PHYSIOLOGIC CHANGES AND DISEASE PROCESSES OF AGING

Aging involves changes in physiology. Some changes result in declines in function of the senses and activities of daily life and increases in susceptibility to and frequency of disease or disability. Aging is a major risk factor for a number of chronic diseases, and many diseases appear to accelerate the aging process, manifesting in declines in function and quality of life (NIA, 2020; Kane et al., 2018).

Musculoskeletal System

Musculoskeletal disorders that are common among older patients include the triad of loss of muscle mass and function, tendinopathies, and arthritis. Their common trait is progressive loss of neuromuscular performance with a risk of adverse outcomes, including pain, mobility disorders, increased risk of falls and fractures, and disability or impaired ability to perform activities of daily living.

Bone mass decreases in healthy older people, and age-related changes in women are compounded by menopausal changes in bone mass and function. Osteoporosis due to vitamin D deficiency, common in older people, increases risk for bone fracture and slows rate of bone repair.

The vertebrae lose mineral content, making bones thinner, and vertebral discs lose fluid and thin. The spinal column curves and compresses, and overall height decreases. Posture becomes stooped, and postural hyperkyphosis (excessive curve of the spine) may occur. Shoulders may narrow, pelvis widen, knees and hips become more flexed, and neck tilt backward (LibreTexts, 2020).

With aging, muscle mass decreases in relation to body weight in both men and women, greater in the legs than arms. Lost muscle tissue may be replaced with tough, fibrous tissue. Loss of muscle is associated with decreased strength and slowed and limited movements, and contributes to age-related insulin resistance as well as changes in body composition and distribution for water-soluble drugs.

Tendons begin to shrink, lose mass, and contain less water, causing stiffness and decreased stress tolerance. Ligaments shorten and lose flexibility. Joint changes include inflammation, stiffness, deformity, and pain, leading to functional disability.

Gait becomes slower and shorter. Walking becomes unsteady, with less arm swinging and increased risk for injury from falls (NIH, 2020a).

Foot problems such as bunions are common and may interfere with functioning and daily activities (Besdine, 2019).

Common management strategies for musculoskeletal disorders include physical exercise, either alone or in combination with nutritional intervention. High-intensity resistance training can improve strength and mass of skeletal muscles and may counteract age-related decline in muscle size and function. A balanced program of both endurance and strength exercises performed on a regular schedule is usually recommended. Nutritional supplements may be advised, including vitamin D.

Interventions for managing arthritis may include physical modalities such as heat and cold, techniques to manage or control edema and inflammation, therapeutic activities and exercises, and provision of custom or prefabricated orthotic devices.

Most older adults can benefit from targeted programs to prevent falls and optimize bone health (Minetto et al., 2020).

Integumentary System

Skin changes are the most visible signs of aging. Growths such as skin tags, warts, rough patches (keratoses), and other blemishes are more common in older adults. More than 90% of all older people also have some type of skin disorder, such as xerosis, pruritus, eczematous dermatitis, and purpura (NIH, 2020b).

Decreased concentration of 7-dehydrocholesterol in the epidermis results in decreased synthesis of vitamin D necessary for bone health.

Ability to sense touch, pressure, vibration, heat, and cold may decrease.

Wound healing slows, and moisture retention decreases. Body hair decreases, and there is less sebum and cerumen, resulting in dryness and itchiness.

Blood vessels become fragile, leading to bruising and bleeding under the skin. Reduced sweating can lead to heat intolerance.

The subcutaneous layer thins and provides less insulation and padding, increasing risk of skin injury and reduced body temperature maintenance. Pressure injuries become more common.

Nails grow more slowly and thicken, and ingrown toenails become more common (NIH, 2020b).

Health maintenance for skin integrity in the older adult is essential and requires a holistic and interdisciplinary approach. Skin basics include:

• Educating patients and caregivers
• Performing regular skin assessments
• Maintaining mobility
• Relieving pressure
• Using safe manual handling techniques
• Providing skin care, paying attention to high-risk areas
• Encouraging good nutrition and hydration

Older patients and caregivers should be encouraged to inspect feet daily for skin color, dryness, swelling or tenderness, blisters, cracks, sores, ulcers, corns, ingrown toenails, paresthesia, or pain. Other common foot problems in older individuals include calluses, foot deformity, fungal infection, and warts. A podiatry consult may be recommended (Fraser, 2020; EHS, 2018).

Because many older adults had chicken pox as children, they are at risk for reactivation of the varicella zoster virus, which causes shingles, and should obtain a vaccine if there are no contraindications (Fraser, 2020; MSKL, 2020).

