Some of the highest rates of melanoma are in landlocked states with a relatively low ultraviolet (UV) index, including Minnesota, according to a study published Monday in the International Journal of Cancer.
The study found that Utah has the highest rate of melanoma attributed to UV radiation exposure, followed by Vermont, Delaware and Minnesota.
Melanoma, the most serious and aggressive form of skin cancer, used to be rare. But in recent decades, its incidence has increased faster than almost any other type of cancer. Between 2006 and 2015, for example, the rate at which people in the United States were diagnosed with the disease climbed an average of 2 percent each year in both men and women.
This year, more than 100,000 Americans will be diagnosed with the disease, and about 6,800 people will die of it.
Although some melanomas are not related to UV radiation exposure, most are. In the United States, more than nine out of 10 cases diagnosed can be attributed to UV radiation exposure, either from the sun or from tanning lamps and beds, the new study reports.
That figure is highest among non-Hispanic whites.
Yet many people seem to be in denial about how their exposure to the sun puts them at risk. That may be particularly true in states like Minnesota, which is a northern, landlocked state with a relative low UV radiation index, but whose residents still spend a great deal of time engaged in outdoor activities — or using tanning beds or lamps.
Using historical data
The authors of the current study — a team led by Dr. Farhad Islami, scientific director of surveillance research for the American Cancer Society — wanted to determine the state-by-state number, proportion and incidence of melanomas that can be attributed to UV radiation. They hope this information will help inform both residents and policymakers across the country to take more effective steps to protect against the disease.
To find out what proportion of the current rate of melanoma can be attributed to UV exposure in each state, the researchers needed to have something to which to compare it. They decided to use as their baseline — their reference point for minimum UV exposure — the melanoma incidence rates from 1942 to 1954 in Connecticut, which had the first statewide population-based cancer registry in the country. Connecticut is also a high-latitude state with a relatively low UV radiation index. Melanoma cases in the 1940s and 1950s would reflect UV exposure in the 1930s or earlier, when outdoor activities were less common and when people tended to cover more of their bodies while outside than they do today.
“Indeed, prior to substantial increases during the last 5 decades, melanoma incidence rates in Connecticut were low” — less than 2.3 per 100,000 people before 1955, Islami and his colleagues point out.
What the data revealed
When the researchers compared that historical data to 2011-2015 data, they found that UV exposure currently accounts for 91 percent of all melanoma cases in the United States — a figure that jumps to 94 percent of cases when the calculation includes only non-Hispanic whites.
The melanoma incidence rate was found to be 1.0 per 100,000 for blacks, 4.5 per 100,000 for Hispanics and 17.2 per 100,000 for non-Hispanic whites.
The five states with the highest UV-attributable incidence rates among all residents were the following:
- Utah: 36.3 cases per 100,000
- Vermont: 31.1 per 100,000
- Delaware: 28.2 per 100,000
- Minnesota: 27.6 per 100,000
- New Hampshire: 27.2 per 100,000
The researchers also calculated the melanoma incidence rates just for non-Hispanic whites in each state rather than for the entire population. That’s because some states’ lower rates could reflect the fact that they have higher proportions of nonwhite residents, who are less at risk for melanoma.
These non-Hispanic white incidence rates varied from 15.1 per 100,000 in Alaska to 65.1 per 100,000 in Hawaii. Several of the states with the highest rates are famous for their beaches:
- Hawaii: 65.1 cases per 100,000
- Delaware: 37.1 per 100,000
- Georgia: 36.5 per 100,000
- California: 33.8 per 100,000
- Maryland: 32.6 per 100,000
But several landlocked states also had high rates, including Minnesota:
- Utah: 40.4 cases per 100,000
- Vermont: 31.4 per 100,000
- Minnesota: 27.9 per 100,000
- Idaho: 27.6 per 100,000
- Kentucky: 25.7 per 100,000
These numbers indicate that “the UV index is not the only determinant of sun exposure intensity, as indicated by high sunburn prevalence in many states with relatively low UV index, such as Minnesota and Idaho, where about 50% of whites [aged 18 and older] in 2004 reported having at least one sunburn during the preceding year,” the researchers write.
“High prevalence of outdoor activities (e.g., going to beaches, lakes, or outdoor swimming pools; recreational boating; skiing; and perhaps occupational activities such as farming) and insufficient sun protection are likely major contributors to the high UV-attributable melanoma rates even in states with low UV index,” they add.
The importance of prevention and early diagnosis
Melanoma is largely preventable, but it requires us to recognize that tanning is not healthy, but rather a sign of damaged skin.
To lower the risk of melanoma (as well as other forms of skin cancer), prevention is key — for people of all skin tones. That means avoiding direct sunlight as much as possible and using sunscreens and other forms of sun protection when outside.
Early diagnosis and treatment is also important. Check your skin regularly for signs of the cancer. And if you find something suspicious on your skin, see a doctor promptly.
“The burden of UV-attributable melanoma is considerably high in all states, underscoring the need for broad implementation and enforcement of preventive measures across states to reduce UV radiation exposure from excessive sun exposure and indoor tanning, with priority for states with a higher burden,” the researchers conclude.
FMI: You’ll find an abstract of the study on the International Journal of Cancer website, but the full paper is behind a paywall.