Men with prostate cancer who were previously infected with the sexually transmitted germ Trichomonas vaginalis are more likely to have an aggressive form of the cancer , compared with men who never had the STD , a new study says . Researchers say trichomonas , an STD , is most common in men ages 25 to 39 . The germ , a type of parasite , can infect the prostate and may cause inflammation that spurs the growth of prostate cancer later in life , says senior author Lorelei Mucci , Ph.D. , an assistant professor of epidemiology at the Harvard School of Public Health . `` Our underlying hypothesis is around inflammation and , in particular , we believe that inflammation from a variety of sources is leading to prostate cancer progression , '' she says . In the study , Mucci and colleagues compared 673 prostate cancer patients to 673 men without prostate cancer , and tested their blood for signs of a past infection with trichomonas . All the men were enrolled in the Physician 's Health Study , according to the report published this week in the Journal of the National Cancer Institute . They found that roughly one in five men had been infected with trichomonas at some point in his life . Men infected with trichomonas were no more likely to develop prostate cancer in general . But those with a past trichomonas infection were two to three times more likely to develop an aggressive and potentially life-threatening form of prostate cancer . Trichomonas affects 174 million people around the world each year , and , at any given time , about 3 percent of younger men are infected with trichomonas ; it is most common in men ages 25 to 39 . However , trichomonas is an STD that 's probably on more women 's radars than men 's because women are more likely to get symptoms such as discharge and itching . Health.com : How to protect yourself from HPV . Only one out of four men with trichomonas develops symptoms , and , with time , the infection often goes away on its own . ( The STD can be cured quickly with antibiotics . ) `` I think the only time men really seek any medical intervention is if their partner has been diagnosed and then they may go and get treated as well , '' says Mucci . `` I think the general feeling has been that this is an acute infection , it will eventually clear itself , and it does n't seem to be doing any real harm ; but in this case it may actually be doing harm -- you 're just not seeing the harm until 20 years in the future . '' Infections are just one factor that researchers are examining as potential players in the growth of prostate cancer , and others -- such as dietary choices -- are thought to influence prostate cancer risk as well . Health.com : 10 questions to ask a new partner . `` We are pretty confident that diet has an impact , '' says Dr. Peter C. Albertsen , of the University of Connecticut Health Center , in Farmington . Prostate cancer is rare in Asian countries but relatively common in Western nations , and researchers feel it 's probably due to some component of the Western diet , says Albertsen , who wrote an editorial accompanying the study . `` What this study explores and similar studies are exploring is whether there are potentially infectious causes that result in prostate cancer going from a relatively dormant disease to one that 's clinically significant , '' says Albertsen . `` This study raises the issue that a common bug , Trichomonas vaginalis , could be such an agent . '' While the link to prostate cancer may sound surprising , there are other cancers caused by STDs . For example , cervical cancer in women is caused by the sexually transmitted human papillomavirus ( HPV ) . ( However , HPV is a common infection and many women who are infected with the virus never develop cancer , which is relatively rare . ) Health.com : How HPV causes cervical cancer and abnormal pap smears . `` [ Although ] there is some evidence that suggests that the number of partners that a man has had over his lifetime is associated with increased risk of developing prostate cancer , '' says Mucci , the relationship is not as clear-cut for prostate cancer as it is for cervical cancer . There is no strong indicator that an STD causes prostate cancer , and researchers suspect that trichomonas is just one inflammation-causing factor that may contribute to the cancer or make it grow faster . `` We think that inflammation is what 's important , '' she says . `` This inflammation may result from trichomonas , a dietary factor , or it could result from oxidative stress from something like smoking or other factors . '' Health.com : Dating dilemmas -- 8 tips for telling your partner a health secret . Either way , it 's too soon to make any changes in the testing or treatment of either prostate cancer or trichomonas , both experts say . `` What needs to happen is a few more researchers need to tackle this issue to either nail this down as a true relationship or dispense with it , '' says Albertsen . Health.com : Who 's most at risk for STDs ? However , it 's an important issue to consider , he says . `` Right now if you asked if the average urologist or internist , 'Does Trichomonas vaginalis lead to prostate cancer ? ' , the answer would be no , and in fact this study does n't prove a cause-and-effect relationship , '' he says . `` But if we begin to see that infections in general can be associated with prostate cancer , we might begin to take a new view on this disease and the appropriate treatment leading up to it . '' Enter to win a monthly Room Makeover Giveaway from MyHomeIdeas.com . Copyright Health Magazine 2009 .
Study : Men with trichomonas vaginalis more likely to have aggressive prostate cancer . The germ is a type of parasite that can infect the prostate . It's not clear why it causes such an inflammatory response, but there are several theories about how it might be involved in this disease.