Aging Biology

Sunscreens: Hype and Reality (repost 2007)

Sunscreens are helpful in reducing exposure to the harmful effects of UVA and UVB. These types of solar radiation contribute to the development of premature skin aging, wrinkling and both malignant and non-malignant skin cancer. Basal Cell Cancer and Melanoma, among other types of skin cancer has an increased incidence in sun exposed individuals. Some have estimated that only about 20% of melanomas are related to skin cancer. Other disfiguring cancers, including basal cell though seem to have a very high correlation with sun exposure.

Melanoma has multiple risk factors which include fair complexion, blonde or red hair color, blue, blue/green eye color (skin phototypes I/II), total sun exposure and a history of blistering sun burns. Genetics, or inherited risks may include genetically linked disorders such as the dysplastic nevus syndrome. The overall risk has increased dramatically over the last 50 years or so. In 1935 the lifetime risk for developing melanoma was 1:1500 in 1935 and grew to 1:74 in 2000. It is estimated that it will grow to 1:50 in 2010. It is estimated that over 53,000 new cases of melanoma are diagnosed now each year. A good number of these are diagnosed at an early stage.

Today’s New York Times implicitly criticizes Neutrogenia for a campaign in which they imply that not using sunscreen and their products is akin to suicide. It includes a clip in which a woman holds up a photo and says “My sister killed herself. She died of skin cancer.” Since melanoma can occur in people with little sun exposure and the majority of it may, this is in bad taste. There isn’t even a campaign that strong for lung cancer sponsored by Nicorette.

US regulatory agencies, including the FDA delayed for many years the approval of UVA protecting agents which had been widely used in Europe for many years. Mexoryl (Terephythalylidene Dicamphor Sulfonic Acid) in particular was long delayed. First approved in Europe around 1991, it only came to the US within the last year. Avobenzone, another compound with a broad UV coverage, degrades in certain conditions with sun exposure. In general you may look for the following compounds to obtain at least some UVA protection: avobenzone, octocrylene and oxybenzone. UVA protection does not have a defined measurement such as SPF.

Is it true that 80% of your sun exposure is obtained by the time you are 18? In this day of middle aged marathoners, ultra-marathoners, skiiers, and tria-athletes and young video gamers? Unlikely! Carl Bialik blogging at the WSJ notes that a more recent study purports that only 25% of lifetime sun exposure is obtained in the years before becoming an adult. Dianne Godar, writing as lead author of a paper in 2003 noted exposure measures approximately “23% of their lifetime UV dose by the age of 18. They get about 46% by the age of 40, and 74% by the age of 59” the rest comes over the remaining course of an individuals lifetime.Mick Jagger - Should Have Stayed Under The Boardwalk

The first line of prevention though, is avoidance of mid-day sun exposure. The next is covering yourself up in the manner of Zorro. Dark, absorbant clothes and a broad brim hat. And, since no one will do this, cover yourself well with sunscreen, before you go out the door, and then repeat periodically, particularly after getting wet. There really is no such thing as a waterproof sunscreen. Don’t forget your eye protection. UV protecting sunglasses can help prevent glaucoma, cataracts, macular degeneration and other eye problems.

Remember, if you don’t use protection in the sun, you could end up looking like Mick Jagger, and not have the same access to Botox.

1. Godar, D.E., Urbach, F., Gasparro F.P., and van der Leun, J.C. “UV Doses of Young Adults.” Photochemistry and Photobiology, 2003, 77 (4): 453–57.