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 VO2 max), muscle strength, and glucose tolerance in healthy but sedentary older adults.
Fewer than 15% of older adults meet the aerobic and muscle-strengthening physical activity recommendations of the U.S. Department of Health and Human Services (HHS) Guidelines (). 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 (1)
Reduced mortality rates, even for people who smoke and people with obesity
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
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.
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 medication 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 heart failure with reduced ejection fraction |
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 medication 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 CYP450 enzyme system | Changes in medication 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 medications |
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, adults > 65 are in better health than their ancestors and remain healthier longer.
General reference
1. Department of Health and Human Services USA: Physical activity guidelines for Americans midcourse report: Implementation strategies for older adults. Accessed 3/9/24.
Exercise in Older Adults
Older adults should aim to incorporate the following categories of exercise:
Endurance (aerobic)
Strength training
Balance
Flexibility
For example, the CDC Physical Activity Guidelines for Americans recommend that adults ≥ 65 years get at least 150 minutes a week of moderate-intensity aerobic activity plus strengthening activities at least 2 days a week for substantial health benefits (1).
Aerobic activity should be at least moderate intensity (eg, brisk walking, water aerobics, riding a bike at a casual pace).
Strength training may include lifting weights, use of resistance bands, heavy gardening, and yoga. The specific regimen can be tailored based on medical conditions and fitness level. For example, a chair exercise program using light weights and full body movements may be suitable for those with mobility limitations. Water-based exercises are good for people with arthritis (and can also be used for aerobic exercise. High-intensity strength training is especially appropriate for frail patients prone to sarcopenia and weakness. If strength training is done through a full range of motion, many of the exercises improve flexibility, and the enhanced muscle strength improves joint stability and, consequently, balance.
Balance exercises (eg, tai chi, backward walking) are recommended for older adults at risk of falling.
Flexibility exercise involves stretching major muscle groups several times a week, ideally after exercising the muscles when the muscles are least resistant to being stretched (ie, warmed up). An example is the runner's stretch, which stretches the gastrocnemius muscles.
These exercise recommendations are safe and provide benefits for most older adults, including those with chronic conditions. In general, walking and other moderate-intensity endurance exercises have the best evidence for reducing risk of chronic disease. Regardless of program type, exercising can help older adults maintain their independence.
Consultation with a health professional is still recommended before significantly increasing physical activity levels. A health care professional should monitor people at high risk of cardiac disorders when they are exercising vigorously.
Medications and exercise
Doses of insulin and oral hypoglycemics in patients with diabetes may need to be adjusted according to the amount of anticipated exercise to prevent hypoglycemia during exercise.
Doses of medications that can cause orthostatic hypotension (eg, antidepressants, antihypertensives, hypnotics, anxiolytics, diuretics) may need to be lowered to avoid exacerbating orthostasis by fluid loss during exercise. For patients taking such medications, 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 medications or illicit drugs increase the risk of falls. Stopping such agents or reducing their dose may be necessary to make exercise safe and to help patients adhere to their exercise regimen.
General references
1. Department of Health and Human Services USA: Physical activity guidelines for Americans midcourse report: Implementation strategies for older adults. Accessed 3/9/24.
2. 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
