2. Aging: theory and trends Flashcards
REVIEW:
- biological aging OR __________ refers to what?
- age-related diseases and conditions are those in which incidence/severity drastically increase with ________ –> examples! (10)
- or senescence –> refers to gradual deterioration of systems as a function of age seen in humans and other organisms –> at a cellular level –> tissues –> systems –> body functions
- age!
- heart disease, stroke, Alzheimer’s disease, osteoarthritis, osteroporosis, sarcopenia, cancer, decline in reproductive ability, reduced immunity, sensory loss
what are some inevitable physiological changes with aging (7)? –> vs what happens when you pass a certain threshold? –> prevalence?
DECREASED MUSCLE MASS
- sarcopenia (10%)
- mobility issues (15%)
DECREASED BMD
- osteoporosis (15.9% women, 1.7% men)
- osteoarthritis (90% of women, 80% of men older than 65, mostly hands)
INCREASED FAT MASS
- obesity (39.5%)
- osteoarthritis (85%)
DECREASED MUSCLE STRENGTH
- dynapenia (31.4%)
- mobility issues (15%)
INCREASED BP
- CV disease (#1 cause of death) (49%)
DECREASED LUNG CAPACITY
- COPD (3.5%)
INCREASED INSULIN RESISTANCE
- diabetes (8.5%)
which aging conditions have the highest prevalence? vs lowest?
- osteoarthritis from decreased BMD (90% of women, 80% of men older than 65, mostly hands)
- osteoarthritis from increased fat mass (85%)
- CV disease (#1 cause of death) (49%)
- obesity (39.5%)
- dynapenia from decreased muscle strength (31.4%)
- osteoporosis (15.9% women, 1.7% men)
- mobility issues (15%)
- sarcopenia (10%)
- diabetes (8.5%)
- COPD (3.5%)
compare primary vs secondary aging
PRIMARY (or senescence)
- unavoidable deterioration of cellular structure and function independent of disease and environmental factors
SECONDARY aging:
- cellular deterioration due to preventable lifestyle and environment exposures
- pathological cause
- lifestyle and environmental factors play an important role in the process –> ie dietary habits, PA, smoking, sun exposure –> if done well, could possibly slow down normal/1° aging
- could hypothetically never occur
what are 3 causes of aging ish
- disuse (decrease in PA) –> could be as detrimental as genetic predisposition to disease
- age-related causes
- disease related factors
what are the 2 main categories of stages of aging + their subranges (3 + 4)
ADULTHOOD
- early: 20-29
- middle: 30-44 (most aging changes start here ish)
- late: 45-64
AGING/SENESCENCE
- young-old: 65-74
- old: 75-84
- old-old: 85-99
- oldest-old: 100+ years
CELLULAR SENESCENCE
- definition
- leads to what?
- can be triggered by (5)
- decrease in cell function or inability of cells to divide/repair
- leads to deterioration of tissues, organ function, organ systems, and homeostasis of organism
- can be triggered by numerous stimuli, including, but not limited to:
a) progressive telomere shortening/changes in telomere structure (shorten with each cell division)
b) DNA damage
c) oxidative stress (increase ROS)
d) oncogene activation
e) mitochondrial dysfunction
- in most severe state, senescence can lead to what? and eventually (A)
- is (A) always bad? (2)
- 2 main mechanisms of (A)
can lead to permanent arrest of cellular growth, and eventually cell death
NOT all cell death is bad!
- allows removal of damaged cells
- eliminates cells that are no longer needed
a) apoptosis or programmed cell death –> involves membrane protrusions + a controlled shrinking of the cell –> engulf by white blood cell, which avoids eliciting inflammation
- quite normal, to maintain healthy cells
b) necrosis or uncontrolled cell death results from environmental perturbations (ie infection, disease, radiation) and involves the release of inflammatory cell contents in the tissue (to surrounding cells to!)
- swelling of cell + rupture of cell –> enzymatic digestion + leakage of cellular contents into neighbouring cells = inflammation
- “unhealthy” cellular death, ie in stroke, or gangrene in diabetes
what is the link btw senescence and cell death? (3)
describe schéma!
