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Photo Aging
Definition
Exposure to ultraviolet light, UVA or UVB, from sunlight accounts for 90% of the symptoms of premature skin aging. Most of the photoaging effects occur by age 20. The amount of damage to the skin caused by the sun is determined by the total lifetime amount of radiation exposure and the person\'s pigment protection.
Changes in the epidermis caused by the sun include thinning of the epidermis and the growth of skin lesions such as actinic keratoses, basal cell carcinomas, and squamous cell carcinomas.
In the dermis, sun effects cause collagen to break down at a higher rate than with just chronologic aging. Sunlight damages collagen fibers and causes the accumulation of abnormal elastin. When this sun-induced elastin accumulates, enzymes called metalloproteinases are produced in large quantities. Normally, metalloproteinases remodel sun-injured skin by manufacturing and reforming collagen. However, this process does not always work well and some of the metalloproteinases actually break down collagen. This results in the formation of disorganized collagen fibers known as solar scars. When the skin repeats this imperfect rebuilding process over and over wrinkles develop.
Photodamage may be chronic or acute; acute photodamage is a sunburn. Photoaging and photodamage (dermatoheliosis) are terms used interchangeably to describe those chronic changes in the appearance and function of the skin caused by repeated sun exposure rather than by the passage of time (the latter called intrinsic or chronologic aging). Overwhelming epidemiologic and laboratory evidence indicates that sun exposure and other sources of UV radiation (UVR) play the major role in causing the undesirable skin changes of fine and coarse wrinkles, roughness, laxity, mottled pigmentation, actinic lentigines, actinic keratoses, leathery texture/coarseness, scaling/xerosis, sallowness, and telangiectasia. Cigarette smoking is the only other environmental factor that has been related to the development of changes in the skin associated with aging.
Because there is equally compelling evidence that UVR, from sun exposure or artificial sources, or both, is associated with an increased incidence of benign, premalignant, and malignant skin neoplasms, the changes of photoaging/photodamage have important epidemiologic significance, as well as aesthetic implications and are therefore not trivial concerns. No credible scientific evidence contradicts the relation of sun exposure to the development of skin cancer and the undesirable results of photoaging and photodamage.
Scope
The sun, although necessary for life, is also a natural hazard. On average, 80% of lifetime sun exposure occurs during multiple brief exposures not intended to produce tanning. Most white Americans manifest some changes of photoaging/photodamage before 50 years of age. Persons with fair skin who live in areas of high solar energy exposure and who have high levels of sun exposure because of occupation or recreation are at greater risk for photodamage. The undesirable changes of photoaging and photodamage, as well as the development of skin cancers including melanoma, will likely become even more common if the ozone layer continues to be depleted. The U.S. Environmental Protection Agency estimates that 12,000,000 additional cases of skin cancer and 210,000 additional skin cancer deaths will occur in the next 50 years just from the currently existing amount of ozone depletion. UVR from sources such as those delivered in tanning parlors contributes to the problem. The economic implications of photoaging/photodamage are evident in that a significant portion of the estimated $14 billion per year spent in the United States on cosmetics is specifically intended to conceal the changes of photoaging/photodamage. A significant amount of money is spent on aesthetic surgical procedures attempting to reverse the changes of photoaging/photodamage. Early recognition and treatment of photoaged/photodamaged skin may decrease the incidence and therefore the cost of treating premalignant and malignant skin lesions.
Issue
Photoaging and photodamage are real medical problems, not just cosmetic or aesthetic concerns, because prevention of photoaging and photodamage may prevent the progression of changes toward skin cancer.
Education and prevention are among the most cost-effective ways to manage the problem. The use of protective clothing, sunscreens, and sun avoidance should be encouraged for everyone.
Photoaging and photodamage may be at least partially reversible with photoprotection and treatment.
The use of sunscreens that protect against UVB and UVA should be encouraged.
There is no safe way to tan.
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