MONDAY, June 6 (HealthDay News) -- People with Parkinson's disease may have twice the risk of developing the deadly skin cancer melanoma, a new report confirms.
Parkinson's disease, which affects about one million people in the United States, is a progressive neurological disorder that causes tremors, stiffness and difficulty with movement, coordination and walking. Melanoma, with nearly 70,000 new cases diagnosed each year in the United States, is the most dangerous type of skin cancer.
"Over the past decade there has been accumulating evidence that Parkinson's disease patients are less likely to have most types of cancers, particularly smoking-related cancers; however, they were more likely to have melanoma," said lead researcher Dr. Honglei Chen, head of the Aging & Neuroepidemiology Group at the U.S. National Institute of Environmental Health Sciences.
Not only are people with Parkinson's disease more likely to develop melanoma, but people with melanoma are more likely to develop Parkinson's disease. "It appears the association is bidirectional," he said.
Scientists have theories about why these conditions seem to co-occur, but no firm answers. They know it's not the drugs Parkinson's patients take, Chen said.
"Both conditions may have common genetic pathways or environmental factors or both," he said. "We understand very little about this possible relationship."
Ultraviolet radiation from the sun can cause skin cancer, including melanoma. No association was found between Parkinson's disease and skin cancers other than melanoma, however, the investigators said.
The report, which was supported by the National Institute of Environmental Health Sciences, is published in the June 7 issue of Neurology.
For the study, Chen's team analyzed 12 epidemiologic studies dating from 1965 through 2010 that looked at a possible association betw
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