Cardiovascular System

Cardiac aging is associated with left ventricular hypertrophy, fibrosis, and diastolic dysfunction, resulting in reduced cardiac output. These changes result in reduced left ventricular filling, which can lead to heart failure, especially in older people with other diseases such as hypertension, obesity, and diabetes.

The walls of the arteries and arterioles also become harder and thicker (arteriosclerosis), and less elastic, affecting the ability of blood pressure to make adjustments when standing quickly, putting people at risk for dizziness or fainting. And because blood vessels become less elastic with age, they do not relax quickly, causing blood pressure to increase during systole (Gupta & Shea, 2019; Fajemiroye et al., 2018).

Approximately 80% of deaths attributed to acute coronary syndromes occur in patients 65 years of age and older. The prevalence and complexity of cardiac arrhythmias increase with age, the most common sustained dysrhythmia being atrial fibrillation. Older adults are also at increased risk of major complications from therapeutic interventions. The prevalence of peripheral arterial disease increases progressively with age and is often predictive of the presence of coronary artery and cerebrovascular disease (Kyriazis & Saridi, 2020; Harper et al., 2019).

Management and prevention of cardiovascular issues in the older adult include patient education regarding modifying controllable risk factors such as diabetes, hypertension, overweight, diet, exercise, smoking, and alcohol intake. This includes instruction on signs and symptoms of acute myocardial infarction; routine exercise; and nutrition, such as low-fat, low-cholesterol, and low-sodium diets.

Hypertension management also requires lifestyle changes and pharmaceutical therapy, often started at a low level and increased, if indicated. Education on stress management and encouragement of some form of relaxation technique are also recommended.

The goal of therapy for atrial fibrillation is the prevention of thromboembolism, which is often managed with anticoagulation therapy, such as warfarin (Coumadin) or apixaban (Eliquis).

Management of peripheral vascular disease includes general prevention measures such as avoiding prolonged standing or sitting, exercising on a regular basis, and other lifestyle recommendations. Pharmaceutical therapy includes antiplatelet or anticlotting agents, statins, and medications that increase blood supply. Nonpharmaceutical therapy includes extremity elevation, compression stockings, exercise, and wound care for ulcerations caused by chronic venous insufficiency (Cash & Glass, 2019).

Urinary System Changes

KIDNEYS

With aging, the volume of kidney tissue decreases. Over an average lifespan, nephrons are reduced by half, and by age 75 atherosclerosis of renal arteries reduces renal blood flow by half. Glomerular filtration rate and maximum excretory capacity are reduced by the same proportion.

The kidneys can still maintain normal homeostatic mechanisms and waste disposal within limits, but they are less efficient and need more time, and their reserves may be minimal. Therefore, relatively minor degrees of dehydration, infection, or impaired cardiac output may lead to kidney failure. Loss of renal reserve increases the risk for toxic accumulation of renally cleared medications.

The kidneys have a central role in maintaining normal levels of most electrolytes. Reduced diluting capacity of the kidney increases the risk of hyponatremia in older patients, particularly those on a low-protein diet (Physiopedia, 2021).

The kidneys play a role in glucose homeostasis. Under normal circumstances, the kidneys filter and reabsorb 100% of glucose. In addition, they produce glucose by gluconeogenesis, contributing 20% to 25% of circulating glucose (Bhimma, 2018).

Diabetes mellitus is the most common cause of chronic kidney disease. Hyperglycemia damages the glomeruli within each kidney, resulting in an increased glomerular filtration rate.

Kidney disease leads to a decline in production of erythropoietin, which is one of the causes of unexplained anemia in older adults. Most people with kidney disease will develop anemia (NKF, 2020; Artz, 2019).

There is no cure for chronic kidney disease, and once the kidneys are damaged, they cannot be repaired. If and when the kidneys fail, renal dialysis is required.

Prevention of chronic kidney disease involves lowering the risk by making healthy lifestyle changes, maintaining a normal blood pressure, and controlling diabetes (CDC, 2020a).

BLADDER AND URETHRA

Aging increases bladder dysfunction, including reduction in bladder capacity, uninhibited contractions, and decreased urinary flow rate. Urinary tract infections common in older people have more systemic effects. They are commonly seen in older adults admitted to the hospital because of a fall or acute confusion.

The urethra can become blocked. In women this can be due to weakened muscles caused by bladder or vaginal prolapse, and in men by an enlarged prostate gland (Physiopedia, 2021).

