February 1, 2011
A new long-term study of Amsterdam men who have sex with men (MSM) shows the need for targeted HIV prevention messages, say researchers.
Dr. Iralice A.V. Jansen, of the Public Health Service of Amsterdam, and colleagues followed 1,642 MSM for up to 25 years. The team found that from 1984 to 1988, the percentage of men who reported unprotected anal sex in the last six months declined from 78 percent to 33 percent. The rate slowly ticked up to 38 percent in 1995; by 2009, it had reached 55 percent.
When the researchers looked at yearly rates of new HIV infections, they found a significant drop during the study's earlier period, from 8.6 percent of MSM in 1985 to 1.3 percent in 1992. But beginning in 1996, a small increase was detected, reaching 2 percent in 2009.
According to the findings, the biggest HIV risk factor was unprotected sex with a casual partner. MSM who reported unprotected receptive sex with a casual partner in the six months prior were six times more likely to become HIV-positive during the study. "There is no doubt that prevention should continue to focus on their sexual behavior with casual partners," said the team.
In addition, MSM should be cautious with steady partners as well. One-quarter of all HIV infections during the study period were likely transmitted from a steady partner. A growing proportion of infections among men in their 40s and 50s was associated with steady partners; why is not clear, the team said. It could be that older men were more likely to be in long-term relationships and had fewer casual partners compared to younger MSM.
"Targeted prevention messages should continue to focus on sexual behavior with casual partners, but also on sexual behavior within steady relationships," the authors concluded.
The study, "Ongoing HIV-1 Transmission Among Men Who Have Sex With Men in Amsterdam: A 25-Year Prospective Cohort Study," was published in AIDS (2011;doi:10.1097/QAD.0b013e328342fbe9).