Physical Changes With Aging

By Richard W. Besdine, MD, The Warren Alpert Medical School of Brown University

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Approach to the Geriatric Patient
Introduction to Geriatrics
Physical Changes With Aging
Evaluation of the Elderly Patient
Unusual Presentations of Illness in the Elderly

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 (O₂consumption per unit time, or Vo₂max), muscle strength, and glucose tolerance in healthy but sedentary older people (see Exercise).

Only about 10% of the elderly participate in regular physical activity for > 30 min 5 times/wk (a common recommendation). About 35 to 45% participate in minimal activity. The elderly 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 the elderly 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 MI), 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
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.

Exercise

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 elderly 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 min 5 times/wk. Physical activity is inappropriate for only a few elderly 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 the elderly. Some patients, particularly those with a heart disorder (eg, angina, ≥ 2 MIs), require medical supervision during exercise. High-intensity muscle-strengthening programs are particularly appropriate for frail elderly 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.

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 elderly 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 min 5 times/wk. Physical activity is inappropriate for only a few elderly 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 the elderly.

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

High-intensity muscle-strengthening programs are particularly appropriate for frail elderly 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.

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.

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 Tendency toward 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 parkinsonian symptoms (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 Tendency toward 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	Tendency toward 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	Tendency toward syncope ↓ Ejection fraction ↑ Rates of atrial fibrillation ↑ Rates of diastolic dysfunction and diastolic heart failure
Immune system	↓ T-cell function ↓ B-cell function	Increased 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 Tendency toward 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 Tendency toward dehydration
Liver	↓ Hepatic mass ↓ Hepatic blood flow ↓ Activity of CYP 450 enzyme system	Changes in drug levels
Nose	↓ Smell	↓ 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	Tendency toward 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	Tendency toward 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.