Urinary incontinence is a significant health problem for older adults, both physically and psychologically. Women are disproportionately affected. Common age-related physiologic changes predisposing to incontinence include decreased bladder capacity, benign prostatic hyperplasia (BPH) in men, and menopausal loss of estrogen in women. Other risk factors for incontinence include immobility, certain types of medications, obesity, smoking, malnutrition, delirium, depression, sensory impairment, and environmental barriers (NIH, 2020c; Dowling-Castronov & Spiro, 2020).

Patients presenting with symptoms of urinary tract infection should be placed on an appropriate antibiotic.

Urinary retention is most commonly caused by BPH, whose main treatments include:

• Active surveillance by a urologist
• Medications
• Less invasive procedures, such as a prostatic urethral lift (PUL), water vapor thermal therapy, and transurethral microwave therapy (TUMT) that destroys prostate cells; and catheterization, intermittent or indwelling
• Invasive surgical procedures, including transurethral resection of the prostate (TURP)
  (AUA, 2020)

Management of urinary incontinence depends on the type of incontinence, severity, and underlying cause, and a combination of treatments may be used (see table).

INTERVENTIONS FOR URINARY INCONTINENCE

Type	Interventions
(Mayo Clinic, 2019; Cunningham & Valasak, 2019)
Lifestyle changes	Weight loss Smoking cessation Alcohol avoidance Decreased caffeine intake Prevention of constipation Avoiding heavy lifting
Behavioral techniques	Scheduled or delayed timed urination Double voiding
Physical therapy	Pelvic floor exercises (e.g., Kegel’s) Muscle-strengthening exercises Electrical stimulation Biofeedback
Occupational therapy	Bladder retraining Modifications to food and fluids Relaxation techniques Support for integration of training
Medications	Anticholinergics Alpha blockers for men Topical estrogen for women
Medical devices	Vaginal rings and urethral inserts
Surgery	Single sling procedures Bladder neck suspension Prolapse surgery Artificial urinary sphincter implants
Supportive interventions and devices	Absorbent pads Protective undergarments, modified clothing Intermittent catheterization Condom catheter for men Urethral plugs and penile clamps

Respiratory System

Aging of the respiratory system reduces the capacity of all pulmonary functions, which may lead to decompensation when the system is stressed.

The effects of aging in other areas of the body also affect the lungs. These include changes in the bones and muscles of the chest and spine. Bones become thinner and change shape and can alter the shape of the ribcage, resulting in decreased expansion and contraction. The diaphragm becomes weakened, impairing both inhalation and exhalation. These changes may lower the oxygen level in the body and raise carbon dioxide levels, resulting in tiredness and shortness of breath.

Aging also causes the walls of the alveoli to deteriorate, lose shape, and become baggy. Dead space increases with age as larger airways increase in diameter.

The nervous system, which monitors respiratory volume and blood gas levels and regulates respiratory rate, may lose some of its function. Breathing may become more difficult and gas exchange impaired. Dysphagia or impaired esophageal motility, also common in old age, may exacerbate the tendency to aspirate.

Decline in effectiveness of the immune system means the body is less able to fight lung infections and less able to recover following exposure to smoke or other harmful substances (NIH, 2020d).

Normal aging results in a number of changes to the structure and function of the respiratory system.

Because older people are at highest risk of developing pneumonia, influenza and pneumococcal pneumonia vaccines are highly recommended.

Common respiratory diseases experienced by older persons include chronic obstructive pulmonary disease (COPD) and emphysema. There is a greater prevalence of COPD in older adults as a result of smoking. Management can be difficult because of those coexisting medical problems, requiring geriatric care and attention from a team of providers.

Risk for COPD and emphysema can be reduced through lifestyle management that includes encouraging older adults to stop smoking, avoid air pollution, and reduce weight to improve diaphragm function. Pulmonary function does not respond to exercise training, however; aging, therefore, may become an increasingly important limiting factor for physical activity (NIH, 2020d).

COPD affects the well-being of the older adult both physically and socially, increasing disability and dependency. The main treatment for COPD is inhaled medications, including steroids. Impact of using long-term inhaled steroids must be considered in this population. Therapies that have a proven impact on mortality include smoking cessation and oxygen therapy (Gill, 2017).

Emphysema, a form of COPD, can be treated with the Zephyr valve, a one-way valve placed in three to five airways that reduces hyperinflation of a portion of the lung (Dransfield et al., 2020).

