The authors also found that prostate cancer risk seemed to decrease with higher durations of statin use.
Men taking statins were 15% less likely than non-statin users to have low-grade prostate cancer and 46% less likely to have high-grade cancer. Risks of low- and high-Gleason grade prostate cancer decreased with increasing cumulative duration and dose, according to the paper.
It isn’t yet clear why the statin-related risk reduction occurred only when men used the drugs for longer. Nor is it clear why the benefit from statins appeared more pronounced for prostate cancer of a higher Gleason score. More basic studies are needed to elucidate relevant mechanisms for those findings, according to Dr. Wang.
The authors addressed “healthy user bias,” which is a challenge when studying statin use and prostate cancer.
“In our case, the healthy user bias means statin users, who might use health services more frequently than non-statin users, possibly also have more opportunities for PSA screening and therefore have a decreased risk of high-grade prostate cancer. If this explanation holds, the risk of low-grade prostate cancer may increase among statin users,” Dr. Wang said. “But in our study, statin use was associated with decreased risk of both low- and high-grade prostate cancer. This indicates that the healthy user bias may not fully explain the observed association of statin use and reduced prostate cancer risk in our study.”
Although the healthy user bias might help to explain the higher prostate cancer risk among men who took statins for shorter durations. These patients are at early stages of lipoid screening and are more likely to be prescribed a PSA, the authors wrote.
A potential limitation to the study is that the authors selected the men based on urologic clinic visits rather than from the general population—a potential bias that might limit the findings’ generalizability, according to the paper.