It is extremely difficult to draw a sharp line between the deleterious effects of normal aging and the deleterious effects of the diseases of aging. The diseases most commonly manifested in the elderly are disorders of the heart, blood vessels, and joints. The heart disease of the elderly is related to the generalized vascular disease known as arteriosclerosis, which frequently attacks the major coronary arteries of the heart. Arteriosclerosis and arthritis will therefore be briefly touched upon here. More extended discussions may be found in cardiovascular disease and in joint disease. These problems and other aspects of aging are also considered in human aging.
Arteriosclerosis is not a specific disease. The term is applied to all diseases that cause hardening of the arteries. Several minor processes can induce hardening of the arteries, but the overwhelming preponderance of cases of arteriosclerosis are caused by atherosclerosis. This disorder, which eventually affects all individuals to varying degrees, begins relatively early in life in most persons. There are great variations, however, in the severity of this disease among individuals and among racial, national, and ethnic populations. These differences depend on the presence or absence of risk factors such as diet, hypertension, tobacco smoking, diabetes, obesity, family history, and stress.
Atherosclerosis is characterized by the deposition of fats (cholesterol and other complex lipids) in the linings (intima) of the arteries. It is accompanied by cell injury, cell death, and scarring and sometimes produces total obstruction of an artery. Atherosclerosis has a predilection for the aorta, the major artery of the body, and the arteries of the heart, brain, and legs. Atherosclerosis of the arteries of the heart (the coronaries) causes myocardial infarction, otherwise known as heart attack.
When atherosclerosis narrows but does not totally block the coronary arteries, the heart also is injured by lack of adequate blood supply and nutrition and becomes progressively smaller and weaker; even though this disease is not as life-threatening as a heart attack, it nonetheless frequently causes heart failure, an inability of the heart to deliver an adequate supply of blood to the tissues. Atherosclerosis of the arteries of the brain is the usual cause of stroke. When the arteries to the legs become affected in this way, gangrene may develop.
Arthritis, probably the second most common and distressing disease among the elderly, is a disease of the joints. It causes considerable pain, discomfort, and lack of mobility and so makes life burdensome. Moreover, arthritic individuals are more subject to other illnesses. Degenerative arthritis (osteoarthritis) is common to all elderly people to a lesser or greater degree. Osteoarthritis usually begins in the fourth decade of life and slowly progresses with increasing age. Coinciding with the characteristic degeneration of the joints are changes involving the bone itself. The bone of elderly persons is known to be less dense and more brittle; it tends, therefore, to fracture more easily. It also heals with greater difficulty.
There are many subtle changes that occur with the normal aging process. These may include degenerative changes in the brain, leading to impaired mental ability and even senility. As this damage is usually accompanied by atherosclerosis of the arteries of the brain, it is difficult to know how much of the change is the result of impaired blood flow and how much is related to normal aging. Finally, but of no less significance, is the general decline in the body's ability to defend itself against disease. Thus elderly persons are more susceptible to infections, trauma, and a number of other bodily defects. Simple, uncomplicated pneumonia, which might be easily tolerated by the young, healthy adult, may be fatal for an elderly, weakened person.