研究：防曬霜能延緩皮膚老化

最近發表在美國《內科學年鑑》上的一份研究報告指出，每天使用防曬霜可延緩皮膚因光照老化的進程，同時降低患皮膚癌的風險。研究人員將903名年齡在55歲以下的被試者隨機分成四組，其中兩組每天使用防曬霜，但有一組還會服用β胡蘿蔔素；另外兩組只是在被試者認爲有必要的時候才使用防曬霜，也有一組服用β胡蘿蔔素。研究人員對被試者追蹤研究四年半以後發現，每天使用防曬霜的兩組被試者皮膚光老化的程度比偶爾使用防曬霜的被試者輕24%，而且各年齡段均無差別。研究人員還指出，一向被認爲有抗衰老功能的β胡蘿蔔素在研究中沒有表現出明顯功效。

皮膚美容學家建議，早晨出門前要在臉、頸、手等直接被太陽照到的地方塗防曬霜，並且過段時間後要記得重新塗抹；就算一整天都待在室內，也應該使用防曬霜。另外，在使用防曬霜的同時，也要採取其他防曬措施，比如穿長袖衣服、戴寬檐帽、避免在上午十點到下午2點太陽光最強烈的時段出門等。

A new study has found that applying sunscreen every day can do more than lower your risk of skin cancer — it can also drastically reduce the effects of photoaging, or the way frequent sun exposure can make your skin look older. And there's more good news: Even if you slacked off on sunscreen in your youth, middle age isn't too late to benefit from slathering it on.

"It has been a source of frustration for us that for some sections of the community, the sun-safe message does not seem to be getting through," Dr. Adele Green, a professor at the Queensland Institute of Medical Research at the University of Queensland in Australia, said. "We now know that protecting yourself from skin cancer by using sunscreen has the added bonus of keeping you looking young."

The study, published this week in the Annals of Internal Medicine, also looked at whether taking beta-carotene supplements could have an anti-aging effect. Beta-carotene is a type of antioxidant known as a carotenoid, and has been linked to a reduced risk of skin cancer.

For the randomized-controlled trial, the researchers assigned 903 participants to one of four groups: Those who used broad-spectrum sunscreens daily and take 30 milligrams of beta-carotene, those who used daily sunscreen and took a placebo, those who took the beta-carotene but only used sunscreen periodically, and those who used sunscreen periodically and took a placebo. (All participants were age 55 or younger; the researchers decided it would not be ethical to have a group in which participants used no sunscreen at all.)

The two daily sunscreen groups used UVA/UVB blocking products with a SPF (sun protection factor) of 15 or higher; they applied the product to their head, neck, arms, and hands each morning after bathing, and reapplied it every few hours. The other two groups applied sunscreen where and when they thought they needed it.

The researchers tracked participants for four and a half years, and used putty-like skin molds to document fine lines and wrinkles. They found that the groups using sunscreen every day showed 24 percent less skin photoaging than those who only applied it periodically. The results were the same regardless of age, so even the middle-aged participants benefited from regular sunscreen use.

"The cost-effectiveness of promoting daily sunscreen use based on skin cancer prevention alone is probably substantially higher after accounting for the additional prevention of skin photoaging," wrote the researchers in their report.

Taking beta-carotene had no overall effect on skin aging, the researchers added.

In 2012, the U.S. Food and Drug Administration decided that sunscreen makers could state on the labels that their products reduced the risk of skin cancer and skin aging if used as directed, as long they also advised people to take other precautions, like reapplying sunscreen at least every two hours (more often if you're sweating or swimming), avoiding going out when the sun is most intense (usually between 10 a.m. and 2 p.m.), and wearing long-sleeved shirts, pants, and broad-brimmed hats to shield the skin when possible.

If you only have a few minutes in the morning, it makes sense to apply sunscreen to the areas most likely to see the sun — your face, neck, and hands. All types of sunscreen, even "sport" or "waterproof" formulas, need to be reapplied regularly, and you should wear sunscreen even if you spend all day driving or working indoors, advises Dr. Jaliman, the cosmetic dermatologist.