The more sunburns you've suffered, the more likely you are to develop a type of skin cancer -- and the number of sunburns you've had is a stronger predictor than skin type of your cancer risk, according to a new report.
In a study of 107,900 predominantly white women who were followed for eight years, those who had six or more sunburns in their lifetime had more than twice the risk of developing squamous cell carcinoma than women who had never been burned.
As the number of sunburns in a lifetime increased, so did a person's cancer risk, the researchers reported today in the Journal of the National Cancer Institute.
"We found that the number of severe sunburns was strongly associated with the risk of squamous cell carcinoma, and far outweighed the importance of the tendency to sunburn or tan," reported Francine Grodstein, an instructor of medicine at the Channing Laboratory at Brigham and Women's Hospital in Boston.
Squamous cell carcinoma is one of the most common types of skin cancer, with about 100,000 new cases diagnosed each year in the United States. It can be cured if detected and treated early, Dr. Grodstein said.
While sun exposure is a known risk factor for squamous cell carcinoma, there has been little information on how much exposure raises a person's risk -- and how sunburns and skin type fit into the equation, Dr. Grodstein said.
In the study, a woman's complexion did affect her risk of the cancer -- those with light brown or red hair had twice the risk of squamous cell carcinoma as those with dark brown hair. But this risk factor was not as strong a predictor as the number of lifetime sunburns.
The report also showed that women who lived in Florida or California were at about twice the risk of those living in the Northeast. And after accounting for the number of sunburns, women who burned after two or more hours in the sun as children were 50 percent more likely to develop squamous cell carcinoma than those who never burned.
Smokers showed a slightly increased risk over women who had never smoked, the researchers found.
"We've had studies that show that the sun you get as a child increases your risk of melanoma," the deadliest form of skin cancer, said Dr. Darrell Rigel, a clinical associate professor of dermatology at New York University Medical School. "This now shows that it also increases your risk of squamous cell carcinoma."
This finding is important, because by protecting your children and yourself from sunburn, you can help curb the rapidly rising number of skin cancer cases in the United States, he said.
To protect yourself from skin cancer, use a sunscreen with a sun protection factor (SPF) of at least 15 when in the sun, advised Dr. Bruce E. Katz, an associate clinical professor in the department of dermatology at Columbia-Presbyterian Medical Center in New York.
In addition, moles should be checked once a year, particularly for people who spend a significant amount of time in the sun, he said. People with a family history of skin cancer should be checked every six months, Dr. Katz advised.