Table 1.

The ageing process: physiological changes, pathophysiological consequences and associated diseases

System	Ageing-related change	Consequence	Age-dependent and older age- related disease/outcomes
Endocrine	Fat deposition in pancreas; ↓ in insulin signalling Thyroid atrophies, ↑ fibrosis, ↑ nodule formation ↑ Parathyroid fat deposition but no atrophy Atrophy of ovaries; ↓ testosterone levels, with asynchronous feedback to Luteinizing hormone	↓ Response to glucose-lowering medications aimed at pancreatic function Changes in body composition Menopause Late-onset male hypogonadism	Type 2 diabetes Thyroid disorders Orthostatic hypotension Osteoporosis
Cardiovascular	↑ Left ventricular wall thickness with ↓ cavity size ↑ Fat deposits; ↑ vascular stiffness with ↓ responsiveness to drugs	↑ Systolic BP, ↑ pulse wave velocity, ↓ peak ventricular filling rate, ↓ maximal heart rate and variability, ↓ V̇O2max	CVD Heart failure Hypertension ↓ Endurance
Neurological	↓ Neurons, ↓ axon potential, ↓ dendrite branches	Memory loss	Cognitive impairment and dementia Self-care deficit Risk of delirium
Muscular	↓ Peak strength of contraction, slower contraction and relaxation, ↓ muscle tone and contractility	↓ Muscle strength, ↓ endurance	Sarcopenia Impaired mobility/gait Functional decline and disability
Optical	↑ Lipid infiltrates/deposits, ↑ thickening of the lens, ↓ pupil diameter	Vision impairment, presbyopia, cataracts	Macular degeneration, increased risk of falls and loss of independence
Auditory	↑ Tympanic membrane thickens, loss of both elasticity and efficiency of ossicular articulation	Conductive hearing loss	Presbycusis
Skeletal	↓ Bone density, stiffer joints, thinner intervertebral discs, flattening of foot arches	↓ Height, scoliosis, kyphosis, slower and unsteady gait	Osteoporosis and osteoarthritis Greater risk for falls and fractures
Gastrointestinal	Abnormal peristalsis, ↓ gastric acid, mucosal cell atrophy	Dysphagia, malabsorption (iron, vitamin B12, calcium), increased risk for malnutrition	Unintentional weight loss Constipation
Renal	↓ Kidney size and weight, ↓ functional glomeruli, ↓ length/function of renal tubules	↓ Reabsorption capacity, impaired renal function	Chronic kidney disease
Immune	↓ Memory cells, ↑ autoimmune antibodies ↓ T lymphocytes, ↓ natural killer cells, ↓ cytokines	↓ Immune function (requires more stimulus and more time to become activated), ↓ response	Greater risk for infections and less effective response to control them Some types of cancer
Dermal	↓ Skin thickness, ↑ collagen cross-links	↓ Elasticity, ↑ fungal infections, neoplasms	Pressure ulcers

Table adapted from [14,19,20]