The composition and context of our neighbourhoods – and how we move through them – has been associated with HIV-related outcomes among racially minoritized groups (Duncan et al., 2021). As residents of one of the most racially segregated cities in the United States (Menendian et al., 2021), Black people in Chicago face a myriad of poor HIV outcomes due to their spatial segregation and marginalization (Gant et al., 2023; Oluyomi et al., 2023; Rimmler et al., 2022). Chicagoan Black sexually minoritized men (BSMM), in particular, experience disproportionately higher rates of HIV incidence compared to other sexually minoritized men (SMM) (Mustanski et al., 2019) and comprise over one-quarter of new diagnoses in the city (Getting to Zero Illinois Dashboard, 2022). However, few studies explore the links between spatial (im)mobility and HIV transmission risk behaviours exclusively among BSMM.

Geographic mobility – where, how far, and for how long someone travels over a given period – can impact several health outcomes (Morris et al., 2018), including one’s sexual behaviours that can cause HIV transmission (Kim et al., 2020). For example, mobility may be associated with condomless anal sex (Patel et al., 2014), transactional sex (Oldenburg et al., 2015), group sex (Lew et al., 2023), and using alcohol or drugs during sex (Tomkins et al., 2019). This is because individuals may experience less social control from known friends, family, or neighbours when they are away from home (DeLamater, 1981; Zenilman et al., 1999). “Journey-to” theory, which spans multiple disciplines, captures how mobility lessens the social controls that govern individual behaviours. In criminology, the “journey to crime” (committing a crime away from one’s residential neighbourhood) is associated with victimization and law enforcement outcomes (Donnelly et al., 2021; Luo et al., 2021). This theory has been applied to substance use research in which the “journey to overdose” (overdosing in a neighbourhood that is not one’s own neighbourhood) was found to result in more accidental deaths than if individuals overdosed at home (Forati et al., 2023). To extend this theory further, “journey to sexual behaviour” – having sex in neighbourhoods away from home – may be associated with greater rates of sexual behaviours that increase the risk of HIV transmission (Cassels et al., 2020; Dharma et al., 2023). Of course, mobility could also introduce individuals to neighbourhoods and networks with varying social norms that can also influence sexual behaviours (Frye et al., 2017). For this reason, it is important to unpack which aspects of BSMM’s geographic mobility (e.g., time spent away from home, having sex away from home) relate to which sexual behaviours that may increase HIV transmission risk.

While recent studies among SMM suggest links between mobility and sexual behaviours, none have exclusively studied these associations among BSMM. Duncan and colleagues found that SMM in New York City engage in “spatial polygamy” (using a survey measure) in which individuals spend time outside of their residential neighbourhood for a multitude of reasons like having sex and socializing – and these types of activity spaces differ by key characteristics that relate to HIV vulnerability (Duncan et al., 2014). In New York City among a racially and ethnically diverse sample of SMM, Kim et al. found that the size of one’s activity space, using a Global Positioning System (GPS) measure, was positively associated with having condomless anal sex (Kim et al., 2020). Geographic mobility – whether for sex, socializing, or other reasons – among BSMM in the United States remains poorly understood.

Current mobility and health studies, including those with SMM, use either survey or GPS-based measures, each with its own advantages and disadvantages. Survey measures, like from travel histories, are often favoured for describing the motivations for travel, but may be subjective and prone to recall bias (Rezaei et al., 2023; Zare & Pearce, 2022). GPS methods facilitate more objective measurement of mobility and allow for many different quantifications of the scale of movement – like size of one’s activity space or the proportion of one’s time spent away from home (Duncan et al., 2020). However, without contextualizing GPS-based measures with survey data, associations between mobility and health outcomes may suffer from “selective daily mobility bias” (Chaix et al., 2012). Furthermore, when used in isolation, either of these methods may produce a unidimensional picture of mobility that provides little information. For example, in Kim and colleagues’ GPS-based study (Kim et al., 2020), it is unclear whether the sexual acts associated with mobility occurred away from individuals’ home neighbourhood (as mobility and sexual behaviours were measured separately) – making it difficult to test the specific effects of traveling for sex. In a sample of young BSMM and transgender women in Chicago, Kolak and colleagues found through survey data that individuals with sexual partners who lived in different non-neighbouring community areas were more likely to have exchanged sex for money, shelter, and other goods (Kolak et al., 2021). This study aims to combine survey and GPS methods to comprehensively describe different mobility dimensions and explore their associations with sexual behaviours, enhancing the understanding of contextual determinants of HIV risk.

