A study from Austria has shown that marathon runners are at increased risk of both melanoma and non-melanoma skin cancers.
In this study, which was published in the November 2006 issue of the medical journal Archives of Dermatology, researchers examined the skin of 210 marathon runners and 210 non-runners who were matched to the runners for age and sex. The researchers found that the runners had a larger number of suspicious moles and other skin abnormalities suggestive of an increased risk of skin cancer than the non-runners did.
The increased risk of skin cancer in the runners was probably due primarily to their extensive exposure to sunlight during lengthy outdoor training runs. Most of the runners wore only running shorts and sleeveless or short-sleeved shirts while running, leaving much of their skin exposed to the sun, and only about half of them used sunscreen regularly.
Another factor that may increase marathon runners' risk of skin cancer is weakening of the immune system. Very intense athletic training, such as preparation for marathons, has been reported to impair immune function. Impaired immune function is associated with an increased risk of some types of skin cancer, including melanoma.
Although marathon runners may be an extreme case, athletes who participate in other outdoor sports are also at increased risk of skin cancer. Athletes in many sports train and play in the midday sun, when exposure to ultraviolet light is greatest. The situation is made worse by the fact that athletic activity causes sweating, which reduces the amount of ultraviolet light needed to damage the skin and can wash off sunscreen.
The American Academy of Dermatology recommends that people stay out of the sun between 10 a.m. and 4 p.m., when the sun's rays are the strongest. Athletes who must train or play during these peak sun hours should wear protective clothing, such as a hat with a brim and long-sleeved shirts, and should wear sunscreen on the exposed parts of their bodies. Because sunscreen can be washed off by sweat, it is important to reapply sunscreen frequently while exercising.