Physiology of Ageing - Community Medicine (Geriatrics)

1. Definition and Concepts

• Gerontology: Study of physical and psychological changes incident to old age
• Geriatrics (Clinical Gerontology): Care of the aged
• Social Gerontology: Study of social problems arising from an increasing aged population
• Experimental Gerontology: Research into the basic biological problems of ageing - its physiology, biochemistry, pathology and psychology
• Senescence: Expression used for the deterioration in vitality or lowering of biological efficiency that accompanies ageing
• Biological age vs Chronological age: These are not identical - a person's physiological reserve does not directly correspond to years lived

• Park's Textbook of Preventive and Social Medicine, p. 689

2. Physiological Changes Due to the Ageing Process

2A. Disabilities Incident to the Ageing Process (Park's Classification)

2B. Cardiovascular System

• Intima-media thickening (IMT): Carotid IMT shows a 2-3 fold increase between ages 20 and 90 years, even in the absence of atherosclerosis
• Arterial stiffness: Fraying of medial elastic fibres and increased collagen deposition in the tunica media reduces arterial distensibility
• Isolated systolic hypertension: Systolic BP rises progressively due to arterial stiffness; diastolic BP rises until the 6th decade then declines due to reduced elastic recoil. This creates widened pulse pressure - a potent independent predictor of cardiovascular events
• Pulse Wave Velocity (PWV): Increases 2-3 fold from young to old in normotensive subjects - a sensitive index of arterial stiffness

• Decreased endothelial nitric oxide (NO)-mediated vasodilation
• Contributes to ischaemic diseases of heart, brain (stroke, vascular cognitive impairment) and lower extremities

• Reduction in microvascular density ("microvascular rarefaction") in heart, skeletal muscle, and brain - contributes to tissue ischaemia
• Impaired angiogenic processes
• Disruption of blood-brain barrier - contributes to neurodegenerative disease

• Decreased sympathetic response to stress
• Reduced vascular compliance
• Impaired baroreceptor responses - leading to blood pressure lability and susceptibility to hypotension
• Ventricular, valvular, rhythm, and vascular changes collectively lower the threshold for development of heart failure

• Fuster and Hurst's The Heart, 15th Ed, p. (block 22)
• Park's, p. 690

2C. Musculoskeletal System

• Osteoporosis: Bones undergo decalcification, becoming fragile and prone to fracture. Fracture neck of femur is a very common geriatric problem
• Arthritis: Fibrositis, myositis, neuritis, gout, rheumatoid arthritis, osteoarthritis, spondylitis of spine
• These cause more discomfort and disability than any other chronic disease in the elderly
• Reduced height and bone volume with age due to continuous skeletal remodelling
• Park's, p. 690

2D. Respiratory System

• Emphysema: Progressive destruction of alveolar walls and loss of elastic recoil
• Chronic bronchitis, asthma: Of major importance in upper decades of life
• Reduced respiratory reserve and impaired gas exchange
• Increased chest wall rigidity due to calcification of costal cartilages
• Park's, p. 690

2E. Nervous System and Special Senses

• Cognitive changes: Impaired memory, rigidity of outlook and dislike of change
• Sensory decline: Failure of vision (cataract, glaucoma), nerve deafness, diminished proprioception
• Increased fall risk due to impaired balance and coordination
• Loss of neurons; reduced neurotransmitter synthesis and receptor sensitivity
• Park's, p. 691

2F. Metabolic and Endocrine Changes

• Diabetes mellitus: Faulty carbohydrate metabolism - approximately 75% of diabetics are over 50 years of age. It is a leading cause of death as the population grows older
• Reduced basal metabolic rate (BMR)
• Altered body composition: decreased lean muscle mass (sarcopenia), increased fat mass, redistributed adipose tissue
• Park's, p. 690

2G. Skin

• Epidermis: Density of keratinocytes and melanocytes declines - causing thinning and abnormal pigmentation
• Dermis: Elastic fibres disappear (causing wrinkling), significant decrease in collagen and ground substance
• Dermal-epidermal junction: Retraction of dermal papillae and rete ridges causes flattening
• Decreased capacity to retain moisture - causing dryness
• Langerhans cells (cell-mediated immunity) decrease - impaired immune surveillance
• Atrophy of subcutaneous fat; gravitational redistribution of fat pads
• Photoageing (extrinsic): UV radiation causes elastosis, DNA damage, disorganization of dermal elastic tissue fibres
• Scott-Brown's ORL Head & Neck Surgery

2H. Genitourinary System

• Prostate: Enlargement leading to dysuria, nocturia, frequency and urgency of micturition
• Reduced renal reserve (decreased GFR with age)
• Reduced reproductive capacity: cessation of menstruation in women (menopause around age 40-50), diminution of sexual activity in men
• Park's, p. 691

3. Problems Associated with Long-Term Illness in the Aged

• Park's, pp. 689-691

4. Psychological Problems of Ageing

1. Mental changes: Impaired memory, cognitive rigidity, dislike of change
2. Sexual adjustment: Between 40-50, cessation of reproduction in women; diminution of sexual activity in men; physical and emotional disturbances (irritability, jealousy, despondency)
3. Emotional disorders: Social maladjustment; failure to adapt to ageing can result in bitterness, inner withdrawal, depression, weariness of life, even suicide

• Park's, p. 691

5. Lifestyle Factors and Healthy Ageing

• Park's, pp. 691-692

6. Theories of Ageing (Experimental Gerontology)

7. Epidemiological and Social Medicine Perspective

• In 2019, there were an estimated 694 million old persons worldwide, 540 million in developing countries
• India's population aged 60+ is projected to rise from 8% (2010) to 19% by 2050 (323 million people)
• By 2030, nearly 45% of India's disease burden will be borne by older adults
• The ageing population creates a double burden in developing countries: both infectious and non-communicable diseases
• The community must help the aged fight the triple evils: poverty, loneliness, and ill-health
• Park's, pp. 689-690

8. Preventive Approach (Levels of Prevention in Geriatrics)

• Park's, p. 693 (Table 31)

Summary: Key Physiological Changes in Ageing

Cardiovascular   → Arterial stiffness, ↑ systolic BP, ↓ cardiac reserve, endothelial dysfunction
Respiratory      → ↓ Elastic recoil, emphysema, ↓ lung capacity
Musculoskeletal  → Osteoporosis, sarcopenia, arthritis
Nervous System   → ↓ Neurons, impaired memory, sensory loss
Metabolic        → ↓ BMR, impaired glucose tolerance, ↑ fat mass
Renal            → ↓ GFR, reduced concentrating ability
Skin             → Thinning, loss of elasticity, dryness, impaired wound healing
Immune           → Immunosenescence, ↓ T-cell function
Reproductive     → Menopause in women; reduced testosterone in men