While Black gay and bisexual men comprise a segment of the United States population more likely to be infected with HIV than any other, the group has not been found to engage in more HIV risk behaviors, researchers say, prompting a closer look at why the disparity persists.

According to a recent study published in the Journal of Acquired Immune Deficiency Syndromes, three factors may be driving the HIV rates among Black gay men: age gaps between partners, sexual networks more tightly drawn by race, and the fact that partner familiarity affects condom usage.

For the study, investigators recruited 143 HIV-negative men who have sex with men (MSM) under the age of 40 of diverse ethnicities from across the U.S. Participants were asked to keep a weekly diary of their sexual encounters over a three-month period, updating the diaries every week. The group was also asked to score their partners’ age difference from them, their gender, familiarity and their perceived HIV status.

What they found: that while Black men were considerably less likely to report having unprotected sex than other racial groups, they were the most likely to have sex with other Black men (African Americans were 11 times more likely to have black partners than partners of another race) and more likely to have partners who are older than they are, another group shown to have higher rates of HIV as compared with younger men.