- accumulation of senescent cells may contribute to the age-dependent increase in disease incidence
- apoptosis plays a key role in eliminating dysfunctional or cancerous cells and preventing abnormal tissue growth (ie tumours) during senescence
- necrosis occurs due to infiltration by lethal stressors (infection, toxins)
normal replication cell:
a) moderate stress: becomes senescent cell –> can lead to b) and c)
b) large stress: apoptosis
c) lethal stress: necrosis
what are 4 consequences of senescence on a systems level?
- functions totally los
- ie reproduction and menstruation, hearing and other sensory loss - structural changes
- loss of motor neurons, decrease fast-twitch muscle fibers (switch to more slow twitch to promote endurance - reduced efficiency of a unit
- decreased nerve conduction velocity - altered control systems (hormones)
- cessation of estrogen production by ovaries
- homeostasis definition
- what happens to it when you age? result?
- what refers to a diminished ability to maintain homeostasis, especially under stress (ie disease, exercise)? explain
- maintenance of relatively stable internal physiological conditions (blood gluc, body temp…) –> through feedback loops
- aging results in an increased time for equilibrium (ie increase response time) and loss of adaptability and precision of control systems
RESULT: biological control systems no longer maintain an optimized internal environment = homeostenosis - homeostenosis! –> receptors, regulatory centres, and feedback loops no longer function with the same efficiency observed in a healthy younger bodily system
AGING AND HOMEOSTASIS
explain schéma:
- increasing age on x-axis
- what is on y-axis?
- what does curve represent?
- stress at lower age vs stress at higher age
- y-axis = physiological reserves (of any system in the body)
- curve = physiological limit: limit beyond which homeostasis cannot be restored –> high at young age and slowly decreases
a) stress at lower age: goes to like 60% of physiologic reserve –> able to restore homeostasis
b) stress at higher age: goes to 110% of physiologic reserve (even if stress is same amount as a)) –> results in acute injury or disease state bc homeostenosis –> leads to lack of independence
modern aging theories attempt to do what? (2)
- strehler and colleagues state that aging is not caused by ________but due to ________________
- how many theories?
- earliest aging theory by who? what is it?
- identify common causes and explain why similar species exhibit drastically different life spans despite exhibiting similar manifestations of aging
- 1959: aging is not caused by any single factor but due to an aggregate of causes
- more than 300 theories!
- Hippocrates (460-377 BC) –> aging is an irreversible and actual event caused by gradual loss of heat
define lifespan
- similar or different btw species?
- lifespan refers to the internally determined amount of time a member of species population can be expected to live in the absence of any external limitations on survival (ie predation, lack of food/habitat, infectious diseases, severe environmental conditions)
*in most developed countries, many human deaths are related to the aging process - lifespan is similar for the same species. different species have different lifespans
name 4 aging theories
- evolutionary aging theories
- damage theories (include free radical theory, mechanical wear and tear theory, chemical accumulation theory, telomere theory)
- non-programmed aging theories
- programmed aging theories
EVOLUTIONARY AGING THEORIES
- what?
- based on what? explain
- limitations? (3)
- evolutionary aging theories attempt to explain how aging (senescence) relates to the evolution process and why biochemically similar species have very different internal determined lifespans
- based on Charles Darwin’s natural selection theory: the evolution process is caused by organisms with favorable design characteristics/trait which can produce adult descendants with higher probability than those without the trait
a. aging doesn’t help individual humans and other mammals to survive or reproduce despite otherwise resembling a trait
b. Darwin’s natural selection theory suggests that the force of evolution tends toward developing internal immortality, or the absence of any internal limitation on lifespan
c. have difficulty explaining how and why species have a limited lifespan (ie humans vs rodents)
DAMAGE THEORIES:
- suggest that what?
- examples of proposed damage theories (4) + explain
- Suggest that senescence is caused by a damage process that is general vs. disease-specific, causing many or all age-dependent manifestations
a) Free radical theory: - oxidative damage accumulates with age and lead to cumulative DNA, protein, and lipid damage over a lifespan
b) Mechanical wear and tear theory - systems (e.g., cells, organs) wear out and stop functioning with continued use
c) Chemical accumulation theory: - aging is caused by an accumulation of chemical damage
d) Telomere theory: - progressive shortening of telomeres on DNA cause cells to lose their ability to divide and function
what are 2 limitations of damage theories?
