Doctors continue to study the relationship between vasectomies and prostate cancer risk. And men, it should come as no surprise, continue to pay close attention.

There had been a time when men who had vasectomies were informed as a matter of course that they were placing themselves at a higher risk for prostate cancer. More recent studies, happily, provided data that downplayed any connection.

The latest study, out of Harvard Medical School, supports the no-connection thesis – but with one caveat. The research shows a small increase in the risk for low-intermediate–grade prostate cancer in men who had a vasectomy. The findings are not, however, outside the margin of error due to differences in health-monitoring behaviors.

"However, a large risk can be ruled out with confidence," said Meir Stampfer, MD, DrPH, professor of medicine, Harvard Medical School. "Since the absolute increase in risk, if any, is modest at most, I believe this should not be a factor is deciding about vasectomy.”

Stampfer's study included 84,753 men aged 35 to 79 years, with 15 percent reporting that they had undergone a vasectomy. The data did not support a significant association between vasectomy and prostate cancer risk, and the results remained unaltered after adjustment forbody mass index, smoking status, marital status, level of education, alcohol consumption, physical activity, and protein from dairy sources.

No meaningful connection between vasectomies and prostate cancer-related mortality was found. There was, however, an association with age. Compared with men who had not had undergone a vasectomy, those who did so when they were younger than the median age were at a significantly increased risk for prostate cancer. Conversely, the researchers observed no meaningful association among men who were older than the median age when they had their vasectomy.

The Harvard researchers make a point of underscoring that detection bias in some of the previous studies linking vasectomies and prostate cancer could obscure "a true association with advanced or fatal disease if tumors among men with vasectomy tend to be detected and treated earlier compared with men without vasectomy."

The research was published in the Journal of Clinical Oncology.