For years, sunscreen and antioxidants have been advocated to prevent photoaging of skin, but to date, there has been no scientific evidence to back up such claims other than studies on hairless mice and one 35-patient trial of patients with a history of skin cancer that evaluated sunscreen's effect on histologic skin aging.
Now, new research(annals.org) in the June 3 issue of Annals of Internal Medicine supports the claim that applying sunscreen while outdoors retards skin aging in healthy middle-aged men and women.
Using a community registry in Nambour, Australia, 1,621 adults were randomly chosen, of whom 903 were younger than age 55 and, thus, eligible for the study. These participants were randomly assigned to one of four groups using the following protocols:
- daily use of broad-spectrum sunscreen and 30 mg of beta-carotene,
- daily use of sunscreen and placebo,
- discretionary use of sunscreen and 30 mg of beta-carotene, and
- discretionary use of sunscreen and placebo.
Based on microtopographic evaluations performed by assessors blinded to participants' treatment allocation, the study authors concluded that the combined daily sunscreen groups showed no detectable increase in skin photoaging after 4.5 years, with aging from baseline to the end of the trial coming in at 24 percent less for the daily users versus the discretionary user groups. Beta-carotene supplementation demonstrated no discernible effect on skin aging.
"We have shown that regular application of sunscreen by people younger than 55 years for 4.5 years significantly retarded aging of the skin," the authors wrote. "This difference does not seem to be due to changes in outdoor behavior or sun protection by the intervention compared with the control group.
"Long-term beta-carotene supplementation seemed not to influence progressive skin aging, although we could not rule out a small decrease or increase in skin aging as a result of supplementation."
According to the authors, the clinical implications of the study are important because data show that "a unit increase in microtopography (grade) significantly correlates with risk for actinic keratoses and skin cancer," as well as visible deterioration in the skin.
"A reduction in the highly prevalent aging changes among middle-aged adults by regular application of sunscreen will, therefore, be associated with cosmetic benefit (prevention of visible aging changes and hence more youthful appearance) and reduced risk for skin cancer," the authors wrote.
"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."