Men who use condoms every time they have sex are less likely to harbor the virus that causes genital warts than those who are less consistent about protection, a new study finds.

The results, reported in the Journal of Infectious Diseases, may not sound surprising. However, some past studies have suggested that condoms may do little to protect men from infection with human papillomavirus, or HPV.

There are more than 100 strains of HPV, some of which cause genital warts. In most people, the immune system clears the infection fairly rapidly. However, persistent infection with certain HPV strains can eventually lead to cancer in some cases.

Persistent HPV infection is best known as the primary cause of cervical cancer, but it can also lead to cancers of the anus and penis.

Preventing HPV infection in men may help lower the odds of those latter cancers, and cut their chances of transmitting the virus to their female partners - potentially helping to prevent some cases of cervical cancer.

While condom use has been shown to lower the transmission of sexually transmitted diseases such as HIV, studies have yielded conflicting results as to whether condoms help lower men’s HPV risk.

One reason may be that HPV is easily transmitted, including any genital-to-genital contact, and some studies in which men have been tested for HPV in areas not protected by condoms have failed to show that condoms lower infection risk.

For the new study, researchers led by Carrie M. Nielson, of Oregon Health and Science University in Portland, tested 463 men between the ages of 18 and 40 for 37 types of HPV. Testing was performed on swabbed samples from the penis, as well as areas not protected by condoms (the scrotum, perineum and anus).

All of the men were surveyed about their sexual history, including how often they had used condoms in the past three months. Overall, 90 men said they “always” used condoms, while 154 said they never did; the rest reported inconsistent condom use.

As a group, the study found, men who always used condoms were less likely to test positive for HPV; 38 percent had HPV at at least one of the body sites tested, versus 54 percent of men who said they never used condoms.

Consistent condom users were also less likely to have cancer-related HPV strains: just under 17 percent tested positive for a cancer-related viral strain, compared with 36 percent of men who never used condoms.

When the researchers took a closer look at the data, they found that condoms appeared protective among men who’d had more than one partner in the past three months, but not those who said they’d been monogamous.

Among men who reported more than one partner, consistent condom users were 78 percent less likely to test positive for HPV than those who never or only sporadically used condoms.

Still, if men who said they always used condoms were accurate, that means that a “substantial” proportion of consistent users nonetheless acquired HPV, Nielson and her colleagues point out.

So while condoms may lower men’s risk of infection, they do not eliminate it. Part of that is likely due to transmission to areas not protected by condoms; Nielson’s team found smaller differences in HPV-positive rates among condom users and non-users when they specifically tested body sites not covered by condoms.

Other ways of lowering HPV risk include staying in a mutually monogamous relationship and being vaccinated against the virus.

Vaccines that protect against certain cancer-related strains of HPV are available for children and adults between the ages of 9 and 26.

SOURCE: Journal of Infectious Diseases, August 1, 2010.