Applying “journey to” theory (Forati et al., 2023; Luo et al., 2021), i.e., journey to sexual behaviour, this study aims to examine multiple dimensions of geographic mobility using GPS and survey measures and their associations with sexual behaviours that may increase HIV transmission risk in a well-characterized sample of Chicagoan BSMM. We leverage individual-level GPS data uniquely linked with survey data from the Neighbourhood and Networks (N2) Cohort Study in Chicago to measure mobility more granularly – including across sex and socializing areas – to deepen understanding about the associations between mobility and sexual behaviour. As place matters for Chicagoan BSMM’s uptake of HIV services (Behler et al., 2018), a deeper characterization of their spatial mobility and associated HIV-related risks can help programs to meet these men where they are.

Beyond the nuanced examination of multidimensional geographic mobility, this study uniquely examined journey to sexual behaviour theory and generated evidence for BSMM – for whom there is little data despite their disproportionately high HIV outcomes and the structural racism they experience in American cities and around the world. This study used both survey and GPS-based measures to characterize the temporal, spatial, and social dimensions of BSMM’s mobility. These comprehensive measures may improve our understanding of the relationship between mobility and HIV-related sexual behaviours. BSMM in our Chicago sample were highly mobile, and having sex or socializing in a neighbourhood other than their residential neighbourhood was associated with elevated risk of having condomless anal sex with a casual partner.

In this study, BSMM largely under age 30, with low-income and limited educational attainment, were highly mobile (e.g., they spent on average half of their time away from their home neighbourhood). By comparison, young SMM in the New York City P18 study spent on average one third of their time away from their home neighbourhood (Duncan et al., 2020) – suggesting that it is not age that explains these differences. Possibly, the experience of structural racism drives mobility. In racially segregated Chicago, young Black men may navigate different neighbourhoods to counteract the negative effects of segregation, seeking opportunities like work, education, and healthcare (Asabor et al., 2022; Council et al., 1990; Hedman et al., 2021). Moreover, young BSMM may travel to access LGBTQ+ friendly health and social services, potentially better resourced in communities beyond their own . Racial segregation, combined with inadequate social support for SMM living in racialized communities, could drive the high mobility rates we see in this sample, but more research is needed to understand the different mobility experiences between those living in Black vs. non-Black neighbourhoods.

The association between traveling for sex and a potentially higher HIV transmission risk found in the current study reflect similar mechanisms found in the “journey to crime” and “journey to overdose” literature. Associating mobility with sexual behaviours, having sex away from home correlated with condomless anal sex with any partner and casual partners. This was similar to New York City study that found that SMM were more likely to have condomless oral sex if they had sex away from their residential neighbourhood than if they had sex close by (Duncan et al., 2014). Our study may provide evidence for the role of social controls in “journey-to” theory, as people may be more likely to engage in certain behaviours when away from home (Frye et al., 2017).

The proportion of one’s activity space and time spent outside the home buffer area was not associated with specific sexual behaviours. This differs from that of another SMM-focused study in New York City, which found that the risk of condomless anal sex increased for each additional square kilometre of activity space (Kim et al., 2020). A qualitative study among Black and Latinx SMM in Los Angeles, CA, is also contradictory: men who felt less belonging were more likely to spend time away from home (Cassels et al., 2020), and likely to experience less social cohesion which would impact sexual risk (Saleh et al., 2016). One explanation for these null findings is that the size of activity spaces among this sample of Chicagoan BSMM may be too similar to detect any differences by an outcome of interest. In this study, the SD equalled the mean of activity space sizes, leaving very little variability.

The study had limitations. First, 87 (24%) of participants were excluded because they did not contribute GPS data. However, a sub-analysis revealed this group did not differ by sociodemographic characteristics or sexual behaviours (Table 1). Second, condomless sex may be an inadequate marker of HIV transmission risk (Jin et al., 2015). Especially in regular partnerships, it is unclear whether both partners adopt other HIV prevention measures, like monogamy, joint testing, or PrEP. Third, due to selective daily mobility bias, we could not disentangle whether mobility caused the sexual behaviour or vice-versa. This is because people may travel away from home with the intention of engaging in certain sexual behaviours away from their normal social controls. Fourth, unmeasured confounding may have created a spurious association between mobility and condomless anal sex. For example, experiencing discrimination against one’s sexual orientation or HIV positive status could drive them both to spend time away from their home neighbourhood and to engage in less safe sexual practices (Babel et al., 2021; Newcomb & Mustanski, 2011). However, since associations were relatively weak between mobility and other sexual behaviours, we think the confounding effects of such unmeasured variables are minimal. It is also possible that discrimination is a mediator if BSMM experience stigma or harassment only outside of their home neighbourhood. This may be true if they visit predominantly white neighbourhoods with historical LGBTQ presence, as some non-white transgender and nonbinary people reported in a qualitative study in New York City (Lampe et al., 2020).

