Physiology of Aging

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Physiology of Aging
John Puxty, Queens University puxtyj_at_post.queensu.
ca
Supplemented by Geriatric online curriculum
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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 changes in functional 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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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 a factor in precipitation
• 50 have normal LVEV (diastolic dysfunction)

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Respiratory

• Increased energy of breathing
• Decreased chest expansion. At about age 55, the
  respiratory muscles begin to weaken.
• In addition, the chest wall gradually becomes
  stiffer, probably as a result of age-associated
  kyphoscoliosis, calcification of intercostal
  cartilage, and arthritis of the costovertebral
  joints.

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Respiratory

• Increased energy of breathing
• Increased airways resistance
• Decrease in the forced expiratory volume at one
  second (FeV1 by 20-30 mL) per year after age 30

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Respiratory

• Increased energy of breathing
• Increased airways resistance
• Increased in dead-space
• Decreased elastic recoil of the lungs

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Respiratory

• Increased energy of breathing
• Increased airways resistance
• Increased in dead-space
• Reduced V/Q ratio
• Airway size decreases with age, and the
  proportion of collapsible small airways
  increases.
• Increase in ventilation-perfusion mismatch in the
  lungs resulting in a decrease in the partial
  pressure of oxygen in blood when breathing room
  air.

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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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Clinical Significance of Aging Eye

• Around age 40, many people will need reading
  glasses to accommodate for the loss of elasticity
  of the lens.
• Cataracts, i.e., opacity of the lens, are common
  in elders, and cataract surgery is the most
  commonly performed surgery in elders.
• Older adults may need longer to adjust when
  entering a dark room or going outside into the
  sun.
• Older adults may need increased contrast to
  facilitate depth perception.
• Diseases such as macular degeneration are common
  in the elderly and particularly impair central
  vision (see diagram opposite).

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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 speed of nerve conduction
• Reduced numbers of motor neurones

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Neuromuscular

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

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Neuromuscular

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

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Neuromuscular

• Reduced sensory input including propio-ceptive
  information
• Delayed speed of 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 (1)

• 40 of Fallers presenting to AE will suffer a
  within one year
• 23,375 Hip s in Canada in 1993/94 (expected to
  rise to 88,125 in 2041)
• Average LOS 21 days so they use at least 465,000
  bed days per year
• 7 short-term mortality rising to 20-35 within
  one year!

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Sobering Facts (2)

• Less than 40 of hip patients will regain
  previous level of ambulation!
• 90 of fallers sent home from AE have no
  change in fall-risk factors
• 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 reduced
• pH increased
• Sm. Intestine
• Absorption ?
• Large Intestine
• Motility reduced
• Liver
• blood flow reduced
• cytochrome P 450 reduced

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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

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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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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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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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Presentation of Disease in the Elderly

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

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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