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As life expectancy has increased and “baby boomers” have begun to enter middle age, interest has increased in slowing the aging process. Implied in this escalating interest is the confidence that greater scientific knowledge and advancements in technology may allow us to control the physical manifestations of aging. In the meantime, more and more people are becoming aware of the external factors implicated in premature aging. Although dermatologists have discussed, since the end of the 19th century,1 the notion that sunlight contributes to premature aging, there remains a great need for education to convince people of the hazards posed by sun exposure.
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The consequences to the skin of chronic sun exposure are readily apparent when one compares the exposed skin of the face, hands, or neck to the unexposed skin of the buttocks, inner thigh, or inner arm (Fig. 6-1). This sun damage can be highlighted by using a Wood’s lamp, blue light, or an ultraviolet camera system, rendering the epidermal pigment component more noticeable (Figs. 6-2, 6-3, and 6-4). Showing such results to sun-seeking patients can prove useful in convincing them of the havoc that the sun has wreaked on their skin.
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The sun is not the sole source or cause of skin aging. It is the major external cause among several components, both endogenous and exogenous. This chapter will concentrate, though, on the role of the sun on the extrinsic aging process of the skin, also known as photoaging.
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There are two main processes of skin aging, intrinsic and extrinsic. Intrinsic aging reflects the genetic background of an individual and results from the passage of time. It is inevitable and, thus, beyond voluntary control. Extrinsic aging is engendered by external factors such as smoking, excessive use of alcohol, poor nutrition, and sun exposure, which in many cases can be reduced with effort. This process, then, is not inevitable and, by definition, refers to premature skin aging. It is believed that as much as 80% of facial aging can be ascribed to sun exposure.2
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INTRINSIC VERSUS EXTRINSIC AGING
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Intrinsically aged skin is smooth and unblemished, with exaggerated expression lines but preservation of the normal ...