And it concluded rather strongly that smokers' faces age faster than those of non-smokers. If you smoke, you look older than you would without smoking.
The study's abstract is published in the Journal of the American Society of Plastic Surgeons. And the study design was very clever: look at sets of identical twins in which one twin smokes and the other doesn't. Compare.
"Smoking twins compared with their nonsmoking counterparts had worse scores for upper eyelid skin redundancy, lower lid bags, malar bags, nasolabial folds, upper lip wrinkles, lower lip vermillion wrinkles, and jowls. ... Among twins with greater than 5 years’ difference in smoking duration, twins who had smoked longer had worse scores for lower lid bags, malar bags, and lower lip vermillion wrinkles."
This study has been turned into an online quiz by the New York Times. In its Well blog, you can compare photos of five sets of twins, and click on the photo of the one you think is the smoker. Give it a try.