The sexual behaviour and sexual health of heterosexual-identifying men who have sex with men:understanding an understudied population to inform public

According to surveillance data from Public Health England, men who have sex with men (MSM) remain at higher risk of HIV and other sexually transmitted infections (STIs) relative to other men, and accounted for a disproportionate number of STI diagnoses in England in 2016 including 49% of gonorrhoea diagnoses and 81% of syphilis diagnoses (1). Data from the third British National Survey of Sexual Attitudes and Lifestyles (Natsal-3), a large probability sample survey of the general population undertaken 2010-12, estimated that 2.6% of men aged 16 to 74 years old were MSM (defined as reporting one or more same-sex partner(s) in the 5 years prior to interview), and of these, an estimated 25-30% identified as heterosexual. Furthermore, Natsal-3 estimated that only 17% of heterosexual-identifying MSM had attended a sexual health clinic in the last 5 years, compared to 48% of gay MSM and 37% of bisexual MSM. This is despite the fact that fewer heterosexual-identifying MSM report usually using condoms when compared to gay MSM (33% vs 62%). This might lead to heterosexual-identifying MSM and their partners (male or female) being at greater risk of undiagnosed STIs. Around 86% of the heterosexual-identifying MSM interviewed for Natsal-3 reported also having female sexual partners (compared to just 9% of gay MSM), and so this population might act as an important bridge between the gay and straight communities for HIV and other STIs. This might require public health intervention, given studies that have found that behaviourally-bisexual men (men who have sex with both men and women) are more likely to be HIV-positive or to have reported an STI diagnosis than men who have sex exclusively with women (2-4).

Although targeting sexual health campaigns towards men identifying as gay or bisexual might be justified as an effective way of reaching MSM, these campaigns may fail to reach heterosexual-identifying MSM. In the worst case, this may contribute to their exclusion from interventions because heterosexual-identifying MSM might not visit gay clubs, bars or websites where campaigns are often promoted, and may not identify with the language used. For example, Natsal-3 data also showed that around 80% of heterosexual-identifying MSM (and approximately 61% of bisexual MSM) reported never visiting gay pubs, compared to only 13% of gay-identifying MSM. Alternative methods of targeting this group, such as through social or sexual networks or via geospatial networking websites or apps, and by using messages focused on behaviour, may therefore be more successful than those based on identity (5). In order to implement well-designed public health interventions that will reach these men, heterosexual-identifying MSM need to be better understood, in terms of their sociodemographic and clinical characteristics, their sexual behaviour (including risk behaviour), characteristics of their partners and wider sexual networks, and their STI and other health risks.

This project aims to systematically synthesise data from Natsal-3 and other community-based convenience sample surveys in the UK and from other developed nations (at the time of writing, to include Sweden, New Zealand and Australia), and use these data to develop a better understanding of heterosexual-identifying MSM, in terms of their sociodemographic characteristics, sexual behaviour and health (physical, mental and sexual). Qualitative interviews will also explore in greater detail findings and questions that arise from quantitative work, and also probe how these men connect with public health interventions and campaigns targeted at MSM. These data will be used to inform the need for, design of, and implementation of public health interventions to improve the health of this group and that of their partners, sexual networks and the broader population.