Many HIV-positive men sometimes have unprotected sex with women who are either HIV-negative or whose HIV status is unknown to them, according to a study conducted in New York City.

The findings also show that risky sexual behavior by HIV-positive men who have sex with women is variable, the researchers say, and “underline the importance of conducting risk screening ... on an ongoing basis, not just at entry into care.”

The heterosexual spread of HIV has become an “increasingly significant” element of the AIDS epidemic in the US, Dr. Angela A. Aidala and colleagues note in the Journal of Urban Health. Most research on preventing heterosexual HIV transmission has targeted women, the researchers add.

To better understand men’s role, Aidala and her team at Columbia University in New York City followed 278 HIV-positive men who were sexually active with women between 1994 and 2002, interviewing them every 6 to 12 months.

Thirty-seven percent reported having unprotected sex with a woman whose HIV status was unknown or negative at least once during the eight-year study period. The men’s sexual behavior varied significantly during the course of the study, with some men abstaining from sex for months at a time and others having sex with multiple partners, in some cases other men, throughout the course of the study.

Study participants’ sexual risk-taking was also variable, with periods of unsafe sex alternating with periods of safer sex, the researchers found.

Factors tied to unsafe sex included exchanging sex for drugs or money, problem drinking, being homeless, and active drug use. Men who had had sex with other men during their lifetimes were more likely to engage in unsafe sex during the course of the study, as were men who had a spouse or partner.

Older men and those who were taking antiretroviral drugs were less likely to have unsafe sex.

Overall, 19% of the men reported ever having sex with another man. White men were much more likely to have had sex with another man, with 36% reporting having done so at least once in their lifetimes, compared to 15% of black men and 20% of Latinos.

“A number of predictors of unsafe sex among African American men were not significant among the Latino sub-population,” the researcher found, suggesting that there may be ethnic differences in heterosexual HIV transmission.

They conclude: “Given the fluidity of the factors that have been shown to be significant predictors of unsafe sex among HIV-positive men sexually active with women, regular and repeated risk screening is essential.”

SOURCE: Journal of Urban Health: Bulletin of the New York Academy of Medicine, July/August 2006.