Importantly, mobility measures might be inaccurate if participants’ mailing addresses do not represent their true home locations. This is one explanation for the large number of participants who spent no time in their derived home neighbourhoods. Furthermore, participants’ “home” location may frequently change over the study period – so their mailing address may not be the same home location they would have reported while wearing the GPS device. For example, young people may move residences with more frequency, including for reasons like entering cohabitating partnerships. Also, over one-third of the sample reported unstable housing in the past six months – presenting a challenge in ascertaining home locations beyond our specific study in the context of the housing crisis (2023 Snapshot of Homelessness in Chicago, n.d.).

This study contributes in various ways to the literature on mobility and HIV. First, we built a novel and reproducible analytic framework to examine multiple dimensions of mobility (spatial, temporal, and motivation-specific). Second, we leveraged survey-based mobility measures to supply a deeper understanding of more objective measures obtained from GPS devices. Third, by examining multiple sexual behaviours vis-à-vis multiple mobility indicators, this paper serves to develop hypotheses about specific mechanisms that might link mobility and HIV risk. For example, travel for socializing may only cause condomless sex with casual partners as opposed to regular partners-necessitating a different set of safe sex interventions. Finally, by focusing on a sample of racially and sexually minoritized men, we achieved an adequate sample size – rare in other HIV research (Maulsby et al., 2014) – to describe the varied risks and vulnerabilities within this key population group.

This study highlights various directions for future research. First, beyond the need for more research with BSMM, specific underrepresented populations warrant centring in mobility and HIV research. Studies could over-sample transgender populations, for whom there is a dearth of data (Goedel et al., 2019). Future research could also generate evidence in rural and suburban communities to advance our understanding beyond urban BSMM. Our findings are likely not generalizable to BSMM living in areas without public transportation networks, where their mobility depends on car access and traveling further distances. Second, mixed-methods studies might disentangle the issue of reverse-causation, i.e., whether individuals travel to engage in certain behaviours, or their travel leads them to engage in those behaviours. Such a deep dive into the mechanisms that connect mobility and sexual risk could better inform behaviour change interventions. Third, mobility measurement everywhere would benefit from more accurate definitions of “home.” Here – as in other studies – we equate “home” with a residential address (Duncan et al., 2020), but home can mean many things to different people at different times. Finally, future research could relate multidimensional mobility to HIV service uptake and retention, like PrEP and ART (Chen et al., 2019; Kim et al., 2021).

Due to their reduced condom use, BSMM who have sex away from home – even if just in a different Chicago community area – are at higher risk for HIV acquisition or for transmitting the virus. This means that interventions focused on behaviour change like increasing condom use and other healthy sexual practices should not just be spatially targeted to the areas where high numbers of people vulnerable to HIV reside, but also to where they have sex. This may come in the form of place-based interventions, like promoting safe sex at gay bars and other social venues. With GPS-based mHealth technology, behaviour change interventions could also use geofencing to deliver messages to consenting users when they enter areas where they are more likely to report sexual activity (Tobin et al., 2023). Messages may direct app users to where they might be able to access condoms or PrEP or guide them on how to negotiate safer sex. By considering individuals’ activity spaces vis-à-vis their sexual behaviours, more contextually-relevant place-based interventions may be able to interrupt HIV transmission and lessen the HIV burden among BSMM (Duncan et al., 2019).

In a racially and sexually minoritized population, this study among BSMM demonstrated the richness that can be achieved in mobility and HIV research by examining multiple dimensions of human movement. While the scale of BSMM’s daily travel away from home was not associated with sexual behaviours that increase HIV risk, having sex or socializing in neighbourhoods away from home may lead to increased risks through decreased condom use during anal sex. Due to the lower social control in places distant from home, some people may either engage in sexual risk behaviour when they are there or purposely travel there to engage in this behaviour. To curb the epidemic among BSMM, more research is needed to understand BSMM’s mobility patterns – including where they spend their time and why – so that future interventions can be designed with them in mind, meeting them where they are.