Before-and-after photos have their place and level of effectiveness for making points, but when you can compare how identical twins have aged — and use differences in smoking habits as the variable — one can hit scientific pay dirt.

Which is what researchers did, interviewing 79 sets of identical twins at the annual Twins Days Festival in (where else?) Twinsburg, Ohio; their findings were published in the latest issue of Plastic and Reconstructive Surgery, according to the Daily Mail.

As you might expect, when one identical twin smokes more than the other identical twin, the findings indicate that impact on visible aging is significant — even with as little as five years’ difference in smoking history.

Photos from Identical Twins Study That Indicate Smoking Accelerates Facial Aging

The left-hand twin is a nonsmoker; the right-hand twin smoked for 29 years — observe the differences in aging around the eyes. (Image source: American Society of Plastic Surgeons)

Smoking reduces oxygen to the skin, which also decreases blood circulation, which in turn can result in weathered, wrinkled, older-looking skin, says Dr. Bahman Guyuron, a plastic surgeon and the lead author of the study.

Also of note: Even if a person has smoked for a long time, quitting the habit can have a positive impact to his or her overall health, including visible skin damage.

Here’s some more visual proof, all photos via the American Society of Plastic Surgeons:

Photos from Identical Twins Study That Indicate Smoking Accelerates Facial Aging

The twin on the right is a smoker; the twin on the left is a nonsmoker — observe the more pronounced creases around her nose and mouth for the sister on the right.

Photos from Identical Twins Study That Indicate Smoking Accelerates Facial Aging

The left-hand twin has smoked 17 years longer than the right-hand twin; observe the differences in lower-lid bags and upper and lower lip wrinkles.

Photos from Identical Twins Study That Indicate Smoking Accelerates Facial Aging

These identical twins both smoked, but the right-hand brother smoked 14 years longer than the left-hand brother.

(H/T: Daily Mail)