DENVER -- A new study revealed that men who ride motorcycles are at risk of impotence and urinary problems, possibly because the vibration of the engine damages nerves in their penises.

The study by doctors in Japan was published in the International Journal of Impotence Research.

It found that out of 234 motorcyclists who rode about three hours every weekend, 69 percent reported mild to severe erectile dysfunction.

Of the 178 motorcyclists with hard-padded saddle, 70 percent had erectile dysfunction. Of the 32 motorcyclists with soft-padded saddle, 63 percent had erectile dysfunction.

The study was based on a voluntary questionnaire.

The researchers concluded, "The vibration from motorbike may cause ED, and the degree of vibration to perineal lesion might be associated with the severity of ED."

The researchers also said more studies are needed to determine the cause of erectile dysfunction in motorcyclists.

The International Journal of Impotence Research Web site said The Journal of Sexual Medicine (IJIR) is celebrating 20 years of publishing excellence. IJIR publishes research on male and female sexual dysfunction, including important information related to cardiovascular disease, diabetes, menopause and vascular deficits.