If a picture says a thousand words, then a new study showing just how damaging years of smoking can be on the skin speaks volumes.

The study used photos of identical twins, one of whom who smoked and one of whom either didn't, or quit smoking long before the other.

In the pictures, smokers show more premature facial aging than their non-smoking siblings, with more bags under their eyes, more tiny wrinkles around their mouths, and deeper wrinkles in the smile lines around their mouths.

The pictures appear in the November issue of Plastic and Reconstructive Surgery, the medical journal of the American Society of Plastic Surgeons.

Study author Dr. Bahman Guyuron, from the department of plastic surgery at University Hospital Case Medical and Case School of Medicine in Cleveland, Ohio, says the study helps show that even smoking just a few years longer than a sibling can result in more aging of the skin.

"It is noteworthy that even among sets of twins where both are smokers, a difference in five years or more of smoking duration can cause visibly identifiable changes in facial aging," Guyuron and his coauthors write.

Research has shown that smoking appears to impair the skin's mechanisms to repair itself. The authors say smoke appears to alter the turnover of cells in the skin by down-regulating its ability to synthesize collagen and elastin.

For the study, researchers went to the annual Twin Days Festival in Twinsburg, Ohio, between 2007 and 2010, where they found pairs of identical twins who differed by smoking history.

In each pair, either one twin smoked and the other did not, or one twin smoked at least five years longer. The twins completed questionnaires about their medical and lifestyle histories, while a professional photographer took close-up photographs of each twin's face.

The researchers selected only twin pairs who were similar in weight as well as the environmental factors that can affect facial aging, including sunscreen use, alcohol intake, and work stress.

Without knowledge of the twins' smoking history, plastic surgeons then analyzed the twins' faces, looking for "specific components of facial aging" that are typically affected by smoking.

In almost every case, the surgeons were able to identify the smoking or longer-smoking twin, simply based on the differences in facial aging as shown in the photographs.

Most of the differences affected the middle and lower thirds of the face. While there were few differences in aging of the forehead lines or "crow's feet" around the eyes, the smokers had more sagging of the upper eyelids, as well as more bags of the lower eyelids and under the eyes.

The smokers also had more pronounced nasolabial folds, which are the laugh lines between the nose and mouth. They also had more wrinkling of the upper and lower lips and sagging jowls.

Among twins with more than five years' difference in smoking history, the twin with the longer history of smoking had worse scores for bags on the lower lids and under the eyes and lower lip wrinkles.