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Physical Changes With Aging

By

Richard W. Besdine

, MD, Warren Alpert Medical School of Brown University

Last full review/revision Apr 2019| Content last modified Apr 2019
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Most age-related biologic functions peak before age 30 and gradually decline linearly thereafter (see table Selected Physiologic Age-Related Changes); the decline may be critical during stress, but it usually has little or no effect on daily activities. Therefore, disorders, rather than normal aging, are the primary cause of functional loss during old age.

In many cases, the declines that occur with aging may be due at least partly to lifestyle, behavior, diet, and environment and thus can be modified. For example, aerobic exercise can prevent or partially reverse a decline in maximal exercise capacity (oxygen consumption per unit time, or Vo2max), muscle strength, and glucose tolerance in healthy but sedentary older people.

Only about 10% of older adults participate in regular physical activity for > 30 minutes 5 times/week (a common recommendation). About 35 to 45% participate in minimal activity. Older adults tend to be less active than other age groups for many reasons, most commonly because disorders limit their physical activity.

The benefits of physical activity for older adults are many and far exceed its risks (eg, falls, torn ligaments, pulled muscles). Benefits include

  • Reduced mortality rates, even for smokers and the obese

  • Preservation of skeletal muscle strength, aerobic capacity, and bone density, contributing to greater mobility and independence

  • Reduced risk of obesity

  • Prevention and treatment of cardiovascular disorders (including rehabilitation after myocardial infarction), diabetes, osteoporosis, colon cancer, and psychiatric disorders (especially mood disorders)

  • Prevention of falls and fall-related injuries by improving muscle strength, balance, coordination, joint function, and endurance (1)

  • Improved functional ability

  • Opportunities for social interaction

  • Enhanced sense of well-being

  • Possibly improved sleep quality

Physical activity is one of the few interventions that can restore physiologic capacity after it has been lost.

Table
icon

Selected Physiologic Age-Related Changes

Affected Organ or System

Physiologic Change

Clinical Manifestations

Body composition

Lean body mass

Muscle mass

Creatinine production

Skeletal mass

Total body water

Percentage adipose tissue (until age 60, then until death)

Changes in drug levels (usually )

Strength

Susceptibility to dehydration

Cells

DNA damage and DNA repair capacity

Oxidative capacity

Accelerated cell senescence

Fibrosis

Lipofuscin accumulation

Cancer risk

CNS

Number of dopamine receptors

Alpha-adrenergic responses

Muscarinic parasympathetic responses

Tendency toward stiffer muscles, less flexibility, impaired balance, and loss of spontaneous movements (eg, muscle tone, arm swing)

Ears

Loss of high-frequency hearing

Ability to recognize speech

Endocrine system

Insulin resistance and glucose intolerance

↑ Incidence of diabetes

Menopause, estrogen and progesterone secretion

Testosterone secretion

Growth hormone secretion

Vitamin D absorption and activation

Incidence of thyroid abnormalities

Bone mineral loss

Secretion of ADH in response to osmolar stimuli

Vaginal dryness, dyspareunia

Muscle mass

Bone mass

Fracture risk

Changes in skin

Susceptibility to water intoxication

Eyes

Lens flexibility

Time for pupillary reflexes (constriction, dilation)

Incidence of cataracts

Presbyopia

Glare and difficulty adjusting to changes in lighting

Visual acuity

GI tract

Splanchnic blood flow

Transit time

Susceptibility to constipation and diarrhea

Heart

Intrinsic heart rate and maximal heart rate

Blunted baroreflex (less increase in heart rate in response to decrease in BP)

Diastolic relaxation

Atrioventricular conduction time

Atrial and ventricular ectopy

Susceptibility to syncope

Ejection fraction

Rates of atrial fibrillation

Rates of diastolic dysfunction and diastolic heart failure

Immune system

T-cell function

B-cell function

susceptibility to infections and possibly cancer

Antibody response to immunization or infection but autoantibodies

Joints

Degeneration of cartilaginous tissues

Fibrosis

Glycosylation and cross-linking of collagen

Loss of tissue elasticity

Tightening of joints

Susceptibility to osteoarthritis

Kidneys

Renal blood flow

Renal mass

Glomerular filtration

Renal tubular secretion and reabsorption

Ability to excrete a free-water load

Changes in drug levels with risk of adverse drug effects

Susceptibility to nocturia, if free water taken shortly before sleep

Liver

Hepatic mass

Hepatic blood flow

Activity of CYP 450 enzyme system

Changes in drug levels

Nose

Smell

Mucosal thinning or capillary fragility

Taste and consequent appetite

Likelihood (slightly) of nosebleeds

Peripheral nervous system

Baroreflex responses

Beta-adrenergic responsiveness and number of receptors

Signal transduction

Muscarinic parasympathetic responses

Preserved alpha-adrenergic responses

Susceptibility to syncope

Response to beta-blockers

Exaggerated response to anticholinergic drugs

Pulmonary system

Vital capacity

Lung elasticity (compliance)

