The fact that gay men who practice unprotected anal intercourse (UAI) are largely versatile in their anal sex roles likely fuels HIV's rapid spread among the population, aidsmap reports. Versatile men also report vastly more frequent UAI than exclusive tops or bottoms.

Reporting their findings in the Journal of Acquired Immune Deficiency Syndromes, investigators from the EXPLORE study analyzed data from more than 2,500 HIV-negative gay men who reported having UAI. Recruited for the study between 1999 and 2001, the participants received an average of 3.25 years of follow-up. The study polled the participants quarterly, asking them about the role they had played during UAI: exclusively insertive (top), exclusively receptive (bottom) or both (versatile).

A total of 63 percent reported being versatile, and the participants in this group reported a median of eight incidents of UAI during the previous six months. Seventeen percent of the group were exclusive tops, reporting a median of just one UAI in the previous six months. Ten percent were exclusive bottoms, who also reported only one UAI in the previous six months.

When they did not know their partner's HIV status, the men were 51 percent more likely to report being the top. And when they knew their partner was HIV positive they were 2.34 times more likely to top.

Possibly helping to explain the high rates of HIV transmission among younger gay men, the study found that those 25 and younger were the most likely to report being an exclusive bottom. As the men got older, the odds of this fell so that the lowest rates were among those 36 and older. The study had a mean age of 34.

To read the aidsmap story, click here.

To read the study abstract, click here.