AGCNS-BC Adult-Gerontology CNS Exam

Aging is a complex, multifactorial process characterized by progressive physiological changes that affect every organ system. Understanding these changes is essential for the Adult-Gerontology CNS to differentiate normal aging from pathological conditions, anticipate complications, and develop appropriate care plans.

Several theories attempt to explain the aging process. Biological theories include programmed theories and damage theories. Programmed theories suggest aging follows a biological timetable regulated by changes in gene expression. The programmed longevity theory proposes that aging results from sequential switching on and off of certain genes. Endocrine theory focuses on biological clocks acting through hormones to control the pace of aging. Immunological theory posits that the immune system is programmed to decline over time, leading to increased vulnerability to infectious disease and death.

Damage or error theories emphasize environmental assaults that gradually cause cumulative damage. The wear and tear theory suggests that cells and tissues simply wear out over time. The rate of living theory proposes that lifespan inversely correlates with metabolic rate. Cross-linking theory suggests that accumulated cross-linked proteins damage cells and tissues. Free radical theory attributes aging to accumulated oxidative damage from free radicals. Somatic DNA damage theory links aging to accumulated genetic mutations.

The cardiovascular system undergoes significant structural and functional changes with aging. The heart muscle thickens, particularly the left ventricular wall, as a compensatory response to increased vascular stiffness. Cardiac output decreases approximately 1% per year after age 30. Maximum heart rate declines, typically calculated as 220 minus age. The sinoatrial node loses pacemaker cells, increasing susceptibility to arrhythmias.

Vascular changes include arterial stiffening due to loss of elastin and increased collagen deposition. Baroreceptor sensitivity decreases, impairing blood pressure regulation and increasing risk for orthostatic hypotension. Systolic blood pressure tends to increase while diastolic pressure may decrease, widening pulse pressure. Valvular calcification and sclerosis become more common. These changes reduce cardiovascular reserve and ability to respond to physiological stressors.

Clinical implications include increased risk for hypertension, heart failure, atrial fibrillation, and coronary artery disease. The CNS must recognize that older adults may present atypically during cardiac events, with symptoms such as confusion, weakness, or dyspnea rather than classic chest pain.

Structural changes in the respiratory system include decreased chest wall compliance due to calcification of costal cartilage and kyphosis. Respiratory muscle strength declines. Lung elasticity decreases while residual volume increases. Alveolar surface area decreases by approximately 20% by age 70. Mucociliary clearance becomes less efficient.

Functional changes include decreased vital capacity, forced expiratory volume, and maximum voluntary ventilation. Gas exchange efficiency declines due to ventilation-perfusion mismatch. Cough reflex and laryngeal reflexes weaken, increasing aspiration risk. Immune defenses in the respiratory tract diminish.

These changes increase susceptibility to respiratory infections, particularly pneumonia. Older adults may not demonstrate typical fever or productive cough with pneumonia. The CNS must monitor for subtle signs such as confusion, tachypnea, or functional decline. Pulmonary reserve decreases, making older adults more vulnerable to respiratory failure during acute illness.

Kidney mass decreases by 25-30% between ages 30 and 80. Nephron number declines, and glomerular filtration rate decreases approximately 1 mL/min/year after age 40. Renal blood flow decreases by 10% per decade after age 30. Tubular function declines, affecting concentration and dilution capacity.

These changes impair drug excretion, necessitating dose adjustments for renally cleared medications. Serum creatinine may remain normal despite decreased GFR due to decreased muscle mass and creatinine production. The Cockcroft-Gault equation or CKD-EPI equation should be used to estimate renal function.

Fluid and electrolyte regulation becomes less efficient. Older adults have decreased ability to conserve sodium and concentrate urine, increasing dehydration risk. Thirst sensation diminishes. These factors predispose older adults to hyponatremia, hypernatremia, dehydration, and fluid overload.

Oral changes include decreased saliva production, tooth loss, and reduced taste and smell sensation. Esophageal motility decreases, and lower esophageal sphincter pressure may decline, increasing reflux risk. Gastric motility slows, and gastric acid production may decrease, affecting nutrient absorption and bacterial overgrowth.

Small intestine absorptive surface area decreases slightly. Lactase production declines, increasing lactose intolerance prevalence. Hepatic blood flow and liver mass decrease by 20-40%, affecting drug metabolism. Phase I hepatic metabolism declines more than phase II metabolism. Gallbladder contractility decreases, increasing gallstone risk.

