THURSDAY, Dec. 15 (HealthDay News) -- If you're a woman who smokes and you are looking for another reason to quit, consider this: A new study has found a link between tobacco use and skin cancer.

The study found that women who had squamous cell skin cancer were more likely to have smoked than those who were free from the disease. And those who smoked at least 20 years were twice as likely to develop squamous cell skin cancer, a less aggressive form of skin cancer than melanoma.

Men who smoked had a modest risk for the two types of non-melanoma skin cancer -- basal cell and squamous cell cancer -- but the results weren't statistically significant, the study authors noted.

"We don't know why," said study lead author Dana Rollison, referring to the difference between women's and men's risk. Both men and women get a lot of exposure to the sun, the main risk factor for skin cancer, she noted.

But lung cancer research may offer a clue, said Rollison, an associate member in the Moffitt Cancer Center department of cancer epidemiology, in Tampa, Fla. Hormonal differences affecting the metabolization of nicotine and the body's ability to repair damage to lung DNA caused by smoking have been noted before, suggesting that the female hormone estrogen may play a role, she said.

The study, published online in the journal Cancer Causes Control, was done at the Moffitt Cancer Center and the University of South Florida, also in Tampa.

For the study, 383 patients with skin cancer were compared to 315 people without the disease. The participants were asked how much they smoked, when they picked up the habit and the total number of years they'd smoked. A total of 355 men and 343 women were included in the study. All were white, the group most at risk for skin cancer. Risks for both types of non-melanoma skin cancer were analyzed separately, compensating for the presence of other risk factors.

The researchers found that the more people smoked, the more likely they were to have skin cancer, Rollison said. Men who had basal cell skin cancer were significantly more likely to have smoked for at least 20 years than men with no cancer, the study authors noted.

While the study found an association between smoking and skin cancer risk, it did not prove a cause and effect.

Despite the elevated smoking-related risk among women, men overall are more likely to get skin cancer, Rollison noted. She said that "it is possible men's skin is more sensitive to sun exposure than women's."

But another skin cancer expert suggested that men may be less inclined to use sunscreen or other protection when outdoors.

"Although it could just be a genetic difference (between men and women), men tend to have more unprotected sun exposure in their lives," said Dr. Jeffrey Dover, associate clinical professor of dermatology at Yale University Medical School.

Dover said the study findings weren't surprising because "we know cigarette smoke contains carcinogens" and smokers are "blowing the smoke and ash around their faces all day."

The study is important, he added, because "although we have done well, we can do even better" at eliminating smoking as a cause of disease. "This adds more fuel to the idea that smoking has no place in our society."

Non-melanoma skin cancer is the most common form of cancer in the United States, where about 2 million cases are treated annually, according to the U.S. National Institutes of Health. Squamous cell cancer occurs in the epidermis, the top layer of skin, and can spread to other organs. Basal cell skin cancer occurs in the dermis, the skin layer beneath the epidermis. While it does not spread to other organs, it is far more common than squamous cell cancer, according to the government agency.

More information

To learn more about skin cancer, visit the U.S. National Cancer Institute.