Using data collected from people aged 40 to 60 living in Minnesota’s Olmsted County, the Mayo Clinic researchers found that the overall incidence of melanoma increased nearly eightfold from 1970 to 2009.
The rise was most striking among women. Whereas the incidence of melanoma increased a worrisome 4.5-fold among the men in the study, it increased an alarming 24-fold among the women.
“I was quite shocked because I didn’t think it would be so dramatic in the middle-aged cohort,” said Dr. Jerry Brewer, a Mayo Clinic dermatologist and the lead author of the study, in a phone interview Tuesday.
The rise in the incidence of melanoma in younger adults — particularly young women — is well known. In fact, Brewer and his Mayo Clinic colleagues published a study in 2012 that reported an eightfold increase in the melanoma incidence among young women (aged 18 to 39) and a fourfold increase among young men between 1970 and 2009.
But no one has previously looked exclusively at the incidence of melanoma among middle-aged adults, which, as Brewer and his colleagues point out in their study, is “the fast-growing segment of our society.”
Included almost all of Olmsted County
Data for the study was provided by the Rochester Epidemiology Project (REP), a medical-records system shared by the Mayo Clinic and the Olmsted Medical Center. Almost 95 percent of the 144,000 residents of Olmsted County have given permission for REP to collect and use their medical records for research purposes.
From the data, Brewer and his colleagues identified 383 middle-aged adults aged 40 to 60 who received their first diagnosis of melanoma between 1970 and 2009. When broken down by decade, the researchers found that the incidence of melanoma had increased 7.6-fold during that period, with (as I’ve already noted) a 24-fold increase among women and a 4.5-fold increase among men.
The highest rates of increase were found in premenopausal women between the ages of 40 and 50 — higher than in any group that Brewer and his colleagues have studied so far. “Hormones may be a factor,” said Brewer. “That definitely needs to be studied.”
The data also revealed that the steepest increase in the melanoma rate occurred during the last decade examined by the study, 2000 to 2009. The Mayo Clinic researchers believe that finding may be related to the use of indoor tanning beds, which were developed in the mid-1970s and took off in popularity during the 1980s and 1990s.
“Going to a tanning bed once increases your [skin cancer] risk by 20 percent,” said Brewer. “And then every time you go after that in a calendar year, your risk increases by 2 percent.”
“It may take a couple of decades for the real effects [of indoor tanning] to catch up,” he added. “And that may be what we’re seeing in middle-aged women.”
A bit of good news
The data contained some good news: The overall likelihood of surviving melanoma increased by 7 percent during each year of the study.
Brewer believes those improved survival rates are most likely due to increased public awareness, which is leading to earlier diagnoses. “We just may be a little more likely to have our skin looked at, and so we may be catching [the cancer] earlier,” he said.
Indeed, most of the cancers identified in the Mayo Clinic study were diagnosed at either stage 0 disease (18 percent) or stage I disease (73 percent). The melanomas diagnosed during the 2000s also tended to be thinner and less invasive than those diagnosed during the 1980s — and thus easier to successfully treat.
Other researchers, however, have suggested that these thinner types of melanomas are actually “biologically benign” cancers and thus may represent an overdiagnosis of melanoma rather than a rising epidemic of the disease.
Brewer disagrees. “There is a controversy about whether we’re calling things melanoma today that we didn’t call melanoma 30 years ago,” he said. But, he added, the pathology slides of melanoma from three decades ago don’t look that much different from the slides examined in today’s labs.
“The diagnosis of melanoma under a microscope hasn’t really changed that much,” he said.
Furthermore, one-fourth of the melanoma-related deaths in the Mayo Clinic study occurred in people diagnosed with thin melanomas. (Of the 383 middle-aged adults diagnosed with melanoma in the study, 52 died from melanoma, 17 from other causes, and one from an unknown cause by the study’s final year of collecting data, 2009.)
Reducing your risk
The study, like all studies, has its limitations. Most notably, the majority of the population of Olmsted County is white and well educated, with ready access to health care. “Care should be taken when extrapolating the results of this study to other subpopulations in the United States,” write Brewer and his colleagues.
The Mayo Clinic researchers strongly recommend, however, that middle-aged people receive regular skin-cancer screenings. In addition, Brewer suggests that all of us take the following four simple steps to lessen the odds of developing skin cancer:
- Don’t use tanning beds.
- Use sunscreen whenever you’re outside.
- Familiarize yourself with your skin by performing frequent self-skin examinations.
- Check in with your dermatologist annually.
For more details about skin-cancer prevention, check out the tips on the American Cancer Society’s website. You’ll find the Mayo Clinic study, which was funded by the National Institutes of Health, in the January issue of the journal Mayo Clinic Proceedings.