Sunscreen helps prevent skin cancer. You know this. Now, however, scientists finally have proof for something else beauty editors have been telling us all along: SPF, when used often enough, also prevents wrinkles and signs of skin aging. How’s that for application motivation?

It’s true: Despite what you may have heard for years, there had never actually been any scientific proof — in terms of human clinical trials, that is — that sunscreen use had real effects on skin “age.” So researchers from Australia and the U.K. set out to test this hypothesis, by recruiting 903 participants under age 55 for a side-by-side comparison.

All participants underwent photoaging tests on the back of one hand at the start of the study, published yesterday in the Annals of Internal Medicine, and then were split into groups: Half were advised to use a sunscreen with SPF 15 or higher, every day, on their head, arms, neck and hands; the other half was told to use it on a “discretionary” basis.

After four and a half years, those who’d slathered on the SPF daily showed no detectable increase in skin aging. And overall, their aging scores were 24% lower than those in the SPF-whenever group! The study also tested whether the antioxidant beta carotene could help reduce skin aging (another commonly held belief), but the results found no differences between those who took supplements and those who took placebos.

What’s cool about this study is that the average participant age was 39; the researchers say this proves that even middle age is not too late to start a daily SPF routine and still see real results. Also, the aging tests were done on the backs of their hands — one place that I know I, personally, forget about on a daily basis (even though I’m really good at applying SPF moisturizer to my face every morning).

Doctor Lawrence Jaeger is a well known and respected board certified dermatologist and dermatologic surgeon who is the medical director of Advanced Dermatology Associates of New York. Doctor Lawrence Jaeger specializes in all aspect of medical, cosmetic and surgical dermatology.