Findings of earlier studies suggest that erectile dysfunction drugs may help reduce the risk for prostate cancer, the most common non-skin cancer among American men.

The results of a new research, however, have shown that the rate of prostate cancer diagnosis was the same for people who were prescribed drugs for erectile dysfunction as those who do not use them.

Erectile dysfunction, or impotence, affects about 5 percent of 40-year-old men and between 15 percent and 25 percent of 65-year-olds. Doctors may recommend several treatment options such as therapy, lifestyle changes and medicines to men suffering from impotence.

A range of phosphodiesterase type 5 inhibitor (PDE-5is) drugs, which include sildenafil, tadalafil and vardenafil, are available for treating the problem.

Some studies involving lab mice have suggested that these drugs may have anticancer effects, but there is not enough evidence of such beneficial effect on humans.

Because of the routine use of PDE-5i and the possibility that these erectile dysfunction drugs may have anticancer activity, Stephen Freedland, from Cedars-Sinai Medical Center, and colleagues set out to test the link between using this drug and the risk for prostate cancer.

"In vitro mouse studies have suggested that these drugs might have some anticancer activity, but the evidence in human subjects is mixed," said Freedland.

For the study published in the Journal of Urology on April 2016, Freedland and colleagues followed 6,501 men for a period of four years. Of these men, 364 were using PDE-5is drugs.

Over the course of the study, 19.5 percent of the men prescribed with erectile dysfunction drugs were diagnosed with prostate cancer. The rate was 22.7 percent in men who were not prescribed the drugs, a difference that the researchers considered as statistically insignificant.

The difference remained statistically insignificant even when Freedland and colleagues looked at men in North America, where use of the erectile dysfunction drugs is more prevalent.

"PDE-5i use was not associated with decreased prostate cancer diagnoses on post-hoc analysis of REDUCE," the researchers wrote in their study.

"In North American men, who had much higher baseline use of PDE-5i, this treatment was associated with an inverse trend of prostate cancer diagnosis that approached but did not reach statistical significance."

Figures from the U.S. Centers for Disease Control and Prevention (CDC) show that as of 2013, more than 176,000 men in the U.S. were diagnosed with prostate cancer, and more than 27,000 died because of the disease.