The aging body

Aging can be seen biologically as a combination of the gradual dysfunction of cells, the reduced efficiency and eventual breakdown of organs, and the eventual degeneration of the whole body. Some research indicates that humans and other animals may have a built-in “biological clock’ which regulates the process, but this proposal is still very tentative. On a cellular level, it is thought that ‘mistakes’ accumulate as cells age and go through their own life cycles. As the generations of cells pass, they are no longer as healthy or effective in their jobs as their ancestors. It is thought that, for each generation, minor mutations in the genetic material occur, and these accumulate over the years. For example, skin cells gradually become deficient at producing the protein collagen, which supports healthy skin and helps to keep it supple and elastic. Under laboratory conditions of tissue culture, generation 10 of skin cells produces less collagen than generation 1. Hence the wrinkled skin of old age. In fact some researchers have noted that under artificial culture conditions, most types of body cell seem to degenerate and die rapidly after about 50 generations. The interdependent nature of body systems poses an additional problem with increasing age. During earlier years, illness or impaired function of one organ or system can be compensated for by another. However, as all systems age and gradually become less efficient, stresses and strains are not absorbed so easily. This is an inherent weakness of any complex, multi-system design.

Geriatrics – the medical science of old age – differs from the medicine of other age groups in several ways.

Most importantly, older people tend to have more than one disease or disorder at a time. The conditions may have an additive effect, or one may be difficult to treat because its therapy affects another. Diagnosis and treatment of disease in old age, therefore, often requires a balancing act and a question of priorities on the part of the medical team. But it should be emphasized that ill-health is by no means inevitable in old age. An individual’s future health prospects are a complex combination of genetic influences, previous illness, health and activity in former years, and a mental determination to stay fit and active for as long as possible. Researchers have estimated that if all deaths were the result of natural causes, our average life expectancy would increase by only about ten years. Our biological possibilities thus lie near the age most deaths are caused by disease or a disorder. The total eradication of coronary heart disease would add about six years to the average life span of a population. Eradication of cancer would add only two.

Diet needs especial care among the elderly if they are to avoid malnutrition. All elderly people still need protein in such foods as meat, fish and cheese, as well as the usual supplies of fresh fruit and vegetables. The problem of not being able to chew food can be overcome by pureeing or mincing.

The nervous system and ageing

The nervous system begins to age from about our teens onwards with the loss of brain cells at the rate of 10,000 each day. Tests performed to check our reflexes reveal that as we get older the pupil of the eye becomes slower to respond to changes of light, and reflex jerks of the knee and ankle are harder to obtain. Curiously, some reflexes we have as babies may return, such as sucking responses to stimulation around the mouth.

One reason for these changes in old age is the thinning and weakening of the insulating and conduction-speeding myelin sheath of nerve fibres. The result is that many nerve pathways are no longer complete; other conditions such as diabetes can make this worse. Senses such as taste and smell decline, as does our sensation of cold. Old people are more liable to suffer from hypothermia partly because they are not fully aware of how cold they are.

Cardiovascular and respiratory systems

With advancing years the heart and lungs lose much of their reserve capacity. The effects of this are noted most when one tries to perform strenuous exercise. Some arteries gradually become narrow because of fatty deposits and lose their flexibility, resulting in increased blood pressure, which increases the heart’s work load.

High blood pressure in old age may be relatively symptomless, but it can damage other organs such as the urinary system or even the brain. Although it seems contradictory, old people often also suffer with postural hypotension. When they get up early in the morning, they sometimes feel dizzy. The heart is losing pumping efficiency and it reacts quickly to rapid changes in position. For a short while the supply to the brain is decreased, causing fainting or dizziness. To combat this the person is advised to get up much more slowly, which gives the heart time to adapt to the changes in the amount of blood that has to be pumped to the brain.

Blood vessels may weaken at certain points, especially in the brain, which can give rise to an aneurysm. If this bursts a cerebral haemorrhage will develop, which is a common cause of death in the elderly. Respiration in old age is influenced by what happens to the heart, and the reverse is also true. Lung conditions often lead to damage of the right side of the heart, which pumps blood to the lungs. Chronic bronchitis affects many elderly people, as does an even more severe condition, emphysema. As the lung ages, its connective tissue loses elasticity. The bronchial cartilages harden, and mucous glands proliferate. These effects are exacerbated by atmospheric pollution and tobacco smoke. Stiff lungs clogged with mucus provide ‘ideal’ conditions for bacterial infection, and coughing does further damage. With the lungs less efficient, the right side of the heart has to work harder.

Cancer of the respiratory system is also seen in old age, although this is correlated strongly with cigarette smoking rather than simply aging.

Digestion and nutrition

Old people need less food to sustain them, but because they commonly experience the loss of teeth this sometimes results in them altering their diet for the worse because they find it hard to eat uncooked or unprocessed foods, meat and raw fruit. Constipation often arises in old age because of the weakening of the nerve centre in the spinal cord, which controls the evacuation of the bowels. Because less food is being eaten, there is a reduction in the volume of faeces which provides even less stimulation for the bowel to empty itself.

Diverticulosis often affects the large intestine of the elderly: the intestinal wall weakens and develops small sac-like swellings that can become inflamed.

With age there is a decline in the eye lens’ capacity for accommodation (I.e. its ability to become more convex). This gives rise to problems with, for example, reading or sewing (age-related farsightedness). Spectacles with corrective lenses can alleviate this problem.

In terms of personality, new patterns of thought become harder to organize as we age. Imagination is more difficult. Old people who are subject to a great deal of sudden emotional change may suffer a nervous breakdown.