This last week we've seen a good object lesson in that scientific adage: Correlation does not equal causation. In 2014, researchers released a study associating sildenafil use with melanoma in U.S. men. The scientists were cautious about drawing any direct causal relationship between the drug and the occurance of skin cancer, but the report was enough to stir up a bit of a scare. Some men undoubtedly stopped taking or decreased their use of Viagra because of it (and some probably reduced their sun exposure instead).
Now it seems to have been debunked by a doctor who decided to slice and dice the data a little differently.
Urologist Stacy Loeb of New York University took it on herself to look further into the data and the study, in part so she could know how to advise her own patients about the use of ED drugs. She was able to find comparable data about ED drug users from Sweden, which at first seemed to confirm the results of the U.S. study. The data from Sweden also included users of Levitra and Cialis.
However, when Loeb dug deeper, she found that the relationship between use of ED drugs and melanoma was not as simple as it appeared. When analyzing the data further, Loeb found that rates of melanoma did not increase with the amount or frequency of ED drug use, how many years patients had used them, or the half-life of the drugs (the amount of time they stay in the body). So if ED drugs weren't contributing melanoma, what was?
The apparent answer: socioeconomic status. Call it Lifestyles of the Rich and Virile. Men who can afford Viagra and other ED drugs have more disposable income and have lifestyles that in general put them at higher risk for developing melanoma -- Caribbean vacations, weekends on the golf course, you get the idea. (True, Sweden's healthcare system does cover ED drugs, but it uses a rationing system similar to other countries with national healthcare, so a steady supply would come out of pocket.)
This theory was reinforced when Loeb found similar rates of basal cell carcinoma (a sun-related skin cancer) in the patients with melanoma, indicating there were likely behavioral factors at play.
So what's the upshot of all this? Loeb says she now focuses on the well-established side effects and health risks of Viagra when counseling patients, since the link to skin cancer seems questionable, but does advise men to take standard precautions such as wearing sunscreen and getting moles checked. Good advice for anyone, regardless of whether you use an ED drug.
