Researchers at the Mayo Clinic are attempting to allege that indoor tanning is causing an 8-fold increase in melanoma incidence since 1970 in women under age 40 in one Minnesota county despite the fact that the nation’s largest and most comprehensive cancer registry shows no such increase.

Slated to be published Monday, April 2 in the journal Mayo Clinic Proceedings, Mayo dermatologists mined data retrospectively in Olmsted County, Minn. — the county home to Rochester, the Mayo Clinic and an inordinate number of doctors per capita — from that county’s cancer registry. In a media advisory issued this week, Mayo alleges that melanoma incidence has increased 8-fold in young women in Olmsted County, Minn. since 1970 and 4-fold in young men.

“Even as the rates of some cancers are falling, Mayo Clinic is seeing an alarming trend: the dramatic rise of skin cancer, especially among people under 40,” the Rochester, Minn., health center said in a press statement. “According to a study by Mayo Clinic researchers published in the April issue of Mayo Clinic Proceedings, the incidence of melanoma has escalated, and young women are the hardest hit.”

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The problem? Mayo’s statements are directly contradicted by The National Cancer Institute’s national data, a much larger, more-diverse multi-city database which shows a slight decrease in melanoma incidence in women under 20 since 2000 and rates of about 0.5 per 100,000 — or 5 cases in 1 million women under 20. In fact, the National Cancer Institute’s melanoma data for women under age 49 shows decreasing rates since the mid-1980s, with large increases in men over age 50.

“It’s hard to imagine this being anything but intentionally misleading to suggest that melanoma is rising ‘especially’ in young women when the national data are very clear that it is increasing dramatically in older men, not in younger women,” Smart Tan Vice President Joseph Levy said. “To say that women are ‘hardest hit’ just repeats that error. It’s politics — not science.”

In an online press conference Wednesday, the Mayo team alleged that NCI’s database is too large and cumbersome and that the national program under-reports melanoma incidence. The team did not offer any explanation of why the NCI database actually shows a small decrease for young women in that timeframe or why mortality rates — always considered a better measure of real disease activity — are declining in young women, a measurable and divergent outcome.

“It’s pretty audacious for the Mayo dermatology group to suggest that one county’s data — raw numbers of reported incidence in a fair-skinned, ethnically homogeneous county with 5-40 times more pediatric specialists than other counties in Minnesota — is somehow more accurate than a national database,” Levy said. Levy has tracked melanoma data for 15 years, giving a presentation in 2004 to the American Society of Photobiology on the fact that melanoma is increasing in older men, but public health campaigns continue to be centered on young women.

“Even if the NCI database did under-report, the Mayo team does not offer any reason for why the national data doesn’t show the increase that they say exists in one county,” Levy said.

According to the Minnesota Department of Public Health, there are 48.8 pediatric specialists per 100,000 residents in Olmsted County — 5 times more than the Twin Cities (9.6) and more than 30 times what you find in Duluth (1.5). “More doctors per capita means more diagnosis,” Levy said. “That should be the default explanation for why Olmsted is different. It’s the most obvious explanation. This Mayo paper doesn’t acknowledge that at all.”

The American Cancer Society’s Cancer Facts and Figures also disagrees with the Mayo assessment. “During the 1970s the incidence rate of melanoma increased rapidly by about 6 percent per year,” ACS reported. “However, from 1981-2000, the rate of increase slowed to 3 percent per year and since 2000 melanoma incidence has been stable.” ACS, like NCI, also reports that melanoma mortality rates have been declining.

The story will be released Monday, when the journal article is published. Smart Tan will be sending material on the study in a Member Advisory and will work with the Indoor Tanning Association to assist industry lobbying efforts on this issue.