NEW YORK ― In skin of color, ultraviolet (UV) and visible light protection are crucial to maintaining a healthy and youthful appearance. Although the mechanism by which UVA, visible light, and infrared damages the skin is still under study, reactive oxygen species (ROS) are thought to play a major role, said Steven Q. Wang, M.D., at the Skin of Color Seminar Series held here in April.
Individuals from all races can develop skin cancers in sun-exposed sites, yet many patients with skin of color do not know that they need comprehensive photoprotection to prevent skin cancer and photoaging, said Dr. Wang, who is director of dermatologic surgery and dermatology, Memorial Sloan-Kettering Cancer Center at Basking Ridge, N.J.
In the U.S., skin of color accounts for 28% of the population. “Skin of color represents a heterogeneous group of individuals, comprised of highly phenotypically and genotypcially diverse groups,” he said. Current classification is largely socially based rather than biologically defined. For example, the range of pigmentation levels is wide even within various Asian countries, depending on geography. In the U.S., a melting pot or interracial marriage creates further diversity of pigmentation level.
Despite all that is known about the value of sunscreen in protecting from sunburn, premature skin aging and skin cancer, sunscreen use is low in people with skin of color. Some 62 to 74% of African Americans and 47 to 69% of Hispanics report never or rarely using sunscreens. Use or protective clothing is similarly low in these groups.
Sunscreen use tends to be occasion based, said Dr. Wang, with most persons applying sunscreen only when they think they need it. In addition, multiple studies have shown that consumers under-apply sunscreen by as much as one half or one third of the recommended amount. High SPF sunscreen provides superior photoprotection compared with their lower SPF counterparts. In a split-face randomized double-blind study of 200 subjects with an average of six hours of sun exposure, 55% of subjects were more sunburned on the side of the face that received SPF 50+ compared with the side that received SPF 100+.
Photoprotection compliance in African Americans and Hispanics may be suboptimal because these groups may be less concerned about sunburn and skin cancer, said Dr. Wang. In contrast, Asians are more compliant than the Caucasian population “because they understand the risk of pigmentations as well as wrinkle formation, so that’s their reason for using photoprotection.”
Recommendations for photoprotection from the American Academy of Dermatology in people of color are similar to those in the Caucasian population. A broad-spectrum sunscreen with an SPF of 30 or greater is recommended. Sunscreens that contain titanium dioxide and zinc oxide are generally better accepted by people of color because of better cosmesis on dark skin.
UVA PLUS VISIBLE LIGHT IS CULPRIT IN PIGMENTATION
Aside from the poor compliance, sunscreen offers no protection for visible and infrared light. Pigmentation in skin types IV-VI induced by visible light is darker and more sustained than that for long-wavelength UVA (UVA1), said Dr. Wang, citing data from Mahmoud et al (J Invest Dermatol 2010;130:2092-7). Following irradiation, UVA1-induced pigmentation faded rapidly over the course of 2 weeks, whereas it was sustained over the same 2-week period when induced by visible light.
Sunscreens with titanium dioxide, zinc oxide, and iron oxide have more protection against visible light than do conventional sunscreens, he said.
HOW UVA WORKS
The complete mechanism by which UVA, visible, and infrared light damages the skin is still being studied. “One of the mechanisms responsible for visible light and long-wave UVA light to generate pigmentation, we believe, is through production of free radicals,” Dr. Wang said. He and colleagues have shown ROS to promote the release of inflammatory cytokines, to decrease procollagen synthesis, and to increase elastin expression, leading to decreased collagen formation and increased collagen breakdown, resulting in clinical signs of photoaging, solar elastosis, deep wrinkles, coarse textures, telangiectasias, and pigmentation. UV is not the only agent that induces free radicals; ROS generation can be intrinsic from biological activities.
The body has a natural ROS defense system consisting of endogenous enzymatic (ie, vitamin C, vitamin E, glutathione, lipoic acid, polyphenol, CoQ10, and vitamin A) and nonenzymatic (ie, superoxide dismutase, catalase, glutathione reductase, thioredoxin reductase, methionione, and sulfoxide reductase) antioxidants. Healthy skin has an adequate antioxidant defense system aimed to reduce the amount of free radicals. In old skin or in skin under oxidative stress, this defense system can be depleted.
“At this point we don’t have anything effective at blocking visible and long-wave UVA light, but we can use antioxidants to neutralize any free radical that’s been generated,” he said.
Sunscreens with antioxidants have a negligible impact in photoprotection, however, because antioxidants are unstable molecules. The free radical protection afforded by sunscreens is achieved mainly by the sunscreen filters and not from the antioxidants, Dr. Wang and colleagues have found.
Patients with skin of color who apply UVB-blocking sunscreen generate inadequate vitamin D. “We recommend people have their 25 hydroxyvitamin D level checked, and if low, consider supplementation,” he said.
It is imperative that healthcare professionals continue to educate all groups about the risk of excessive UV exposure, and how to minimize their risk, Dr. Wang said. Despite educational efforts by the AAD, only 30 to 40% of people use any type of photoprotection. “We have to come up with some ingenious easy convenient way to change behavior,” he said.
A study by Dr. Wang and co-investigators that assessed the effect of keeping sunscreen next to toothpaste found that study subjects who were instructed to keep their sunscreen next to their toothpaste used 20% more sunscreen at a 6-week measurement than those who were not instructed to do so. “Translated, that becomes almost twice as much sunscreen over the course of a year,” he said.