Melanoma is a malignant form of skin cancer, and it is associated with sun exposure, to what extent researchers are still trying to discover. Paradoxically, past studies have shown that indoor workers have an increased risk compared to outdoor workers.
It’s also been suggested that high vitamin D levels might have some protection against melanoma and melanoma progression, but this has yet to be confirmed in high quality studies. If this were true, coupled with the evidence that outdoor workers have a decreased risk of melanoma, then the most prudent advice may be to seek moderate sun exposure as opposed to no sun exposure or overexposure.
In a recent ecological study, researchers have found a relationship between UV radiation and melanoma that might also fall in line with the above evidence and line of reasoning.
Researchers gathered data on registered cases of melanoma in Austria from 1990 to 2010. They also collected census data on the Austrian population from 1971, 1981, 1991 and 2001. The researchers looked at incidence of melanoma and mortality from melanoma in relation to:
- Altitude. The higher the altitude, the more prevalent and intense UV radiation is.
- Year of diagnosis and death from melanoma. There has been a general trend of more UV radiation on the ground level due to climate change.
- The amount of people living in urban versus rural environments. In general, there is more UV radiation in rural environments.
When they looked for trends in melanoma and its relation to the above factors, here is what they found:
- In all years except 1990, age-adjusted incidence significantly increased with altitude and there was an estimated 0.5 – 1% increased risk per 10 meters. The suggestion here is that more UV leads to higher incidence of melanoma.
- Approximately a 3% increase in incidence per 10 meters in the age group below 30 years old.
- Melanoma risk was higher in urban districts compared to rural districts, which can be considered a somewhat paradoxical finding.
- Interestingly, deaths from melanoma decreased with increasing altitude and were more likely in Vienna, the largest city in Austria.
So what does this mean? The researchers found that UV may increase incidence of melanoma, but decreases risk of death from melanoma. They speculate,
“Living in urban areas compared to rural areas in Austria is associated with a substantially higher melanoma risk that could be caused by intermittent UVR exposure patterns. Further, we found increased melanoma incidence, but not mortality rates for Austrian inhabitants living at higher altitudes. A possible explanation of this discrepancy could be that UVR induces melanoma, but also slows down tumor progression by means of elevated serum vitamin D levels.”
So the suggestion is that while UV may be related to melanoma, its help in inducing vitamin D production also protects against a poor prognosis of melanoma and rare subsequent cases of mortality. Further explanation may be that there is better care happening in higher altitudes, as those communities tend to be smaller and individuals could have better communication with a local specialist.
More studies should clarify the role of UV in melanoma, as it is complex and uncertain for the time being. The Vitamin D Council does recommend moderate sun exposure as opposed to no exposure or overexposure, because taking multiple diseases into account, not just skin cancer, it’s apparent that sun exposure offers protection against a wide array of diseases.