TUESDAY, Nov. 21 (HealthDay News) --Marathoners face heightened odds for skin cancer, including melanoma, new European research shows.

The study "confirms things we already know," said Dr. Robin Ashinoff, chief of dermatologic, Mohs, and laser surgery at Hackensack University Medical Center in Hackensack, N.J. "We should be counseling these people to try and do their outside activities not when the sun is strongest, to wear a hat, T-shirt, long sleeves, and to put on sunblock. They're at high risk."

According to background information in the study, there is evidence to suggest that endurance exercise, including marathon running, may raise the risk of skin cancer. Not only are outdoor exercisers exposed to high levels of ultraviolet radiation, but endurance exercise may suppress the immune system.

"Anybody who spends a lot of time outdoors -- runners, bicyclists, golfers, tennis players -- all have a lot of sun damage," confirmed Ashinoff, who was not involved in the current study.

"People who spend more time in the sun have an increased melanoma risk," added Dr. Vijay Trisal, assistant professor of surgical oncology at City of Hope Cancer Center in Duarte, Calif.

Melanoma is one of the deadliest and most aggressive of all cancers. Other forms of skin cancer, such as basal cell carcinoma and squamous cell carcinoma, tend to be less deadly but can be disfiguring.

The study's Austrian authors, themselves avid runners, treated eight ultramarathon runners with malignant melanoma over the past decade. All of the melanomas were located on parts of the body that were not covered or were only partially covered by clothing during exercising.

For this study, the team from the Medical University of Graz recruited 210 marathon runners (166 of them men), aged 19 to 71, at a local marathon and compared them to a group of 210 controls recruited at a skin cancer screening campaign.

All participants were examined for skin cancer and completed a questionnaire about any personal and family history of skin cancer, sun sensitivity and sun exposure. Marathoners also answered questions about their training.

Controls were more sensitive to the sun (meaning they had lighter eyes and more sensitive skin types). But the marathoners had more dysplastic nevi (atypical moles, which can become malignant melanoma) and more liver spots. The more intense the training regimen, the more pronounced the abnormalities.

As a result of their participation in the study, 24 marathoners and 14 people in the control group were referred to dermatologists for possible non-melanoma skin cancer.

Most of the marathoners (96.7 percent) said they wore shorts and short-sleeved or sleeveless shirts. Only 56.2 percent said they regularly used sunscreen while training or competing, while 41.9 percent said they used it occasionally, and 1.9 percent said they did not use it at all.

Marathoners and other outdoor exercisers should follow some common-sense rules, Trisal said, such as "don't go out at midday, wear a wide-brimmed hat and a sunscreen of more than 15 SPF."

"Everything that makes you happy and feel good is, to some extent, good for your health. However, it is now well established that endurance exercise, and in particular marathons/ultramarathons, represent emergency states for the whole body," said Dr. Christina M. Ambros-Rudolph, study lead author and a dermatologist with the Medical University of Graz.

"Taking sunscreen alone is not enough as it can lose its power with sweating. It would be important to avoid training in sun-peak hours (11 a.m. to 3 p.m.) and wear reasonable gear that covers shoulders and upper back," she added.

Ambros-Rudolph and her colleagues are currently finishing a follow-up study.

More information

For more on skin cancer, head to the U.S. National Cancer Institute.