from a longevity perspective, is what
determines which individuals within a species live the
longest.

32. example
There really isn't data that slowing the metabolism
extends human life.
In fact, a slower metabolism would put someone
at risk for obesity and other nutritional-related
illnesses, so your best bet is still a healthy
lifestyle with plenty of exercise, a diet with lots
of plants, and a positive, relaxed attitude.
The greater an organism’s rate of oxygen basal
metabolism, the shorter its life span.

33. example
 Certain skin cells produce collagen during their
younger, reproductive years. When they reach
senescence and can no longer divide, they produce
collagenase, an enzyme that breaks down collagen.
Some researchers suggest that this process may be
responsible for the thinning and wrinkling of skin as
we age.

34. iii. Cross-linking theory:-
The cross-linking theory of aging was proposed by
Johan Bjorksten in 1942 . According to this theory,
an accumulation of cross-linked proteins damages
cells and tissues, slowing down bodily processes
resulting in aging.
Recent studies show that cross-linking reactions are
involved in the age related changes in the studied
proteins . DNA &other molecules develop
inappropriate attachment to one another and broken
down by enzymes
but the presence of cross-linked prevent the activity
of the enzymes

35.  Example:-
Living a longer life is going to lead to the
increased possibility of oxygen meeting glucose
and protein and known cross-linking disorders
include senile cataract and the appearance of
tough, leathery and yellow skin

36. iv. Free radicals' theory: -
This theory, which was first introduced
by Dr. Gerschman in 1954, proposes that superoxide
and other free radicals cause damage to the
macromolecular components of the cell, giving rise to
accumulated damage causing cells, and eventually
organs, to stop functioning.
The macromolecules such as nucleic acids, lipids,
sugars, and proteins are susceptible to free radical
attack. Nucleic acids can get additional base or sugar
group; break in a single- and double-strand fashion in
the backbone and cross link to other molecules.

37. The body possess some natural antioxidants in the
form of enzymes, which help to curb the dangerous
build-up of these free radicals,
without which cellular death rates would
be greatly increased, and subsequent life
expectancies would decrease.

38. Many researchers shows that
reactive oxygen species (ROS)
signaling is probably the most
important enzyme/gene pathway
responsible for the development
of cell senescence and
organismal aging and that ROS
signaling might be considered as
further development of free
radical theory of aging

39. v. Somatic DNA damage theory.
DNA damages occur continuously in cells
of living organisms. While most of these
damages are repaired, some accumulate, as
the DNA Polymerases and other repair
mechanisms cannot correct defects as fast
as they are apparently produced. In
particular, there is evidence for DNA
damage accumulation in non-dividing cells
of mammals. Genetic mutations occur and
accumulate with increasing age, causing
cells to deteriorate and malfunction.
Damage to mitochondrial DNA might lead
to mitochondrial dysfunction. Therefore,
aging results from damage to the genetic
integrity of the body’s cells.

40. Example
Some neurological diseases are considered to
be at high risk with increasing age, for example,
AD, which is diagnosed in people over 65 years of
age.
According to telomere theory, telomeres have
experimentally been shown to shorten with each
successive cell division .

41. Implications for Medicine
We cannot really understand cancer or other
massively age-dependent disease without
understanding aging.
The major medical question is whether there exist
potentially treatable factors that are common to two
or more major manifestations of aging.
Simple deterioration and non-programmed theories
suggest there is no treatable common factor –
continues existing main-line medical thinking.

42. Programmed theories suggest existence of controlling
mechanisms (signaling, sensing, etc.) that are common
to multiple symptoms and therefore existence of
treatable common factors. Direct observational
evidence supports this (progeria, caloric restriction,
aging genes, etc.)
The theories point in very different research directions:
disease-specific damage mechanisms vs. common
lifespan regulation mechanism.
Continued non-resolution of the programmed/ non-
programmed issue damages the credibility (and
funding level) of age-related medical research efforts.

43. Anti-Aging Behaviors
The good news is that many of the
causes of aging that may be happening
prematurely can be modified through
your behaviors.
Here are a few ways to keep your body
feeling as young as possible:
 Eat foods loaded with antioxidants to
minimize damage caused by free
radicals.
 Exercise regularly to limit bone and
muscle loss.
 Keep your cholesterol low so you can
slow the hardening of your arteries
and protect your heart.
Practice mental fitness to keep your brain
sharp.

44. Theories of aging can be divided into two
categories: those that answer the question
“Why do we age?” and those address
the question “How do we age?” Only a few
theories attempt to explain why we and nearly all
living organisms age. These theories compete with
each other, making it unlikely that more than one of
them could be true. Over time, some theories have
fallen out of favor as others have become more widely
accepted .