Residual volume

FEV1

V/Q mismatch

Likelihood of shortness of breath during vigorous exercise if people are normally sedentary or if exercise is done at high altitudes

Risk of death due to pneumonia

Risk of serious complications (eg, respiratory failure) for patients with a pulmonary disorder

Vasculature

Endothelin-dependent vasodilation

Peripheral resistance

Susceptibility to hypertension

=decreased; = increased; FEV1= forced expiratory volume in 1 sec; V/Q =ventilation/perfusion.

Adapted from the Institute of Medicine: Pharmacokinetics and Drug Interactions in the Elderly Workshop. Washington DC, National Academy Press, 1997, pp. 8–9.

The unmodifiable effects of aging may be less dramatic than thought, and healthier, more vigorous aging may be possible for many people. Today, people > 65 are in better health than their ancestors and remain healthier longer.

Exercise in Older Adults

Exercise is usually used to mean movement that generates aerobic debt and increased heart rate and for many people is an important behavior with many positive outcomes. However, simple physical activity (eg, walking, gardening) has many of the same benefits for older people, especially those > 70; thus, physical activity, without aerobic debt or cardioacceleration, is recommended, even for those with mobility limitations.

All older patients starting an exercise program should be screened (by interview or questionnaire) to identify those with chronic disorders and to determine appropriate activities; however, virtually anyone can begin brief periods of walking, increased to 30 minutes 5 times a week. Physical activity is inappropriate for only a few older people (eg, those with unstable medical conditions). Whether those with chronic disorders need a complete medical examination before starting an activity depends on the results of tests that have already been done and on clinical judgment. Some experts recommend such an examination, possibly with an exercise stress test, for patients who have 2 cardiac risk factors (eg, hypertension, obesity) and who plan on starting an activity more strenuous than walking.

Exercise programs that are more strenuous than walking may include any combination of 4 types of exercise: endurance, muscle strengthening, balance training (eg, tai chi), and flexibility. The combination of exercises recommended depends on the patient’s medical condition and fitness level. For example, a seated exercise program that uses cuff weights for strength training and repeated movements for endurance training may be useful for patients who have difficulty standing and walking. An aquatics exercise program may be suggested for patients with arthritis. Patients should be able to select activities they enjoy but should be encouraged to include all 4 types of exercise. Of all types of exercise, endurance exercises (eg, walking, cycling, dancing, swimming, low-impact aerobics) have the most well-documented health benefits for older adults.

Some patients, particularly those with a heart disorder (eg, angina, 2 myocardial infarctions), require medical supervision during exercise.

High-intensity muscle-strengthening programs are particularly appropriate for frail older patients with sarcopenia. For these patients, machines that use air pressure rather than weights are useful because the resistance can be set lower and changed in smaller increments. High-intensity programs are safe even for nursing home residents > 80 in whom strength and mobility can be substantially improved. However, these programs are time-consuming because participants usually require close supervision.

Drugs and exercise

Doses of insulin and oral hypoglycemics in diabetics may need to be adjusted according to the amount of anticipated exercise to prevent hypoglycemia during exercise.

Doses of drugs that can cause orthostatic hypotension (eg, antidepressants, antihypertensives, hypnotics, anxiolytics, diuretics) may need to be lowered to avoid exacerbation of orthostasis by fluid loss during exercise. For patients taking such drugs, adequate fluid intake is essential during exercise.

Some sedative-hypnotics may reduce physical performance by reducing activity levels or by inhibiting muscles and nerves. These and other psychoactive drugs increase the risk of falls. Stopping such drugs or reducing their dose may be necessary to make exercise safe and to help patients adhere to their exercise regimen.

Reference

  • 1. de Souto Barreto P, Rolland Y, Vellas B, et al: Association of long-term exercise training with risk of falls, fractures, hospitalizations, and mortality in older adults: a systematic review and meta-analysis. JAMA Intern Med.179(3):394-405, 2018. doi:10.1001/jamainternmed.2018.5406.

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