- living organisms are known to have extensive repair capabilities, most damage theories ignore this
- fail to explain the significant lifespan differences btw biologically and physically similar species with similar exposure to the damage process (ie why doesn’t everyone’s hips breakdown at 70 yo?)
NON-PROGRAMMED AGING THEORIES
- what?
- 3 proposed theories
- These theories suggest that aging is the result of an organism’s inability to combat natural deteriorative processes
a) Mutation accumulation theory:
- harmful mutations are only expressed later in life when reproduction has ceased and future survival is increasingly unlikely and are therefore retained in future generations
b) Antagonistic pleiotropy theory:
- certain genes that benefit early life but impair later life are selected for because senescence is rare in the wild
c) Disposable soma theory:
- organism could be designed to reduce repair activities at a species-specific age
what are the strengths (2) and limitations of the non-programmed aging theories? (2)
STRENGTH
- They are compatible with factors affecting longevity (i.e., cellular damage, epigenetic modulation)
- accounts for existence of repair mechanisms (vs damage theory)
LIMITATIONS:
- Require significant modifications to Darwin’s concepts
- Suggest that aging is a side effect of something else and there is NO potentially treatable common factor behind the many age-related diseases and conditions –> doesn’t think about lifestyle factors that can prevent aging
PROGRAMMED AGING THEORIES
- suggests that what?
- explain
- what is a super important concept?
- Suggest that the lifespan is largely determined by the genes we inherit and how they respond to external conditions
- There is a biological need for both senescence and non-senescence at different population-specific times in an organism’s life, and senescence would need to be applied to diverse organism tissues and systems following a species-unique schedule
- biological clock: detects external conditions and adjusts to accommodate local or temporary conditions that affect the optimum lifespan
explain the schéma of programmed aging theories (3 steps ish)
- external conditions –> common aging program: biological clock + detect external conditions + generate control signals
- common aging program –> signals many repair processes in diverse tissues
- those repair processes –> species-specific senescence and life span adjusted by local or temporary conditions
what are the strengths (2) and limitations of the programmed aging theories? (2)
STRENGTH:
- There is increasing evidence that genes influence aging and longevity, including genetic diseases that accelerate aging
- Potentially alterable common factors exist in the aging process and can lengthen the lifespan
LIMITATIONS:
- Programmed aging would be an evolutionary disadvantage because it would kill the individual without any group/species-level benefit
- Mutations could inactivate gene-controlled mechanisms associated with aging and death
*focuses on individuals, not species
review case study activity!
summary of aging theories
- there are many aging theories –> is there strong scientific agreement on any one theory?
- non-programmed aging theories suggests that symptoms of senescence are_________________ of each other, aging CAN/CANNOT be delayed/reversed by interventions (meds, diets, exercise)
- programmed aging theories suggest that what?, and therefore senescence is what?
- many modern scientific discoveries tend to support which theories?
- NO strong scientific agreement on any one theory
- independent of each other –> aging CANNOT be delayed by interventions
- that a common biological mechanism is responsible for diverse aging manifestations AND therefore senescence is a treatable condition
- support programmed aging theories
- population aging is a process whereby what happens (2)
- seniors make up to ___% of NA pop
- almost ___% of health care go towards their needs
- more than ____% of those individuals aged 65 yo are limited in daily activities due to what?
- what are 2 strategies that must meet the needs of this growing subset of the pop?
- populations transform from a younger to an older age structure and the proportion of individuals this is of older age increases
- 12%
- 30% health care
- more than 25% –> due to health problems
- prevention and treatment!
which countries/continents have the highest % of 70 yo and +?
- why is older population increasing (2)
- Japan = extreme, China = rapid
- US = progressive
- India delayed (similar to world level)
- Nigeria = slow
decrease decrease birth rate + decrease mortality rates
- what is driving the shift toward an older demographic? explain. reasons (4)
FERTILITY DECLINE!
- people are having, on avg, progressively fewer children (fewer births) relative to size of population
- 1.5 children per women aged 15-49 yo
a) urbanization
b) increasing education
c) changing gender norms
d) increasing economic contributions by women
e) other factors related to modernization of society
what is another contributor of global shift in aging demographics, apart from fertility decline? exaplin
mortality decline!
