Aging

Aging refers to the time-sequential deterioration that occurs in most animals including weakness, increased susceptibility to disease and adverse environmental conditions, loss of mobility and agility, and age-related physiological changes. Aging is usually understood to include reductions in reproductive capacity. It is assumed that aging includes changes in reproductive capacity including behavioral patterns such as “reproductive vigor” or strength of the urge to mate. Reproductive capacity and aging have similar theory issues as will be discussed later. Aging is a syndrome of changes that are deleterious, progressive, universal and thus far irreversible.

Aging changes occur to molecules (DNA, proteins, lipids), to cells and to organs. Diseases of old age (diseases which increase in frequency with age, such as arthritis, osteoporosis, heart disease, cancer, Alzheimer’s Disease, etc.) are often distinguished from aging per se. But even if the aging process is distinct from the diseases of aging, it is nonetheless true that the aging process causes changes that increase the probability that diseases of old age will occur.Some gerontologists prefer to use the word senescence because “aging” implies that the passage of time necessarily results in deterioration (biological entropy) — which is certainly not true during the early, developmental, time of life (before the age of 10 or 12 in humans). I will retain the word “aging” because I believe the association between aging & deterioration is universal as adult years progress and because the distinction between aging & development is very strongly established in conventional language. Also, shorter words make for slightly faster reading.

Human beings reach a peak of growth and development around the time of their mid 20s. Aging is the normal transition time after that flurry of activity. Although there are quite a few age-related changes that tax the body, disability is not necessarily a part of aging. Health and lifestyle factors together with the genetic makeup of the individual, and determines the response to these changes. Body functions that are most often affected by age include:

• Hearing, which declines especially in relation to the highest pitched tones.
• The proportion of fat to muscle, which may increase by as much as 30%. Typically, the total padding of body fat directly under the skin thins out and accumulates around the stomach. The ability to excrete fats is impaired, and therefore the storage of fats increases, including cholesterol and fat-soluble nutrients.
• The amount of water in the body decreases, which therefore decreases the absorption of water-soluble nutrients. Also, there is less saliva and other lubricating fluids.
• The liver and the kidneys cannot function as efficiently, thus affecting the elimination of wastes.
• A decrease in the ease of digestion, with a decrease in stomach acid production.
• A loss of muscle strength and coordination, with an accompanying loss of mobility, agility, and flexibility.
• A decline in sexual hormones and sexual functioning.
• A decrease in the sensations of taste and smell.
• Changes in the cardiovascular and respiratory systems, leading to decreased oxygen and nutrients throughout the body.
• Decreased functioning of the nervous system so that nerve impulses are not transmitted as efficiently, reflexes are not as sharp, and memory and learning are diminished.
• A decrease in bone strength and density.
• Hormone levels, which gradually decline. The thyroid and sexual hormones are particularly affected.
• Declining visual abilities. Age-related changes may lead to diseases such as macular degeneration.
• A compromised ability to produce vitamin D from sunlight.
• A reduction in protein formation leading to shrinkage in muscle mass and decreased bone formation, possibly leading to osteoporosis.