WEEK 12 AGEING

Adulthood Age Groups

• Adulthood spans from age 20 to death, marked by significant physical, cognitive, and psychosocial changes.

• Young adulthood: 20-40 years.

  • Focuses on career establishment entailing advanced education, job attainment, and professional growth, relationship building including forming intimate partnerships and starting families, and family.

• Middle age: 40-65 years.

  • Characterized by career consolidation involving achieving stability and expertise in chosen fields, family responsibilities such as raising children and caring for aging parents, and awareness of mortality prompting reflections on life achievements and future goals.

• Older adult: 65 years to death.

  • Involves retirement leading to adjustments in daily routines and social roles, health management requiring greater attention to chronic conditions and preventive care, and reflection on life including reviewing experiences, accomplishments, and legacies.

• Three generations within older adults:-

  • 65-75 years: Active retirement involving travel, volunteering, and lifelong learning, maintaining social connections through community involvement and social networks, and pursuing hobbies promoting mental and physical well-being.

  • 75-85 years: Increased focus on health and managing chronic conditions requiring medical appointments and lifestyle adjustments, potential need for supportive care services, and adapting living environments to accommodate mobility limitations.

  • 85+ years: Frailty characterized by decreased physical reserves and increased vulnerability, increased dependency requiring assistance with daily activities, and end-of-life care emphasizing comfort and dignity.

Definitions

• Ageing: The process of growing old, impacting various aspects of life.

  • Includes biological entailing cellular and molecular changes, psychological involving cognitive and emotional adjustments, and social changes affecting roles and relationships.

• Senescence: The process of deterioration with age, leading to functional decline.

  • Characterized by reduced physiological functions such as decreased organ efficiency and immune response, and increased vulnerability to disease making older adults more susceptible to illnesses and infections.

### Why Do We Age? Theories and Potential Causes

Cell Division and Chromosome Damage:

• Cells constantly divide to replace and build tissues, maintaining the body's structure and function.

• Chromosomes within these cells become damaged and deteriorate over time, affecting cellular health and functionality.

  • Telomeres shorten with each cell division, limiting the number of divisions a cell can undergo, eventually leading to cellular senescence.

• New cells are not as healthy or functional as the original cells, contributing to overall ageing.

- Accumulation of DNA damage and mutations affects cellular function, leading to cellular dysfunction and disease.

Free Radical Theory of Ageing:

• Free radicals can alter the structure of molecules, leading to damage and dysfunction, accelerating the ageing process.

  • Oxidative stress from free radicals damages lipids, proteins, and DNA, impairing cellular functions and causing inflammation.

- Antioxidants can neutralize free radicals, but their production declines with age, making the body more vulnerable to oxidative damage.

Decline of Mitochondrial DNA:

• Results in a decline in ATP production, affecting energy levels and cellular functions, leading to fatigue and reduced physical performance.

- Mutations in mitochondrial DNA accumulate over time, impairing mitochondrial function, contributing to energy deficits and cellular ageing.

Immune System Inefficiency:

• The immune system becomes less efficient with age, increasing susceptibility to illnesses, making older adults more prone to infections and autoimmune diseases.

- Immunosenescence leads to reduced T cell function and increased inflammation, impairing the body's ability to fight off pathogens and maintain health.

Genetic Traits:

• Genetic factors influence the rate and extent of ageing, determining individual longevity and disease susceptibility.

- Certain genes are associated with longevity and resistance to age-related diseases, offering potential targets for interventions to slow ageing.

Reduced Ability to Maintain Homeostasis:

• The body's ability to maintain a stable internal environment declines, affecting overall health and resilience.

  • Reduced ability to regulate blood pressure, temperature, and glucose levels, leading to increased risk of chronic diseases.

Causes of Ageing

• Ageing is a complex and multifactorial process, influenced by various intrinsic and extrinsic factors.

  • Involves the interaction of genetic, environmental, and lifestyle factors, shaping the ageing trajectory.

### Three Stages of Ageing

Basic Homeostasis:

• Maintaining stable body temperature and pH levels, essential for survival and well-being.

- Becomes challenging due to reduced physiological reserves, making older adults more vulnerable to environmental stressors.

Decrease in Organ Mass:

• Organs may shrink or lose tissue mass, affecting their functional capacity.

- Sarcopenia (loss of muscle mass) is a common age-related change, leading to reduced strength, mobility, and metabolic rate.

Decline in Function:

• Organs and systems become less efficient, affecting overall physiological performance.

- Reduced cardiac output, lung capacity, and kidney function, increasing the risk of cardiovascular, respiratory, and renal diseases.