Colonic motility decreases, predisposing to constipation. Rectal sensation diminishes, potentially contributing to fecal incontinence. The CNS must address nutritional concerns, medication dosing, and bowel function in older adults.

Sarcopenia, the age-related loss of muscle mass and strength, begins around age 30 and accelerates after age 60. Muscle mass decreases 3-8% per decade after age 30. Muscle fiber number and size decrease, particularly type II fast-twitch fibers. Strength declines approximately 1.5% per year after age 50.

Bone density peaks around age 30 and then declines. Women experience accelerated bone loss during menopause. Osteoporosis affects approximately 25% of women and 5% of men over age 65. Vertebral compression fractures and hip fractures increase significantly with age.

Joint cartilage thins and loses elasticity. Synovial fluid production decreases. Ligaments and tendons lose flexibility. Osteoarthritis prevalence increases dramatically with age, affecting over 80% of adults over age 75.

Brain weight decreases approximately 5% per decade after age 40. Cerebral blood flow decreases. Neurotransmitter synthesis and receptor sensitivity decline. White matter volume decreases more rapidly than gray matter. Ventricular enlargement occurs.

Cognitive processing speed slows. Working memory capacity decreases. Retrieval of information may take longer, though long-term memory remains relatively intact. Executive function may decline. However, crystallized intelligence, vocabulary, and accumulated knowledge remain stable or improve.

Sleep architecture changes with decreased REM sleep and slow-wave sleep. Sleep efficiency decreases, and sleep becomes more fragmented. Circadian rhythm changes often result in earlier bedtimes and wake times.

Peripheral nervous system changes include decreased nerve conduction velocity, reduced vibratory sensation, and diminished reflexes. Position sense may decline. These changes contribute to balance problems and fall risk.

Vision changes include presbyopia (decreased accommodation), lens yellowing and opacity (cataracts), decreased pupil size and light adaptation, and increased glare sensitivity. Visual acuity, contrast sensitivity, and peripheral vision decline. Age-related macular degeneration and glaucoma prevalence increase.

Hearing loss (presbycusis) affects approximately one-third of adults over age 65. High-frequency hearing loss is most common. Speech discrimination decreases, particularly in noisy environments. Cerumen impaction is common and treatable.

Taste and smell sensation decline, affecting appetite and nutritional intake. Touch and pain sensation may decrease, potentially masking symptoms of acute illness or injury.

Skin becomes thinner, loses elasticity, and becomes more fragile. Subcutaneous fat decreases. Dermal-epidermal junction flattens, increasing shear injury risk. Sebaceous and sweat gland function decline, causing dry skin and impaired thermoregulation. Wound healing slows. Skin immune function decreases.

These changes increase susceptibility to skin tears, pressure injuries, hypothermia, and hyperthermia. Sun damage accumulates, increasing skin cancer risk.

Glucose tolerance decreases due to decreased insulin sensitivity and delayed insulin secretion. Thyroid function remains relatively stable, though TSH may increase slightly with age. Growth hormone and IGF-1 levels decline. DHEA and DHEA-S decrease significantly. Melatonin production decreases, contributing to sleep disturbances.

Menopause in women results in estrogen and progesterone decline, causing vasomotor symptoms, urogenital atrophy, and accelerated bone loss. In men, testosterone declines gradually (andropause), affecting muscle mass, bone density, and sexual function.

Immunosenescence refers to age-related decline in immune function. Thymic involution results in decreased naive T-cell production. T-cell function and diversity decline. B-cell function decreases. Inflammatory cytokine production increases (inflammaging). Vaccine response diminishes.

These changes increase susceptibility to infections, malignancies, and autoimmune diseases. Older adults may present atypically during infections without fever or elevated white blood cell count.

Comprehensive geriatric assessment evaluates multiple domains including physical function, cognition, mood, nutrition, social support, and environment. Activities of daily living (ADLs) include bathing, dressing, toileting, transferring, continence, and feeding. Instrumental activities of daily living (IADLs) include medication management, finances, transportation, shopping, meal preparation, housekeeping, and telephone use.

Validated tools include the Katz Index for ADLs, Lawton Scale for IADLs, Timed Up and Go test for mobility, and Mini Nutritional Assessment for nutrition. Functional assessment identifies areas for intervention and helps establish realistic goals.