Photoaging

In elderly Americans, most changes in the skin's appearance are the result of chronic exposure to ultraviolet (UV) radiation from sunlight. This process, known as photoaging, differs clinically, histologically, and physiologically from aging itself, although most patients and many physicians do not make the distinction. Elderly people whose pigmentation or lifestyle protects them from photodamage often look younger than their chronologic peers, while conversely, people who do not protect their skin may look considerably older. Risk factors for photoaging besides age and UV exposure include a fair complexion, difficulty tanning, and easy sunburning.

Some skin diseases that are common in the elderly, such as skin cancer, occur almost exclusively in photoaged skin.

Symptoms and Signs

Photoaged skin is characterized by fine and coarse wrinkling, irregular mottled pigmentation, lentigines (brown macules--see Photo 122-3), roughness, sallowness, and telangiectasis. Poorly defined rough, red dysplastic areas of actinic keratoses are associated with more severe damage and a higher risk of skin cancer. The overall appearance may be hypertrophic or atrophic, depending on the patient's complexion and the severity of the photodamage. Actinic purpura (also called Bateman's, solar, or senile purpura) appears as nonpalpable ecchymotic areas usually on the extensor forearms of the elderly (see Photo 122-4) and is thought to represent excess RBCs in photodamaged connective tissue. RBCs are present in high amounts because they extravasate from fragile vessels and are cleared slowly. Thrombocytopenia is often suspected, but platelet function and quantity are not altered. Depigmented stellate pseudoscars on the extremities also indicate photoaging. Cigarette smoking exacerbates the coarse wrinkling and skin cancer risk of photoaging.

Histologic changes in photoaged skin include epidermal dysplasia and atypia, decreased numbers of Langerhans' cells, and striking dermal elastosis (deposits of abnormal elastic fibers). Loss of immunologic and inflammatory responsiveness is greater in photoaged skin than in skin with only age-related changes.

Treatment

Topical retinoids are the only proven effective drug treatment for photoaging. All-trans-retinoic acid is the best studied and improves global appearance, fine and coarse wrinkling, roughness, mottled hyperpigmentation, and lentigines within 4 to 6 mo. New capillary formation, collagen synthesis, anchoring fibril formation, regularization of epidermal melanin distribution, and disappearance of premalignant actinic keratoses may also occur. Topical alpha hydroxy acids are claimed to offer similar benefits but are less well studied.

Initial treatment consists of applying tretinoin cream 0.05% or tazarotene cream 0.1% once/day at bedtime. The patient should be warned that mild erythema and peeling (retinoid dermatitis) may occur, although elderly skin is usually less prone to these problems. If necessary, the regimen can be changed to every other day until tolerance improves. After 8 to 12 mo, a maintenance regimen of 1 to 3 applications a week may be instituted. Regular sun protection is essential to minimize on-going damage.

Topical 5% fluorouracil cream bid for 3 to 4 wk effectively treats many actinic keratoses. Similar regimens with imiquimod 5% cream or diclofenac gel 3% or a single session of photodynamic therapy using the porphyrin precursor amino-levulinic acid and activating wavelengths of light are also highly effective at clearing actinic keratoses, with disappearance of all lesions in 50 to 75% of patients after several months. However, for patients with relatively mild photodamage and few keratoses, cryotherapy (freezing with liquid nitrogen) of individual lesions is often preferable to treating the entire face or bald scalp with one of these regimens, due to the substantial treatment-associated inflammation.

Little or no data support the claims made for herbal remedies (eg, green tea extract), antioxidants (eg, vitamins C and E), collagen and other proteins, embryo extracts, N6-furfuryladenine, or other nonprescription additives. All of these agents are available in topical preparations. Herbal remedies and antioxidants are available as oral preparations also.

A dermatologist or plastic surgeon may reduce the prominence of skin folds by injecting skin fillers (eg, collagen or hyaluronic acid) and may reduce the prominence of expression lines by injecting botulinum toxin. Surgery (eg, face-lift or blepharoplasty) may remove redundant skin and "re-drape" sagging skin, and various forms of laser surgery, dermabrasion, and chemical peels can even skin color and surface texture. The healing time after "resurfacing" procedures such as dermabrasion and chemical peels depends on the depth of skin removal. Time during which effects of treatment are visible varies. After microdermabrasion (a "lunchtime peel"), a person can go back to work the same day and have only mild erythema. In contrast, erosion and crusting may last for a week or more if the entire epidermis is destroyed. In all cases, healing time tends to be longer in the elderly than in younger adults.

Laser removal of small vascular lesions (eg, telangiectasias, angiomas) and discrete pigmented lesions (eg, lentigines) is usually helpful and very well tolerated. Medical evaluation is not indicated before undertaking these minor office procedures that do not affect the skin's barrier layer.

Medical and surgical treatments for photoaging are not covered by 3rd-party payers, including Medicare.

Prevention

Because damage due to photoaging is cumulative, preventive measures are most successful if begun during childhood. However, preventive measures are important at any age. Avoidance of sun exposure and regular use of sunscreen prevent progression of photoaging; preventive measures alone minimally reverse existing changes, although regression of actinic keratoses is well documented after prolonged periods of sun avoidance.

Initial summer exposure to bright, midday sun should be very brief and supplemented with protection (by sunscreen application, clothing, or both). In temperate zones, exposure is less hazardous before 10:00 AM and after 3:00 PM because more sunburn-producing wavelengths are filtered out by the atmosphere. Fog and clouds do not eliminate risk, and risk is increased at high altitude.

Fabrics with a tight weave block the sun better than do those with a loose weave. Special clothing that provides high sun protection is commercially available. Broad-brimmed hats protect the face, ears and neck.

Sunscreens can also protect from sunburn and chronic photodamage. In the US, the FDA rates sunscreens by sun protection factor (SPF): the higher the number, the greater the protection. Products with SPF > 30 are recommended. The SPF, however, only quantifies the protection against UVB exposure; there is no scale for UVA protection, although products that protect against both (broad spectrum products) are at least moderately effective. Sunscreens are available in various formulations, including creams, gels, foams, sprays, and sticks. Self-tanning products do not protect from UV exposure.

Most sunscreens contain several chemicals that absorb, reflect, or scatter light. Common chemical sunscreen agents mostly absorb UVB rays and include the aminobenzoates, which includes p-aminobenzoic acid (PABA), salicylates, cinnamates, benzophenones (eg, avobenzone), and the anthrilates. Of these, the benzophenones are particularly effective at screening UVA rays. Zinc oxide and titanium dioxide block both UVB and UVA rays. Micronized formulations of these products have significantly improved their cosmetic acceptability. Because sunscreens also block UV-induced vitamin D formation in the skin, the elderly should be advised to consume vitamin D-fortified milk or orange juice or vitamin D supplements (800 IU per day) to safeguard against osteomalacia. Sunscreen failure is common and usually results from insufficient application of the product, application too late (sunscreens should optimally be applied 30 min before exposure), or failure to reapply after swimming or exercise.

Cigarette smoking should be discouraged not only for reasons of general health but also because smoking exacerbates photoaging in a dose-related fashion and increases skin cancer risk.

This topic was last updated March 2006.