Behavioral Adaptations

### Ageing and the Cardiovascular System

Reduction in Arterial Elasticity:

• Arteries and the aorta become stiffer, compromising blood vessel compliance and function.

  • Due to increased collagen and decreased elastin, affecting arterial elasticity and blood flow regulation.

• This leads to elevated aortic pressure, increasing the workload on the heart.

  • Increases afterload on the heart, leading to compensatory changes.

• Can cause left ventricular hypertrophy (enlargement of the heart's left ventricle), resulting in impaired cardiac function.

  • Compensatory mechanism that can lead to heart failure, affecting overall cardiovascular health.

- Increased pulmonary capillary pressure, leading to shortness of breath during exercise, affecting exercise tolerance and quality of life.

Cardiac Tissue Changes:

• Accumulation of lipids and collagen in the heart tissue, altering cardiac structure and function.

  • Fibrosis and reduced contractility, impairing the heart's ability to pump blood effectively.

• Increased cardiac muscle stiffness and reduced compliance, affecting diastolic function.

- Impaired diastolic filling, reducing the heart's ability to relax and fill with blood during diastole.

Heart Valve Flexibility:

• Heart valves, especially the semilunar valves, become less flexible, leading to abnormal functioning, affecting blood flow regulation.

- Calcification and thickening of valve leaflets, resulting in valve stenosis or regurgitation.

SA Node Cells:

• SA node cells decrease, altering electrical activity in the heart, predisposing to arrhythmias.

- Increased risk of arrhythmias, affecting heart rhythm and function.

Heart Rate (HR):

• Maximum HR declines with age, estimated by the formula: 220 - age, reducing exercise capacity.

  • Reduced ability to increase HR during exercise, limiting cardiovascular response to physical activity.

• Response to epinephrine and norepinephrine declines, affecting sympathetic regulation of heart function.

- Blunted sympathetic response, impairing the heart's ability to respond to stress or exercise.

Stroke Volume (SV):

• Can decline due to decreased heart compliance, resulting in less blood being ejected, affecting cardiac output.

  • Reduced preload and contractility, impairing the heart's ability to pump blood effectively.

• SV can also remain the same in some individuals, indicating compensatory mechanisms.

- Due to compensatory mechanisms, such as increased sympathetic drive or ventricular hypertrophy.

Cardiac Output (CO):

• Declines with age, affecting overall cardiovascular performance.

- Reduced HR and SV, impairing the heart's ability to meet the body's circulatory demands.

VO2 max:

• Declines from age 50 due to:-

  • Increased fat tissue, affecting body composition and metabolic function.

  • Decreased cardiac output (CO), limiting oxygen delivery to tissues.

  • Decrease in physical activity, contributing to cardiovascular deconditioning.

### Ageing and the Respiratory System

Vital Capacity Decreases:

• Reduced ability to fill the lungs completely, affecting overall respiratory function.

- Affects the volume of air that can be exhaled after a maximum inhalation, limiting respiratory reserve.

Inspiratory Reserve Volume Decreases:

• Reduced ability to inhale deeply, affecting lung expansion and oxygen intake.

- Limited expansion of the lungs during deep inhalation, reducing the ability to maximize lung capacity.

Expiratory Reserve Volume Decreases:

• Reduced ability to exhale forcefully, affecting the removal of air from the lungs.

- Affects the ability to clear air from the lungs during forced exhalation, potentially leading to air trapping.

Reasons for these changes:

• Weakened respiratory muscles, affecting the strength and endurance of breathing muscles.

  • Reduced strength and endurance of the diaphragm and intercostal muscles, limiting breathing capacity.

• Decreased thoracic cavity compliance (ability to stretch and expand), affecting chest wall movement and lung expansion.

  • Stiffening of the chest wall due to calcification of cartilage, limiting the ability to expand the lungs fully.

- Stiffening of cartilage and ribs, reducing chest wall compliance.

Residual Volume Increases:

- The volume of air remaining in the lungs after maximum exhalation increases, affecting gas exchange efficiency.

Dead Space Increases:

• Due to expansion of bronchioles and alveolar ducts, reducing the area available for gas exchange.

  • Affects the efficiency of gas exchange, limiting oxygen and carbon dioxide diffusion.

• Loss of elasticity in lung tissues, affecting lung recoil during exhalation.

- Reduces the ability of the lungs to recoil during exhalation, potentially leading to air trapping and reduced gas exchange.

Decreased Gas Exchange:

• Reduced surface area due to alveolar wall reduction and thickening, affecting oxygen and carbon dioxide diffusion.

  • Affects the diffusion of oxygen and carbon dioxide, limiting gas exchange efficiency.

