Psychology Today Do UV Tanning Beds Really Prolong Lifespan? "Beware of wild media extrapolations of scientific research reports."
The Daily Telegraph article reports on a recent scientific paper published by researchers from the University of Edinburgh. The paper concludes that outdoor exposure to higher levels of natural ultraviolet light in sunlight, and the use of indoor ultraviolet tanning beds, are associated with reduced mortality from heart disease and cancer.
The fundamental flaw in this conclusion is that sunlight is comprised of a broad spectrum of light, including invisible ultraviolet, all the spectral color wavelengths of visible light, and invisible infrared light. Sun-seeking behaviors such as spending more time outdoors, or living in lower latitudes, increase exposure to all of these spectral wavelengths, not just ultraviolet light.
So, to claim these effects are due specifically to the exposure to the ultraviolet short wavelengths in sunlight is overreaching. The authors could have just as easily concluded that the effects were due to green or orange wavelengths, which are also increased in intensity in people with sun-seeking behaviors.
How can the reported reduced cancer and heart disease mortality in indoor tanning bed users be explained? Does that indicate, as the authors suggest, that the ultraviolet component of the solar spectrum is responsible for the increased lifespan?
There is another, much more likely, explanation. It is well established that ultraviolet tanning bed users are also the most active sunseekers. They spend more time outdoors in sunlight, have more outdoor hobbies, and suffer more sunburns than people who never use tanning beds. So, in other words, these sunbed users are more exposed to all the visible and non-visible wavelengths in sunlight—and not just ultraviolet light.
Wow, confounding factors and unintended consequences. Whoda thunk!
The Wombat has Rule 5 Sunday: Enthusiasm! ready and waiting at The Other McCain.
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