Physiology of Aging

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Physiology of Aging
John Puxty, Queens University puxtyj_at_post.queensu.
ca
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Learning Objectives

• By the end of this section, the student will
  appreciate the importance of
• physiological and psychological factors that
  contribute to normal aging,
• the difference between normal aging and the
  diseases of aging.
• frailty and co-morbidity in the presentation of
  disease in the elderly

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Normal Aging

• Despite stereotype most of the elderly age well!

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Normal Aging

• Despite stereotype most of the elderly age well!
• Most of our images are based on the frail sub-set
  who frequently use medical services

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Normal Aging

• Despite stereotype most of the elderly age well!
• Most of our images are based on the frail sub-set
  who frequently use medical services
• Generally normal aging in associated with a
  reduction in functional reserve capacity in
  tissues and organs

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Age related change in function reserves
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Normal Aging

• Despite stereotype most of the elderly age well!
• Most of our images are based on the frail sub-set
  who frequently use medical services
• Generally normal aging in associated with a
  reduction in functional reserve capacity in
  tissues and organs
• At advanced age more common to see evidence of
  impaired homeostasis and response to external
  insults eg illness

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Traditional medical approaches do not cater for
the heterogeneity of disease in the elderly!
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Skin and Aging

• In general, the skin tends to become drier,
  thinner, and more wrinkled with age. Other
  age-related changes include
• Loss of the inter-digitations between the
  epidermis and dermis, leading to ease of tearing
  or breakdown (see picture opposite).
• Decline in the vascular supply which influences
  thermoregulation as well as drug absorption and
  the response to toxic substances.
• Decline in the immune cells of the integument.
• Decline in the activation of Vitamin D.

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Skin and Aging
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Consequences of Aging Skin

• Older skin tends to be more vulnerable to
  tearing, bruising, and breakdown.
• Pressure ulcers (decubiti), are seen more
  commonly within the hospitalized elderly.
• There may be delayed response to
  topically-administered toxic agents.
• Exposure to sunlight exacerbates age-related
  changes in the skin.

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Cardiac Output and Age
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Heart Rate and Age
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Cardiovascular

• Higher Syst. BP more common
• Reduced ability to increase HR
• Increased postural hypotension
• Prone to diastolic dysfunction

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Presentation Of CCF

• Prevalence of 10 80 years group
• Often atypical weakness, fatigue, weight loss,
  confusion
• Often associated with pneumonia, AF, Thyroid
  disease, Renal Disease
• Medication usage often factor in precipitation
• 50 have normal LVEV (diastolic dysfunction)

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Respiratory

• Increased energy of breathing
• Increased airways resistance
• Increased in dead-space
• Reduced V/Q ratio

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Sensory (1)

• Vision
• The lens tends to opacify, which influences color
  perception.
• There is a decrease in light and dark adaptation.
  
• The lens tends to lose elasticity, which
  increases the distance of focusing.
• There is a decline in contrast sensitivity and an
  increase in sensitivity to glare.

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Sensory (2)

• Hearing
• Hair cells tend to be lost in the organ of Corti.
  
• Cochlear neurons tend to be lost.
• Stiffening, thickening, and calcification occur
  in multiple components of the auditory apparatus.
  
• Taste
• Older persons may have decreased sensitivity to
  taste.

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Neuromuscular

• Reduced sensory input including propio-ceptive
  information
• Delayed nerve conduction
• Reduced numbers of motor neurones
• Reduced fast twitch fibres
• Reduced muscle mass

Therefore vulnerability to falls!
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Osteoporosis and Fractures

• Low dietary intake of Calcium
• Loss of endocrine protection
• Reduced endogenous production of Vitamin D
• Disuse
• Disease Chronic Renal Disease, Rheumatoid
  Arthritis, Thyroid Disease
• Medications Steroids, Thyroxine

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Sobering Facts re Falls in Elderly

• 4,821 per 100,000 pop. over 65 attend AE with
  falls and almost 25 resulted in hospitalization
• 90 of fallers sent home from AE have no
  change in fall-risk factors
• 40 of Fallers presenting to AE will within
  one year
• Life time risk for hip in males 11 and females
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• Estimated in 2001 one year cost of hip was
  26,527 (21,365 in those -gt community and
  44,156 -gt LTC)

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Sobering Facts (2)

• Less than 40 of hip patients will regain
  previous level of ambulation!
• 7 short-term mortality rising to 20-35 after
  one year!
• Restraints increase incidence of serious falls
• 40 of admissions to LTC are frequent fallers
• Fall rate increases in first six weeks in LTC!

