Men who have sex with men (MSM) is the term used to categorize males who engage in sexual activity with other males, regardless of how they identify themselves. The term was created in the 1990s by epidemiologists as a surveillance tool to better identify the route of HIV transmission and monitor disease spread through male-male sexual activity.
Prior to the use of the MSM designation, researchers used only identity-based analyses—and risk measures could be flawed. For example, men who identified as “gay” or “bisexual” weren’t necessarily sexually active, while those who identified as “straight” might be sexually active with other men.
MSM instead focuses on behavior rather than cultural or social self-identification, thereby providing a clearer picture of HIV infection rates. That, in turn, provides a better understanding of the implications of HIV prevention, including which prevention tools could be most effective in different populations.
Studies vary by community and culture, but research conducted by the New York City Department of Health and Mental Hygiene revealed that of the 4,200 men interviewed by telephone:
- Nearly one in ten who identified as straight had sex exclusively with other men.
- 70% of straight-identifying men who engaged in male-male sexual activity at one time or another also reported that they were married.
- 10% of married men who identified as straight had reported same-sex behavior during the course of the previous 12 months
HIV Statistics Among MSM in the U.S.
While MSM represents between 2 and 6.8% of the U.S. population, this group accounts for 55% of all HIV infections.
According to the Center for Disease Control and Prevention (CDC), if the current trend continues, as many as one in six MSM will be infected with HIV in the course of a lifetime. The prospects appear even grimmer for African American MSM, with current projections suggesting an astonishing 50% lifetime risk of acquiring HIV.
In their 2014 surveillance, the CDC further noted key disparities in HIV infections among MSM:
- MSM represented 67% of all new HIV diagnoses and 83% of new diagnoses among men aged 13 and over.
- Young MSM between the ages of 13 and 24 account for 92% of all new HIV infections among men.
- HIV rates among Hispanics/Latinos are of growing concern. While new HIV diagnoses among white and African American MSM have been relatively steady (down by 6% and 2%, respectively, since 2010), rates among Hispanic/Latino MSM have increased by 13%.
- Today, there is an estimated 687,000 HIV-positive MSM in the U.S. Of these, 15% remain undiagnosed.
- Among those diagnosed with HIV, only 57% remain linked to HIV-specific care for more than a year following diagnosis, while only 58% on HIV therapy were able to sustain undetectable viral loads indicative of treatment success.
These statistics align, to some degree, with HIV epidemics in other parts of the world. While the incidence of HIV (the number of infections occurring over a specific period) may be higher in some countries, the HIV prevalence (the portion of a population affected) is almost universally higher among MSM.
Epidemiological research has suggested that the HIV prevalence among MSM is between three and six times greater in the Middle East, Europe, East and Central Asia, and the Oceanic region, and anywhere from 15 to 25 times greater in sub-Saharan Africa, Central America, South America, and South and Southeast Asia.
How Epidemiological Research Informs HIV Prevention in MSM
The aim of epidemiological research is to provide an unbiased look at how the disease is transmitted and not who was “responsible” for transmission. As such, it provides ways to implement prevention strategies without judgment and (ideally) without political or moral influences.
One such example is the use of HIV pre-exposure prophylaxis (PrEP) in MSM. The strategy, in which the daily use of Truvada (tenofovir + emtricitabine) can reduce a person’s chance of getting HIV by 90% or more, has been studied extensively in MSM to see how its use could be most effective. As a result of the studies, PrEP is not recommended for all MSM, but rather for those who are at a high risk of infection.
Why? To be effective, PrEP requires daily dosing that many men are not able to maintain. As such, researchers fear that drug resistance may develop needlessly in MSM who may already have other means to protect themselves. This, along with the cost of treatment and possible side effects, has established PrEP as a vital tool for groups less likely to have other means of self-protection.
These include gay or bisexual MSM who may be stigmatized in their communities and fear the disclosure of their sexual orientation. It can also include younger MSM (since youth, in general, are less likely to use condoms) and illicit drug users who are inherently vulnerable to infection.
PrEP research into high-risk MSM has taken a more “real world” approach, assessing how gay and bisexual men behave rather than trying to change their behavior. With this approach, prevention tools like PrEP can be sustainable. This helps ensure that preventive efforts are placed squarely where they will have the greatest benefit.