Endocrine System

The endocrine system consists of organs and tissues that produce hormones that control the function of target organs. Aging results in changes in the way body systems are controlled, with some target tissues becoming less sensitive to their controlling hormones. Also, the amounts of hormone production may change. Many of the organs that produce hormones are controlled by other hormones, and aging also changes this process (van den Beld et al., 2018).

The thyroid gland produces hormones that help control metabolism, and with aging, metabolism slows. There is an increased risk of hypothyroidism with aging, which may increase the subsequent risk of death due to cardiovascular disease.

Parathyroid gland hormone affects calcium and phosphate levels. This hormone’s level rises with age, contributing to osteoporosis, leading to kidney stones and renal failure, and significantly decreasing the quality of life.

Insulin is produced by the beta cells in the pancreas, and after age 50, cells become less and less sensitive to its effects. An increase in fibrosis and fatty deposits increases glucose intolerance and decreases sensitivity to insulin. Type 2 diabetes is the most common type of diabetes among this age group and is on the rise due to increasing obesity and failure to remain physically active, both of which contribute to insulin resistance.

Normal aging results in changes in adrenal secretion of both ACTH and cortisol, most significantly an increase in cortisol levels, which can have serious consequences in the integrity of both the structure and function of various areas in the brain, leading to impairment in normal memory, cognitive function, and sleep cycles.

Melatonin is a hormone secreted by the pineal gland in response to darkness. A decline in melatonin level is believed to play a role in the loss of normal sleep-wake cycles with aging (NIH, 2020e).

Gonads begin to secrete less estrogen in females and less testosterone in males, increasing the risk for atherosclerosis and osteoporosis in both genders. Less estrogen leads to menopause, the decline of ovarian function, and changes in the uterus and vaginal tissues that may interfere with sexual satisfaction. For males, reduction in levels of testosterone occurs gradually during andropause. This decline in hormone may increase the risk of sexual dysfunction; however, age does not predict male fertility (Morley, 2019; NIH, 2020f).

Among other medical issues, older adults with the diagnosis of HIV/AIDS may develop endocrine problems specific to HIV infection and its treatment. These may include gonadal dysfunction, osteoporosis with increased fracture risk, and dyslipidemia with increased cardiovascular risk (Zaid & Greenman, 2019).

MANAGEMENT AND PREVENTION

Treatment of endocrine disorders can be complicated, as changing one hormone level can affect another. Management takes into account coexisting medical illness, medications, alterations in clearance rate of hormones, and changes in target organ sensitivity with older age.

Hyperthyroidism and Hypothyroidism

Patients with hyperthyroidism may be started on antithyroid medications such as methimazole or beta blockers to help control symptoms. For those with hypothyroidism, thyroid replacement medication such as levothyroxine may be started (Cleveland Clinic, 2020).

Diabetes Mellitus

For patients with diabetes, guidelines stress the importance of considering overall health, comorbidities, cognitive and physical status, hypoglycemia risk, and life expectancy to guide glycemic goal setting. Lifestyle modification is important, including diet and exercise, and when such modifications alone are unable to maintain target treatment goals, antihyperglycemic pharmaceutical agents are considered (Leung et al., 2018).

Hyperparathyroidism

Hyperparathyroidism, the most common cause of hypercalcemia, increases with age. Surgical treatment substantially improves quality of life and is more cost-effective than medical management (Dombrowsky et al., 2018).

Excess Adrenal Cortisol Secretion

Management of excess adrenal secretion of cortisol involves recommending participation in physical activity that improves physical performance in order to attenuate the negative impact of chronic stress and normalize adrenal secretion of cortisol (Tortosa-Martinez et al., 2018).

Menopause and Andropause

With the decline in sex hormones, both men and women face organic changes that can affect sexual functioning. For women it may include vaginal dryness, irritation/itching, inadequate lubrication, and dyspareunia (painful intercourse). For men, erectile dysfunction prevalence increases with age, and some men develop testosterone deficiency that can severely reduce libido.

Recommended treatments for the symptoms of menopause include vaginal moisturizers and lubricants, vaginal estrogens, and oral or transdermal hormone therapy.

The best way to manage and prevent erectile dysfunction (ED) is to make healthy lifestyle choices, manage any existing chronic health conditions, and be screened for depression or other possible psychological causes of ED. Exercise, especially moderate to vigorous aerobic activity, has been found to improve ED. Other treatments may include oral, rectal, or injected drugs; testosterone replacement; penis pumps; and penile implants.

Testosterone replacement for men can be recommended as long as maintenance of fertility is not desired. Testosterone replacement can restore lean body mass, physical strength, erectile function, and libido as well as improve mood, bone mineral density, and quality of life (Jannini & Nappi, 2018; Mayo Clinic, 2020a).

