Ageing (or aging)

Ageing (or aging) is the process of becoming older. It represents accumulation of changes over time. Ageing is one of the greatest risk factors for most human diseases. The causes of ageing are unknown and the process is not properly understood.

Many changes occur in the body as it grows. After maturity, age-related changes bring about gradual decline in body functions. The peak of mature physiological function is short lived. Organs such as kidneys start declining after the age of 30. In both infancy and old age body functions are less efficient. For examples, in both infants and old people, temperature regulation is less effective.

Most organs of the body mature during puberty. They are most efficient during early adulthood. The body can repair the tissues of most organs. However, the brain and myocardium are exceptions.

At maturity most organs have considerable spare capacity or functional reserve. Functional reserve is the remaining capacity of an organ to perform its physiological activity. It indicates the loss of function which must occur before physiological changes become evident. Functional reserve declines with age.

The causes of ageing are not known and the process is poorly understood. Several theories have been proposed to explain ageing. A number of factors affect the lifespan of an individual. Some of these factors are genetic. However, environmental factors, nutrition and lifestyle (smoking, drinking alcohol and lack of exercise) strongly influence lifespan.

Effects of ageing on the body

System	Physiological changes	Common consequences
Nervous system	Motor control of movements diminishes Slower conduction of nerve impulses	Body movements take longer and are prone to fail Poor control of vasodilation, vasoconstriction & baroreceptor reflex
Special senses	Hair cells of the ear get damaged Eye lens become stiff and/or opaque (leading to cataract) Taste and smell diminish	Hearing impairment Loss of vision Food tastes plain; Cannot smell
Respiratory system	Drying of mucous membranes Stiffening of rib cage Decline in respiratory function	Increases risk of infections Reduced respiratory volume Improper regulation of arterial blood gas levels
Cardiovascular system	Hardening of blood vessels Reduced cardiac functioning and efficiency	High blood pressure; Increased risk of rupture of blood vessels Reduced cardiac output and cardiac reserve
Endocrine system	Decline in functioning of β-cells of pancreas Estrogen deficiency in women	Type 2 diabetes
Digestive system	Loss of teeth Reduced peristalsis Decline in liver mass and function	Improper digestion Constipation Reduced liver function may increase risk of drug toxicity
Urinary system	Reduction in number of nephrons	Impaired fluid balance regulation Increased risk of dehydration
Resistance and immunity	Reduction in resistance and immunity	Increased risk of infection Injuries may take a long time to heal
Musculoskeletal system	Loss of bone Hardening of cartilage	Increased risk of fractures Stiff joints Osteoporosis
Reproductive system	Female menopause	Cessation of reproductive ability in females Reduced fertility and erectile dysfunction in males