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The Digestive System

• Stomach
• motility
• pH
• Sm. Intestine
• absorption
• Large Intestine
• motility
• Liver
• blood flow
• cytochrome P 450

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Renal

• General decline in glomerular filtration rate by
  about 8-10ml/min per 1.73m2 per decade after age
  30-35.
• Progressive decline in ability to excrete a
  concentrated or a dilute urine
• Delayed or slowed response to sodium deprivation
  or a sodium load
• Delayed or sluggish response to an acid load

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Pharmacokinetics and Aging

• Absorption - gastric pH higher, decreased
  motility and absorption
• Distribution - reduced total body water, proteins
  and lean body mass, and increased total body fat
• Metabolism - hepatic oxidative pathways impaired
  (benzodiazepines) and P-450 (B-blockers, TCAs,
  verapamil)
• Excretion - reduced GFR and change in tubular
  function (aminoglycosides, lithium, digoxin)

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• Low Body Water -gt reduced vol. of dist. for polar
  drugs eg. Aminoglycocides, Digoxin
• High Fat Stores -gt increased vol. of dist. for
  lipid soluble drugs eg. Phenytoin, Diazepam,
  Flurazepam

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Pharmacokinetics and Aging

• Absorption - gastric pH higher, decreased
  motility and absorption
• Distribution - reduced total body water, proteins
  and lean body mass, and increased total body fat
• Metabolism - hepatic oxidative pathways
  (benzodiazepines and P-450 (B-blockers, TCAs,
  verapamil)
• Excretion - reduced GFR and change in tubular
  function (aminoglycosides, lithium, digoxin)

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Pharmacodynamics(effect of drugs at target site)

• No generalization regarding receptor numbers or
  affinity or hormone levels
• Examples of changes are insulin receptors, Beta
  receptors and heart, Ach receptors and colon

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Genitourinary (men)

• Decreased blood flow may lead to a decrease in
  erectile function.
• Spermatogenesis continues, although sperm count
  tends to decline and chromosomal abnormalities
  tend to increase.
• The prostate tends to increase in size, and
  prostatic fluid tends to decrease in amount.

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Genitourinary (women)

• Reproductive capacity is lost at the time of
  menopause.
• Ovary, uterus, and vagina tend to atrophy
  following menopause
• The urethra is more likely to be colonized by
  gram negative organisms.
• Alterations in mucosa lead to increased bacterial
  adherence.

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Newer results...

• The Starr-Weiner report
• 97 liked sex
• 91 approved of unmarried/widowed aged having sex
• quality more important than frequency!
• Women in survey had intercourse 1.4/week

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Newer results...

• Large proportion of seniors sexually active
• 54 of married men women
• 65 of women over age 70
• Netherlands 34 of women surveyed enjoy sexual
  activity most of time
• Vs. 70 of premenopausal women

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What problems may women report

• 43 of older Swedes reported vaginal dryness
• 10 vaginal burning
• urinary incontinence may occur
• dyspareunia
• decreased orgasm (30)

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What changes for men?

• Changed libido
• erectile function
• increased need for stimulation
• inadequate rigidity associated with risk factors
• decreased ejaculatory demand
• decreased ejaculatory power
• prolonged refractory stage (up to one week)

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Impact of Physiological and Epidemiological
Factors in the Elderly and the Health Care System

• John Puxty, Queens University

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Atypical presentations of disease are frequently
seen

• Classical
• Silent
• Pseudosilent
• Atypical Presentations Weakness/Fatigue
  Dwindles Falls/Immobility Incontinence
  Cognition/Mood Change Social Crisis

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High users have overlap of physical and social
vulnerabilities
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Predictors of Frailty

• Extreme age
• Visual loss
• Impaired cognition/mood
• Limb weakness
• Abnormalities of gait and balance
• Sedative use
• Multiple chronic diseases

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Acute illness superimposed on Frailty

• Multiple organ stress
• Failure of homeostasis
• potential exacerbation of chronic diseases
• Increased potential for drug interactions and
  adverse effect
• Increased vulnerability to delirium, falls and
  incontinence with caregiver stress

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Significance of the Atypical Presentation

• Presence associated with delay in diagnosis and
  increased mortality (Puxty et al 1984)
• Predictive of future functional declines in
  community elderly (Choo-Cho et al 1998)
• Functional decline (dwindles) increases
  likelihood of further decline and increased
  mortality (Hebert et al1997)

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Clinicians general approach to the Atypical
Presentation

• Consider recent change in function a result of
  disease or drugs until proven otherwise
• Longitudinal multiple assessments often necessary
• Additional informants often invaluable
• Appropriate screening investigations have a role
• Multiple pathologies are the rule

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Small changes can result in major functional
gains!
Medications Foot wear Walking aides Surface
heights Chairs/bed Wall bars Lighting Flooring/mat
s
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Conclusions

• Aging of the population will result in 25 of the
  population being over 65 by 2030
• The majority of the elderly are well and enjoy a
  reasonable socio-economic status
• A small but significant subset of frail,
  vulnerable elderly account for an excess of
  adverse socio-economic and health care outcomes
• A typical profile is the very old, female, living
  alone, with multiple chronic diseases and taking
  multiple medications
• The presence of acute illness should be suspected
  with recent unexpected functional decline