The study, published in the journal Cancer, looked at melanoma in about 60,000 Caucasian women ages 50 to 79, reported National Public Radio (NPR). (Researchers focused on light-skinned people because they're at the highest risk for this type of cancer.)
Over a 12-year period - and after controlling for risk factors like tanning and low use of sunscreen - women who took aspirin at least twice a week had a 21 percent lower risk of developing melanoma, researchers found.
"We're really excited aspirin could be used as a potential preventive agent for melanoma," study coauthor Jean Tang, M.D., of Stanford University Medical School, told NPR. "In terms of cancer prevention, a lower melanoma risk by 20 percent is very large and significant."
A 20 percent drop is significant, but to put things in perspective, only 548 women, or less than 1 percent of the 60,000, actually developed melanoma. A 20 percent overall decrease meant about 100 fewer women in the study got skin cancer. But if you consider that there are an estimated 50 million postmenopausal women in the U.S., aspirin may protect about 100,000 from getting melanoma.
The protection did appear to be cumulative - the longer the women took aspirin, the lower their rate of getting the potentially fatal skin cancer. Those who had used aspirin for one to four years had an 11 percent reduction in risk, as compared with 30 percent among those who had taken aspirin for five or more years, according to Time magazine.
This is the latest in a growing list of studies suggesting that inexpensive, over-the-counter aspirin lowers the risk of many cancers, including colon, breast, esophageal, stomach, prostate, bladder and ovarian, said NPR.
Still, the fact that there's an association between women who regularly take aspirin and a lower occurrence of skin cancer doesn't mean researchers understand exactly how or why aspirin seems to have this effect - or even if it really does.
Tang thinks it may be because aspirin reduces the inflammation that can cause cancer cells to grow more aggressive. Others surmise that aspirin's impact is linked to the drug's effect on platelets, the blood component that causes clotting, an effect that other anti-inflammatory medications like ibuprofen don't have.
But Eric Jacobs, Ph.D., an epidemiologist at the American Cancer Society, noted that the research on melanoma and aspirin has been mixed: "There've been about eight studies that have looked at melanoma, and about half of them find slightly lower risk, and half find no connection at all," he told NPR. He also warned that aspirin is "a real drug with real side effects. It can cause serious and even fatal stomach bleeding, even at low doses."
If your doctor OKs taking a small amount of aspirin regularly, Randall Harris, M.D., of Ohio State University, who has done research on aspirin and breast cancer, believes this regimen can have anti-cancer effects. "You don't need to take too much," he told NPR, just one tablet a couple of times a week.