Senile (Age-Related) Changes - A System-by-System Overview

Quantitative Benchmarks at Age 80

1. Nervous System (Gerontologic Neurology)

• Brain weight falls 10-15% by age 80
• Cerebral blood flow decreases by ~20%
• Loss of neurons (especially in cortex, cerebellum, and substantia nigra), with gyral thinning and sulcal widening
• Accumulation of lipofuscin ("wear-and-tear" pigment) in surviving neurons
• A scattering of senile plaques (amyloid) and neurofibrillary tangles can appear in normal aging - but in far smaller numbers than in Alzheimer's disease
• Expansion of the parasagittal dural space (seen on MRI), reflecting changes in CSF dynamics and glymphatic function

• Progressive pupillary constriction (miosis)
• Decreased light reactions
• Presbyopia - loss of accommodation (lens hardening)
• Insufficiency of convergence
• Restricted upward conjugate gaze
• Diminished dark adaptation; increased glare sensitivity

• Presbycusis - progressive high-frequency hearing loss, with loss of hair cells in the organ of Corti and consequent decline in speech discrimination
• Diminished smell (anosmia) and to a lesser degree taste (64% fewer taste buds by age 80)

• Reduced motor speed, agility, fine coordination
• Slowed reaction time
• Sarcopenia - loss of muscle mass, especially legs, proximal muscles, dorsal interossei, thenar, and anterior tibial muscles
• Progressive loss of anterior horn cells contributes to denervation atrophy; denervation atrophy of the gastrocnemius is found in 80% of people over 70
• Lost muscle fibers are replaced by endomysial connective tissue and fat

• Ankle reflexes diminished in those over 70; Achilles reflexes lost in those over 80
• "Cortical release" signs (snout, palmomental) appear in up to 50% of normal people over 60

• "Senile gait" - decreased stride length, reduced hip excursion, less toe elevation, stooped posture, slower cadence, widened base for stability
• Adams and Victor's Principles of Neurology, 12th Ed.

2. Skin (Dermatogerontology)

• Epidermis thins, rete ridges flatten
• Decreased collagen and elastin fiber count
• Pallor, fine wrinkles, xerosis (dry skin), decreased elasticity, fragility
• Weakened antioxidant defenses lead to oxidative stress and cellular senescence
• Telomere shortening with each somatic division eventually triggers cell-cycle arrest

• UVA and UVB cause DNA damage, MMP activation, collagen degradation, and elastotic material accumulation (solar elastosis)
• Features: deep coarse wrinkles, mottled pigmentation, telangiectases, laxity, fragility, dyspigmentation

• Solar lentigines ("age spots")
• Seborrheic keratoses
• Senile angiomas (cherry angiomas)
• Xerosis and asteatotic eczema
• Pruritus
• Increased risk of both benign and malignant growths

• Fitzpatrick's Dermatology, Vol. 1-2

3. Respiratory System

• Ciliary motility decreases significantly with age, impairing mucociliary clearance and increasing susceptibility to lower respiratory infections

• After age 30-40, respiratory bronchioles and alveolar ducts progressively enlarge ("ductectasia")
• Alveolar septa shorten; mean linear intercept (distance between alveolar walls) increases
• Alveolar surface area decreases by ~15% by age 70
• Surface-to-volume ratio falls
• These changes were historically called "senile emphysema" - but unlike true emphysema, there is NO destruction of alveolar septa with fusion of airspaces. The NHLBI recommends using the term "aging lung" instead and retiring "senile emphysema"

• Max breathing capacity: -44% by age 80
• Max ventilatory volume: -47% by age 80
• Max O2 utilization with exercise: -60% by age 80
• Fishman's Pulmonary Diseases and Disorders

4. Cardiovascular System

• Cardiac output at rest falls ~35% by age 80
• Decreased sympathetic response to stress
• Reduced vascular compliance (arteries stiffen)
• Impaired baroreceptor responses - predisposes to orthostatic hypotension and perioperative blood pressure lability
• Increased prevalence of coronary artery disease, hypertension, atrial fibrillation
• Left ventricular hypertrophy from chronic pressure overload; diastolic dysfunction is common
• These changes place elderly patients at significantly higher perioperative cardiac risk (POISE-2 trial: age >75 was an independent risk factor for postoperative MI, HR 1.89)
• Barash's Clinical Anesthesia, 9th Ed.

5. Musculoskeletal System

• Occurs in both sexes with advanced age (distinct from postmenopausal/Type I osteoporosis)
• Classified as "low-turnover" osteoporosis - reduced physical activity, declining sex hormones, and impaired calcium absorption all contribute
• Reduced bone mass increases fracture risk, especially hip and vertebral fractures
• Decreased physical activity compounds the problem as osteocytes respond to mechanical loading

• Age-related loss of skeletal muscle mass and strength
• Due to combined denervation (loss of motor neurons), disuse, and hormonal changes
• Robbins & Cotran Pathologic Basis of Disease

6. Renal System

• Number of glomeruli falls by ~44% by age 80
• GFR declines by ~31% by age 80
• Reduced renal reserve means drugs cleared renally (e.g., aminoglycosides, NSAIDs, digoxin) require dose adjustment
• Diminished ability to concentrate urine and handle volume/electrolyte stress

7. ENT - Senile Rhinitis

• Aging nose shows decreased nasal blood flow and diminished humidification
• Predisposes to rhinitis in elderly; termed "senile rhinitis" in otolaryngology literature
• Cummings Otolaryngology

8. Pharmacologic Implications

• Altered volume of distribution (less body water, more fat)
• Reduced cardiac output delays IV drug onset
• Impaired renal/hepatic clearance prolongs drug half-lives
• Reduced protein binding increases free drug fraction
• Elderly patients are highly susceptible to adverse drug reactions and polypharmacy interactions
• Goodman & Gilman's Pharmacological Basis of Therapeutics

Named "Senile" Conditions in Medicine