Physiology of AgingPhysiology of Aging

John Puxty, Queens Universitypuxtyj@post.queensu.ca

Learning ObjectivesLearning 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

Normal AgingNormal Aging

Despite stereotype most of the elderly age well!

Normal AgingNormal 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

Normal AgingNormal 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 is associated with a reduction in functional reserve

capacity in tissues and organs

Age related change in function Age related change in function reservesreserves

Normal AgingNormal 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 (e.g. illness)

Traditional medical approaches do not cater for the heterogeneity of disease in

the elderly!

Skin and AgingSkin 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.

Skin and AgingSkin and Aging

Consequences of Aging SkinConsequences 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.

Cardiac Output and AgeCardiac Output and Age

Heart Rate and AgeHeart Rate and Age

CardiovascularCardiovascular

Higher Syst. BP more common

Reduced ability to increase HR

Increased postural hypotension

Prone to diastolic dysfunction

RespiratoryRespiratory

Increased energy of breathing Increased airways resistanceIncreased in dead-spaceReduced V/Q ratio

Sensory (1)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.

Sensory (2)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.

NeuromuscularNeuromuscular 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!

Osteoporosis and FracturesOsteoporosis 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

Sobering Facts re Falls in ElderlySobering Facts re Falls in Elderly

4,821 per 100,000 pop. over 65 attend A&E with falls and almost 25% resulted in hospitalization

90% of “faller”s sent home from A&E have no change in fall-risk factors

40% of Fallers presenting to A&E will # within one year

Life time risk for hip # in males 11% and females 27%

Estimated in 2001 one year cost of hip # was $26,527 ($21,365 in those -> community and $44,156 -> LTC)

Sobering Facts (2)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 falls40% of admissions to LTC are “frequent

fallers”Fall rate increases in first six weeks in LTC!

The Digestive SystemThe Digestive System

• Stomach motilitypH

• Sm. Intestineabsorption

• Large Intestinemotility

• Liver•blood flow

RenalRenal

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

Pharmacokinetics and AgingPharmacokinetics 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, TCA’s, verapamil)

Excretion - reduced GFR and change in tubular function (aminoglycosides, lithium, digoxin)

Low Body Water -> reduced vol. of dist. for polar drugs eg. Aminoglycocides, Digoxin

High Fat Stores -> increased vol. of dist. for lipid soluble drugs eg. Phenytoin, Diazepam, Flurazepam

Pharmacokinetics and AgingPharmacokinetics 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, TCA’s, verapamil)

Excretion - reduced GFR and change in tubular function (aminoglycosides, lithium, digoxin)

PharmacodynamicsPharmacodynamics((effect of drugs at target siteeffect 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

Genitourinary (men)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.

Genitourinary (women)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.

Newer results...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

Newer results...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

What problems may women What problems may women reportreport

43% of older Swedes reported vaginal dryness

10% vaginal burningurinary incontinence may occurdyspareuniadecreased orgasm (30%)

What changes for men?What changes for men?

Changed libidoerectile function

– increased need for stimulation– inadequate rigidity associated with risk factors

decreased ejaculatory demanddecreased ejaculatory powerprolonged refractory stage (up to one week)

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

SystemSystem

John Puxty, Queen’s University

Atypical presentations of disease Atypical presentations of disease are frequently seen are frequently seen

Classical Silent Pseudosilent Atypical Presentations

Weakness/FatigueDwindles Falls/Immobility

IncontinenceCognition/Mood ChangeSocial Crisis

High users have overlap of High users have overlap of physical and social vulnerabilitiesphysical and social vulnerabilities

Predictors of FrailtyPredictors of Frailty

Extreme ageVisual lossImpaired cognition/moodLimb weaknessAbnormalities of gait and balanceSedative useMultiple chronic diseases

Acute illness superimposed Acute illness superimposed on Frailtyon Frailty

Multiple organ stress Failure of homeostasispotential exacerbation of chronic diseasesIncreased potential for drug interactions and

adverse effectIncreased vulnerability to delirium, falls and

incontinence with caregiver stress

Significance of the Significance of the “Atypical Presentation” “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)

Clinician’s general approach Clinician’s general approach to the “Atypical Presentation”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 invaluableAppropriate screening investigations have a

roleMultiple pathologies are the rule

Small changes can result in major functional gains!

MedicationsFoot wearWalking aidesSurface heightsChairs/bedWall barsLightingFlooring/mats

ConclusionsConclusions 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