Gastrointestinal System

Age-related changes in the digestive system begin in the mouth and can affect virtually all aspects of the digestive system.

Contractions of the esophagus and tensions in the upper esophageal sphincter decreases, and some older adults can be affected by diseases or disorders that interfere with esophageal contractions.

The stomach lining’s capacity to resist damage decreases, which in turn may increase risk of peptic ulcer disease, especially in those who use aspirin or NSAIDs.

Minor changes occur in the structure of the small intestine. Lactase levels decrease, leading to intolerance of dairy products by many older adults. Excessive growth of certain bacteria becomes more common with age and can lead to pain, bloating, and weight loss. This may also lead to decreased absorption of certain nutrients, such as vitamin B₁₂, iron, and calcium.

The rectum enlarges somewhat, and constipation becomes more common related to a slight slowing in movements of contents through the large intestine, a modest decrease in contractions of the rectum when filled with stool, frequent use of drugs that can cause constipation, and less exercise or physical activity.

The number of secretory cells in the pancreas decreases with age, resulting in a decrease in the level of fat digestion. The liver reduces in size, and metabolism of many substances decreases. This is important when considering medications whose dosages often need to be decreased in older people. Production and flow of bile decreases, and as a result, gallstones are more common (Ruiz, 2020).

Management and prevention require ensuring that only those medications the patient needs are being taken. Lifestyle modifications such as staying active and managing weight can reduce the number of medications needed, thus avoiding digestive side effects. Staying well hydrated and increasing fiber can help reduce complaints related to constipation (Cleveland Clinic, 2021).

Sensory Changes

Sensory changes in later life affect how people perceive and experience the world and can have an enormous impact on independence, safety, and quality of life. All five senses (vision, hearing, taste, smell, and touch) diminish in acuity with age. Aging raises the threshold of the amount of stimulation necessary to become aware of a sensation, with stimulation required. Sensory changes can affect lifestyle by causing difficulties with communication, enjoyment of activities, and staying involved with others, which can then lead to isolation (NIH, 2020g).

Eyes become less able to tolerate glare, and problems with glare, brightness, and darkness may lead to impaired night vision and reduced color discrimination. Visual acuity gradually declines, causing difficulty focusing on close-up objects (presbyopia). Common eye disorders affecting older adults include cataracts, glaucoma, retinopathies and age-related macular degeneration (AMD), the leading cause of severe and permanent vision loss in older adults (NIH, 2020g).

Aging results in changes in the structures inside the ear, causing a decline in function and causing a major impact on independence, safety, and quality of life. With aging, the ability of the ear to pick up sounds decreases, and problems with maintaining balance may also occur.

It is important to remind older patients to follow the recommendation of the American Academy of Ophthalmology for a comprehensive vision exam every year or every other year, which can assure that the patient has the proper eyeglass or contact lens prescription and to check for common eye disorders (Boyd, 2020).

Preventing hearing loss involves management of hypertension and diabetes; smoking cessation; limiting alcohol use; avoiding ototoxic drugs whenever possible; eating foods high in vitamins A, C, E, and especially B₁₂; and wearing hearing protection in noisy environments. When hearing loss does occur in older adults, it is usually permanent, and it can be managed using adaptive techniques and assistive devices (NIH, 2020g).

Nutrition

Obesity is the most common nutritional disorder in the older adult living in the community, and malnutrition is most common in those in acute and long-term care facilities.

Malnutrition in older adults can lead to various health problems, including:

• A weak immune system, which increases the risk of infections
• Poor wound healing
• Muscle weakness and decreased bone mass, which can lead to falls and fractures
• A higher risk of hospitalization and risk of death
  (Mayo Clinic, 2020b)

Interventions for patients who are malnourished are directed at the underlying cause as well as dietary modification. Nutritional restrictions are lifted for patients with diabetes who may do well with a regular diet and adequate monitoring. High-calorie foods are recommended. Oral nutritional supplementation for patients who do not regain weight are also recommended, with adjustments in meal preparation and diet.

Advice regarding weight loss in the overweight older person is tailored to the individual, assessing the impact of excess weight on quality of life and the need for regular exercise. It is not recommended that people over the age of 80 who are slightly obese be placed on calorie-restricted diets. The best option is to eat at least three meals a day that provide 30 grams of protein each, and to engage in two or three weekly sessions of resistance training that taxes all the large muscle groups in order to preserve muscle mass (Ritchie & Yukawa, 2020).