The major extrinsic agent causing damage is sunlight. This damaging effect is termed photoaging. It is the result of prolonged and repeated damage caused by ultraviolet radiation, most frequently sunlight. The main damaging effect is caused by the shorter wavelength radiation (UVB), which has a limited penetration of the upper epidermal cells. The longer wavelength radiation (UVA) penetrates into the dermis and further increases the damage.
The main clinical change caused by sunlight is wrinkling. The elastic fibers present in the upper dermis swell initially. Later they become coarse and twisted, and finally lose their fibrous character. Under the microscope, the fibers are a diffuse, characterless mass that stains differently than the normal skin. The coarser, deeper, and more voluminous collagen fibers show similar degradation. This all leads to a loss of skin elasticity termed ‘‘elastotic degeneration.’’ If this skin is pinched and pulled, it fails to rebound to its normal state over a short period of time. In contrast, youthful skin or skin that is usually covered in the older person rapidly springs back to its normal state.
Sunlight is essential to well-being, and in moderation it enhances immunity; it makes Vitamin D in the skin; it induces a normal pigmentary protective response; and it makes people feel and look ‘‘good.’’ Episodic excessive exposure, or a cumulation over many years, can be damaging and is particularly related to the pigment character of the individual’s skin.
How much any individual shows the changes in the skin due to a lifetime of chronic sun exposure and weathering depends on the amount of sun to which the person has been exposed and where, geographically, this occurred. Other modifying factors include genetic endowment, skin pigmentation (dark, fair or gingery), and lifestyle factors such as smoking.
A wrinkled, coarse skin is the most characteristic of these changes. Smokers particularly have enhanced facial aging. Their skin wrinkling and appearance are more aged than those of nonsmokers. The deeper folds of the expression lines may be more emphasized.
The wrinkling may give cosmetic concern; many active old people wish to retain a youthful appearance. ‘‘Cellulite’’ is a harmless form of deep dimpling which occurs on the outer thighs. Some of the concerns can be met by the many cosmetic applications on the market. In other situations, cosmetic surgery can bring much benefit.
Medicine EncyclopediaAging Healthy - Part 4Skin - Intrinsic Changes, Extrinsic Changes, Growth And Changes In Color, Skin Cancer, Conditions Of The Normal Aging Skin