Here is the study citation:
Hughes, M. C. B., Williams, G. M., Baker, P., Green, A. C. (2013). Sunscreen and prevention of skin aging: A randomized trial. Annals of Internal Medicine, 158(11), 781-790. doi: 10.7326/0003-4819-158-11-201306040-00002
The study took place in Australia and involved about 900 adults who were under the age of 55. The authors noted, and I found interesting, that having old looking skin when you are under age 55 is related to the affect of the sun only, not that of the sun and getting old.
Otherwise and to be honest, the research design in this particular study was hard for me to follow.
People in the study were randomly assigned to one of two or four conditions (my confusion). The study was not just about sunscreen and aging. The researchers also wanted to know if taking a beta carotene supplement would reduce the signs of photoaging. It looks like people were assigned to a group where they were asked either to apply sunscreen every day (and they were supplied with the sunscreen) or to use sunscreen on their own and at their will. These same people (2 groups) or more people (4 groups) were assigned (blindly) to take beta carotene pills every day or to take a placebo pill. In other words, the people did not know which pill they were taking. I can't tell if the people in the sunscreen group were the ones randomly assigned into pill groups. It would make more sense to have 4 groups, but then it would also make more sense to report it as two separate studies. However, the pills didn't help and they are not the point of this blog.
The main point is that no one was assigned to a no sunscreen group (because that would be unethical) and more importantly, no one was assigned to a lotion only group.
All the people in the study were assessed for the signs of aging in 1992 before they began the study and most of them were assessed again four years later. The assessment consisted of a visual exam of the skin on their hands. The exam was done by trained professionals and they graded the skin on a scale from 1 to 6. People in the daily sunscreen group had lower grades on this visual inspection than those in the other groups - at the second time. Lower grades are good. There was no difference in the grade for those who took the supplements. (They also answered questions about their daily sun and other lifestyle habits).
I am 100% in favor of sunscreen and I do believe that it prevents damage from both UV A and B rays. From this study alone, I am not convinced that sunscreen is as effective or more effective than body lotion for preserving a youthful skin appearance.
I am especially baffled by using the hands as the assessment. It would seem that the face would get more sun exposure and that the hands would tend to get washed a lot during the day so as not to be truly 'sun screened.'
I have youthful skin - so say I :). I attribute mine to stopping smoking many years ago, eating healthy, getting daily exercise (blood and oxygen flow) and by applying body lotion from my head to the bottom of my feet every single day - because my Mom told me to.
So wear your sunscreen, hats and glasses but do these other things as well.