- probability of dying at any particular age is decreasing in time
- rapid population aging occurs when birth rates fall sharply at some point after death rates have declined
do females or males live longer? why? (3 broad categories, 5 in total)
females!
- genetic factors: females have 2 X chromosomes and more optimized mitochondrial/cellular DNA –> protective against recessive genes and reduce cellular dysfunction! (ie if there are faulty genes/mutations, have more DNA
- hormonal/physiological factors –> protective effect of estrogen (protect bone, muscle, CV) + females have more robust immune systems
- environmental/sociocultural factors: differences in work roles and family responsibilities + better lifestyle habits and use of health care services
- given that health is often associated with age, the combination of (2) may contribute to societal burden
- 80-90% of seniors living at home suffer from __________________
- describe graphs ish
- combination of rapid population aging and increasing longevity
- > =1 chronic conditions!
- for both males and females, as age increases, increase in people with more than 1 chronic condition
describe the aging cycle of PA (6 steps)
- what is the role of PA for middle-aged/late, young-old, old, old-old, oldest-old?
increase age –> less exercise –> decreased physical abilities –> social and psychological aging –> further decrease in PA –> physical deterioration –> increase age
middle-aged/late: 45-65:
- a) maintain physical performance
- b) postpone aging
- c) reduce risk of age-related disease
YOUNG-OLD (65-74)
- a) b) c)
- d) enhance QoL and independence
OLD (75-84):
- a), c), d)
OLD-OLD (85-99):
- reduce implications of age-related disease (manage disease)
- enhance qualify of life!
OLDEST-OLD (100+)
- same as Old-old
what type of older adults are particularly inactive? (6)
- low incomes and education levels
- older seniors (>80 yo)
- those living in institutionalized care (nursing home, long-term care)
- seniors with chronic disease/disability
- older women
- socially isolated persons
what are the 3 most prevalent responses of PA completed in community-dwelling older adults?
- walking! 20-29% ish
- light housework (23-24%)
- heavy housework (14-19%)
*also resistance training, caregiving duties, yardwork, gardening, moderate-vig activities, home repair
define sedentary behaviour
- older adults spend ___% of their day doing sedentary activities (vs ___% in nursing homes)
- high sedentary time associated with (3) independent of what?
- sitting time, sedentary time, sedentary living and physical inactivity where <1.5 METs
- 80% vs 89% in nursing homes
- associated with metabolic syndrome, obesity and low physical function –> independent of time spent in mod-vig PA
- what are the trends for men and women for sedentary time, light PA, mod PA, vig PA, MVPA, step count, as age increases (20-39, 40-59, 60-79)?
- trends for more than 150min/wk of MVPA? (20-39, 40-59, 60-79)?
- for avg more than 10k steps/day
for both women and men:
- sedentary: increase
- light, mod, vig, MVPA, step count –> all decrease as age increases!
- although 20-39 and 40-59 is similar for both men and women
- 17.4% –> 14.6% –> 13.10%
- 36.2% –> 40% –> 20.3%
do older adults adhere to strength training? stats
- 12% strength training
- 6% balance training
- 21.8% balance-challenging activities
- only 5.3% adhered to strength and balance exercise >2 days/week
other study: 32.5% of active older adults reported engaging in strength training 1-7 days per week
what are the similarities/differences btw 24h movement guidelines btw 18-64 and 65+?
similarities:
- 150min/wk mod-vig activity
- muscle strengthening >=2x/wk
- several hours of light PA, including standing
- limit sedentary time to 8h or less –> no more than 3h recreational screen time + breaking up long periods of sitting as often as possible
differences:
- 18-64: 7-9h of sleep with consistent bed and wake-up times
- 65+: 7-8h sleep + PA that challenge balance
SUMMARY: aging and activity trends:
- population aging is a function of (2) leading to what?
- with aging, PA tends to __________ while sedentary behaviour _______ leading to wide-scale _______ in older adults, which is associated with what?
- significant research has determined appropriate levels of PA for older adults to (2)
- of fertility decline (driving force) and mortality decline –> leading to rapid growth in number and proportion of older adults world-wide
- PA decrease, sedentary behaviour increases –> wide-scale inactivity –> associated with increased risk of morbidity and mortality
- to improve or maintain health and functional benefits –> but not a one size fits all
