The Human Aging Process and aging research

With age, many of the body’s functions decline. The decline that occurs in normal aging, however, is not usually considered the same as disease, although the distinction is not always clear. As people age, blood sugar levels increase more after eating carbohydrates than they do in younger people; however, the very large increases that occur in diabetes are not considered normal aging. Mental decline that includes more difficulty learning new languages and increased forgetfulness is nearly universal with advanced age and is considered normal aging; however, the serious mental decline of dementia, with its extreme loss of short-term memory, ability to learn, and understanding of the environment, although common in late life, is considered a disease. Alzheimer’s disease is an abnormal process,

Longevity

The average life expectancy of Americans has been increasing dramatically over the past century. A male child born in 1900 could expect to live only 46 years; a female child, 48 years. Today, however, a male child can expect to live more than 73years; a female child, nearly 80 years. Although many of these gains in longevity can be attributed lo the significant decrease in childhood mortality, life expectancy at every age beyond 40 has also increased dramatically. For example, a 70-year-old man can now expect to live until age 83, and a 70-year-old woman to age 85. Despite the increase in average life expectancy, the maximum life span the oldest age to which people can live has changed little. Despite the best genetic makeup and medical care, no one seems to live much beyond 125 years, although some experts suggest that this number may be slowly increasing. Currently, a person has a 1 in 2 billion chance of living to the age of 120.

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Several factors influence longevity. One is heredity, which primarily influences whether an individual will contract a disease. For example, inheriting an increased risk of developing high cholesterol levels is likely to result in a shorter life, whereas inheriting genes that protect against heart disease and cancer can help to ensure a longer life. Another important influence on longevity is lifestyle; avoiding smoking, avoiding drug and alcohol abuse, maintaining a healthy weight and diet, and exercising appropriately help people avoid disease. Exposure to environmental toxins can shorten life expectancy even among people with the most robust genetic makeup. Medical care contributes to increased survival by preventing or treating diseases after they are contracted, especially when infectious diseases, cancer are cured.

Bodily Changes

The human body changes in many noticeable ways with age. Often, the first signs of aging involve the musculoskeletal system. By age 35, peak performance, even among superior athletes, begins to decline. Sensory organs also begin to change early in mid-life. A common development, for example, is presbyopia, in which the eye can no longer focus without using reading glasses or changing to bifocals. Another, if later, common development is presbycusis, or age-associated hearing loss, which initially affects the ability to hear the highest pitches and, gradually, the lower pitches as well. Therefore, older people may find that violin music no longer sounds as exciting as if did when they were younger. In most people, the proportion of body fat increase by more than 30% by late age.

The distribution of fat also changes: There is less fat under the skin and more in the abdominal area. Thus, skin becomes thinner, wrinkled (although sun exposure and smoking have a greater influence on wrinkling), and more fragile, and the shape of the torso changes. Not surprisingly, most internal functions also decline with age. These functions generally peak shortly before age 30 and then begin a gradual but continuous decline. Even with this decline, however, most functions remain adequate throughout life, because most organs have considerably more functional capacity than the body needs (functional reserve). For example, even if half the liver is destroyed, more than enough liver tissue remains to maintain normal function.

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