KEY POINTS:
Marathon runners face a heightened risk of skin cancer, likely due to more sun exposure or an immune system inhibited by arduous exercise, say researchers.
Dr Christina Ambros-Rudolph and colleagues at the Medical University of Graz in Austria studied 210 male and female marathon runners and 210 other people of the same age and sex.
The marathon runners were found to have more atypical moles - larger than common moles, with irregular and poorly defined borders. They also had more so-called liver spots - small, flat, brownish harmless lesions also known as solar lentigines.
The number of these moles and liver spots is considered a strong independent indicator of increased risk for developing malignant melanoma.
Writing in the journal Archives of Dermatology, the researchers said this was particularly pronounced in the runners who trained at the highest levels of intensity.
The marathon runners had a higher risk for both malignant melanoma and non-melanoma skin cancer, the researchers said.
Melanoma occurs in the cells that produce pigment and is the leading cause of death from skin disease. Only 56 per cent of the runners said they regularly used sunscreen.
"They should reduce UV [ultraviolet radiation] exposure during exercising by choosing training and competition schedules with low sun exposure, wearing adequate clothing, and regularly using water-resistant sunscreens," wrote the research team, which included two marathon runners.
Marathon running has become more popular in recent decades.
The researchers said in the course of training and competing outdoors, marathon runners might be exposed to considerable ultraviolet radiation from the sun, the primary environmental risk factor for melanoma.
Endurance exercise like running marathons - 42.2km long - or even-longer "ultra-marathons" might suppress the body's immune system and raise the likelihood of developing malignant melanoma.
The study involved 166 men and 44 women aged 19 to 71, recruited at the annual marathon in Graz. They were compared with the same number of people recruited at a skin-cancer screening campaign.
Twenty-four of the runners and 14 people in the control group were referred to dermatologists for surgical treatment of skin lesions suggestive of non-melanoma skin cancer.
The World Health Organisation estimates between two and three million people develop non-melanoma skin cancers and 132,000 are diagnosed with melanoma globally each year.
It estimates that 48,000 people die worldwide annually from malignant melanomas and 12,000 from other forms of skin cancer.
- REUTERS
