Study tracks risk and protective behaviors related to transmission of HIV/AIDS in young adults

A number of behaviors in younger adults that increase risk for the transmission of HIV/AIDS have declined or changed between 2010 and 2020, according to the national Monitoring the Future study.

In the ongoing national study of high school graduates 21-30 years old, investigators at the University of Michigan have been tracking risk and protective behaviors related to the transmission of HIV/AIDS. Each year since 2004, high school graduates have been surveyed as part of the Monitoring the Future study.

While substance use is the primary focus of the study, it also looks at risk and protective behaviors related to the spread of HIV among young adults as they pass through their 20s—an age band that accounts for a disproportionate number of new HIV infections, according to the Centers for Disease Control and Prevention.

An important risk behavior for the transmission of HIV is having more than one sexual partner. Between 2010 and 2018, the proportion of young adult females showed little change in having multiple sex partners (from 21.1% to 21.9%). However, males reporting two or more partners fell from 28.3% to 21.7% over the same time frame.

That decline among males has largely closed the gender gap in having two or more sex partners. There does remain a gender gap in having a larger number of sexual partners. In the 2020 survey 11.5% of young adult males reported having four or more sexual partners in the prior 12 months vs. 7.5% of females.

Those having no sexual partners in the prior 12 months have the least risk for the transmission of HIV—and the investigators have found that such abstinence has been growing. Among 21-to-30-year-old males, abstinence rose significantly between 2008 and 2020, from 14.4% to 23.5%—an increase of nearly two-thirds. Among females of the same age, abstinence also rose, though by less, rising from 12.8% in 2008 to 16.5% in 2020—an increase of just over a quarter.

Young adult males now have a considerably higher rate of abstinence than young adult females due to their greater absolute increase up until 2018. Since 2018, the rate of abstinence has leveled for both genders.

Needle sharing by those using illicit drugs is another risk factor for the transmission of HIV/AIDS. The prevalence of needle sharing in the prior 12 months has changed relatively little since 2004, when questions about it were first asked on MTF surveys of young adults.

The lifetime prevalence of needle sharing in this population of high school graduates has remained below 1% and the percentage reporting this behavior in the prior 12 months has remained below 0.3%. Lifetime prevalence has been higher among males since 2010 and the gender difference has increased since 2016; but there has not been a consistent gender difference in their annual rate of needle sharing.

The use of condoms is considered a protective behavior and has been in a gradual decline among both young adult males and females since roughly 2013. In 2020, only 31.9% of sexually active males said they used condoms “most times” or “always”—as did 22.6% of females.

Getting an HIV test in the prior 12 months—another protective behavior—has been substantially lower for males than females, and the gap between them has grown considerably over the life of the study. The proportion of males getting tested for HIV in the prior 12 months has remained fairly stable at around 14%-16%, while the proportion of females getting tested has risen some from 22.9% in 2006 to 27.2% in 2020—a positive development.

A particularly high-risk group for HIV/AIDS is men who have sex with other men, including those who have sex with both genders. The study found that the percentage reporting having sex exclusively with male partners during the prior 12 months has more than doubled from 3.9% in 2005 to 8.3% in 2020. Men reporting having both male and female sex partners also has more than doubled from 1% in 2005 to 2.3% in 2020.

Same sex behavior among women is not nearly as important a vector for the spread of HIV, but it also shows similar increases, with nearly a doubling between 2009 and 2020 in the percentage reporting exclusively female sex partners (from 2.3% to 3.8%) and in the percentage reporting both male and female partners (from 1.9% to 3.8%). Most of these increases for both males and females have occurred since 2011. The investigators note that some of these increases may be due to recent historical changes in the social acceptability of admitting to homosexual behavior.

Males in this high-risk group having male sex partners are much more likely to report having been tested for HIV/AIDS in the prior 12 months (42.1%) than males who had only female sex partners (16.8%).

So, there is some compensatory protective behavior in this very high-risk group in the form of testing. But, while they have much more testing, they do not show any greater frequency of another protective behavior—using condoms. In 2020, about the same percentage of young men ages 21 to 30 who had sex exclusively with men report using condoms ‘most times’ or ‘always’ (36.7%) as males who reported having only female sexual partners (36.4%).”

Lloyd Johnston, lead author on the current HIV/AIDS monograph from MTF and research professor at the U-M Institute for Social Research

Johnston said the data only go through spring 2020, so the survey did not capture most of whatever effects the COVID-19 pandemic may have had.

“We hope to be able to report on any changes in the situation in 2021, still during the pandemic, and again in subsequent years,” he said.

The Monitoring the Future study began in 1975 and every year since has collected follow-up data on high school graduates first surveyed in their senior year of high school. Through 2017, those graduates ages 19 through 30 have been surveyed by mail—then in 2018 and 2019, half were surveyed by mail and half online.

In 2020, all follow-up surveys were done online, and there appears to be little to no effect of that changeover on the results of the HIV questions. Respondents ages 21 through 30 were asked a set of questions about their known risk behaviors and known protective behaviors related to the transmission of HIV/AIDS. The total number of individuals participating in this part of the study was 11,800; but there actually were 33,800 observations, since participants could be included on multiple occasions as they grew older.

Co-authors on the monograph include U-M professors John Schulenberg, Patrick O’Malley, Megan Patrick, Richard Miech and Jerald Bachman.