  • Gradual Rise in Tidal Volume

  • Mucus buildup

  • Cilia decrease in number and movement

### Ageing and the Urinary System

Kidney Size:

• Kidneys decrease in size, affecting renal function.

- Loss of renal tissue, reducing the overall filtering capacity of the kidneys.

Blood Flow:

• Amount of blood flowing through the kidneys decreases, affecting renal perfusion and function.

  • Reduced renal perfusion, limiting oxygen and nutrient delivery to kidney tissues.

• Afferent and efferent arterioles twist and become irregular, affecting blood flow regulation.

- Affects glomerular filtration, impairing the kidneys' ability to filter waste products.

Glomeruli:

• Glomeruli are destroyed; by age 80, approximately 40% are non-functional, reducing filtering capacity.

- Reduced filtering capacity, leading to decreased ability to remove waste products from the blood.

Nephrons and Collecting Ducts:

• Structure alters, becoming shorter, thicker, and irregular, affecting urine concentration.

- Affects urine concentration, impairing the kidneys' ability to regulate fluid balance.

Secretion and Absorption:

• The ability to secrete and absorb substances declines, reducing the ability to produce concentrated urine, affecting electrolyte and acid-base balance.

  • Affects the regulation of electrolytes and acid-base balance, potentially leading to imbalances.

- This decreases the ability to eliminate toxins effectively, increasing the risk of toxicity.

Increased Risk of Dehydration:

- Due to reduced ability to conserve water, making older adults more susceptible to dehydration.

Hormone Responsiveness:

• Loss of responsiveness to ADH (antidiuretic hormone) and aldosterone, affecting water and sodium balance.

- Affects water and sodium balance, impairing the kidneys' ability to regulate fluid and electrolyte homeostasis.

Renin Secretion:

• Decreases in renin secretion, affecting blood pressure regulation.

  • Affects blood pressure regulation, predisposing to hypertension or hypotension.

### Ageing and the Digestive System

Mucosa and Submucosa:

• Thinning of the mucosa and submucosa layers, affecting absorption of nutrients.

  • Affects absorption of nutrients, resulting in nutrient deficiencies.

• Less mucus is secreted, affecting protection from stomach acid and irritants.

  • Reduces protection from stomach acid and irritants, increasing the risk of gastritis and ulcers.

- Reduced protection from external toxins, increasing the risk of gastrointestinal infections and inflammation.

Liver Function:

• Reduced ability of the liver to detoxify harmful substances, affecting drug metabolism and detoxification.

- Affects drug metabolism and detoxification, increasing the risk of adverse drug reactions.

Infection Susceptibility:

Blood Supply:

• Decrease in blood supply to the digestive organs, affecting oxygen and nutrient delivery.

- Affects oxygen and nutrient delivery, potentially leading to ischemia and tissue damage.

Smooth Muscle Cells:

• Decrease in smooth muscle cells, reducing mobility, affecting peristalsis and bowel movements.

- Affects peristalsis and bowel movements, leading to constipation and other gastrointestinal disorders.

Secretory Organs:

- Less secretion from major secretory organs, affecting digestion and absorption.

Muscles of Mastication

• Muscles of mastication are weakened

• Less mechanical digestion

### Ageing and the Endocrine System

Secretory Activity:

• Gradual decrease in secretory activity in some glands, possibly secondary to reduced physical activity, affecting hormone levels and their physiological effects.

- Affects hormone levels and their physiological effects, impacting various bodily functions.

Growth Hormone (GH):

• GH levels decrease, potentially explaining the decline in muscle and bone mass in older persons, especially those who don't exercise, affecting protein synthesis and bone remodeling.

- Affects protein synthesis and bone remodeling, contributing to sarcopenia and osteoporosis.

Thyroid Hormones:

• Thyroid hormone levels decrease slightly, possibly due to a decline in lean body mass, affecting metabolic rate and energy production.

  • Affects metabolic rate and energy production, potentially leading to hypothyroidism.

- Damage by the immune system may also occur, causing a decline in T3 and T4 production, resulting in hypothyroidism.

Parathyroid Hormone:

• Increase in parathyroid hormone levels but reduced blood levels of Ca^{2+} due to reduced dietary intake, leading to loss of bone matrix to maintain blood levels, affecting calcium homeostasis and bone density.

- Affects calcium homeostasis and bone density, contributing to osteoporosis and increased fracture risk.

Thymus Gland:

• Secretion of thymosin (involved in the development and maturation of the immune system) decreases with age, reducing the efficiency of the immune system and increasing susceptibility to infection.

Ageing and Therm