The study involved 900 white people ages 25 to 55 in Australia, where intense sun exposure is a fact of life. Most had fair skin, and nearly all burned in the sun. Most were using sunscreen at least some of the time, and two-thirds wore hats in the sun.
But researchers wanted to find out what would happen to skin if people tried to use a broad-spectrum sunscreen all the time over four and a half years. Half of the study participants were told to continue their usual practices, and the other half to slather on sunscreen daily.
The result, the researchers reported on Monday in The Annals of Internal Medicine, is that those assigned to use sunscreen every day had noticeably more resilient and smoother skin than those assigned to continue their usual practices.
The study also included nearly 900 people who were randomly assigned to take beta carotene, a nutritional supplement, or a placebo to see if the supplement prevented skin aging. It did not. ...
The study does not answer the question of whether people older than 55 would also have more youthful skin if they used sunscreen, Dr. Green cautioned. After 55, she said, aging’s effects on skin start to predominate. And the effects of ultraviolet light on skin are cumulative.
--Gina Kolata, NYT, on evidence supporting following Asian mothers' mandate to their daughters