This systematic review identified consistent evidence of a high burden of violence against sex workers globally.
Despite a substantial human rights and public health concern, there are major gaps in documentation of violence against sex workers in most parts of the world, with the majority of studies from Asia, and only 2 studies from Central Africa. The review reveals a growing body of research demonstrating a link between social, physical, policy, and economic factors, alongside more proximal interpersonal and individual factors (e.g., sexual and drug risk practices, psychosocial factors), and elevated rates of violence against sex workers. Results indicate the need for more methodological innovation (e.g., longitudinal studies, mixed methods, multilevel analyses) in research and intervention design and evaluation, as well as increased measurement rigor, to better document and respond to violence against sex workers.
Key Correlates of Violence Against Sex Workers
Policing practices as enforcement of laws, either lawful (e.g., arrest) or unlawful (e.g., coercion, bribes, violence) are a critical means for measuring how criminalization and regulation of sex work may have a negative impact on risks of violence against sex workers. In our review, there was consistent evidence of an independent link between policing practices (e.g., arrest, violence, coercion) and elevated rates of physical or sexual violence against sex workers.46,48,55,60 These data support growing evidence-based calls, including World Health Organization and United Nations guidelines and Global Commission on HIV and Law,8–10 of the critical public health and human rights need to remove criminalized laws targeting sex work (e.g., decriminalization) as a barrier to basic health, safety, and rights to protection of among sex workers.
In addition to legislative changes at national or district levels, structural policy changes through police–sex worker engagement have also been proposed.8–10 Our review found 1 study showing the success of a combined structural and community-led intervention in a district in southern India (including engagement with police stakeholders, sensitivity training of police, and community empowerment) and associations with reduced violence experienced by sex workers over the year. Although challenges with replication of structural and community-led interventions are well-known,79 qualitative literature suggests that sex work engagement with police may have had success in other settings in changing the environment within which sex work operates and promoting increased capacity for sex workers to safely engage in sex work and report violence to authorities.80
In our review, we also found evidence of the role of the work environment in shaping risks for violence among sex workers, with data from 3 countries showing sex workers in street or public-place environments to be at highest risk of violence. Laws that criminalize or regulate sex-work environments (e.g., prohibitions on operating bawdy houses) shape access to indoor work environments for sex workers in many settings globally.1 Although there is growing literature of the role of supportive indoor sex-work environments (e.g., supportive venue-based policies and practices, enhanced physical access to health services) in promoting condom use,80–82 our review found no studies examining the more complex and nuanced nature of work environments in promoting or reducing rates of violence among sex workers. In light of important qualitative work from a number of settings,37,80,83 there is a clear need for epidemiology to better document these structural interventions as they unfold.
Alongside known proximal risks for violence (e.g., drug use, sexual risks with intimate, nonpaying partners), our review also documented a number of more upstream factors as linked to risks of violence against sex workers, including gender and economic inequities, voluntary migration and population movement, and history of trafficking or forced labor, further supporting need for violence prevention at structural and community levels. Of note, although drug use was measured as an individual behavior among sex workers in a number of studies, no studies examined drug use of the perpetrators and few studies considered the interpersonal or partner-level nature of drug use within sex-work environments.
As epidemiology continues to better measure and document both upstream and downstream factors, there is increasing need for multicomponent structural and community-led interventions to address and respond to violence against sex workers. Only 2 studies that examined interventions were documented in this review, suggesting a major scientific gap in evaluating interventions to reduce violence against sex workers.37,41 Because many programs and interventions happen organically (e.g., sex work–led interventions) or outside the control of science (e.g., policing policy changes), there is a critical need for more methodological innovation in evaluating interventions, in partnership with sex-work communities, including engagement with a range of stakeholders (e.g., police, clients, managers, government). Furthermore, because of the highly context-specific nature within which social, physical, policy, economic, and interpersonal factors are embedded, better dialogue between epidemiology and social sciences is a priority.
Strengths and Limitations
The cross-sectional nature of almost all of the studies available, with most based on convenience samples, limits the strength of the evidence and highlights the need for research that is of higher methodological quality. Cross-sectional studies cannot assess temporality and, thus, causality in the relationship between an explanatory variable or risk factor (e.g., being arrested) and an outcome. Some of the risk factors in the studies assessed would better be viewed as outcomes, or as being in a complex synergistic relationship with the outcome. Longitudinal studies among sex workers are rare, but critically needed to shed light on drivers of violence against sex workers, as has been done in other populations.24 More work also needs to be done on understanding how to measure structural risk factors for violence that may operate differently on micro and macro levels. In this regard, there is a strong body of social science and qualitative literature as theoretical literature on structural interventions that can be used to help guide epidemiology.33,79 The majority of associations were simple risk factor–outcome associations, which fail to take into account the complex interrelationships between factors that produce violence (e.g., social stigmatization of sex work, criminalization of sex work).
We identified no studies on perpetrators of violence against sex workers in this review, with all studies focusing on samples of sex workers. This lack of perspective is a substantial limitation to understanding how violence against sex workers can be mitigated and to developing effective prevention that includes both men and women. Increasing calls are being made to include clients, intimate or nonpaying partners, and third parties (e.g., police, managers) of sex workers in research and programming with sex workers, particularly with respect to HIV and other STIs.84–86
Because we limited the search to English-language studies from North American databases, studies published elsewhere may not be included. As probability-based sampling frames of sex workers are difficult to create, it is likely that the studies we included have limited generalizability across settings. Our review only included peer-reviewed literature of epidemiological studies and excluded other potential sources of data, both peer-reviewed qualitative and social science literature and gray literature. Although such data can be useful, we chose to restrict our review to capture the highest quality peer-reviewed evidence to better inform responses to violence against sex workers. It is possible that we missed some studies that would otherwise have been eligible; this is a limitation faced by all systematic reviews. However, we attempted to address this limitation by having multiple reviewers (who each conducted independent reviews using the same method with which to search and extract data) and by contacting authors of publications to clarify if or how the study should be included and classified.
As our study’s aim was to review the correlates of violence, we did not search for or include studies that included only violence prevalence estimates without assessing correlates (i.e., we only included violence prevalence estimates that came from studies examining correlates of violence with bivariate or multivariable analysis). Thus, the violence prevalence estimates provided in this study cannot be considered a comprehensive collection and are an underestimate of the total violence prevalence estimates available in the literature. Nevertheless, results consistently showed a high prevalence of violence against sex workers in a range of settings.
Few studies examined violence by intimate or other nonpaying partners and thus we were unable to make conclusions related to prevalence or correlates of intimate or other nonpaying partner violence compared with workplace violence. We were limited from making comparisons between female sex workers and transgender or male sex workers, because of the few studies available (3 studies with a sample population that included combined female and transgender; 1 study with a sample of men who have sex with men and transgenders). As gender or sexual identity has been identified as a key factor influencing pathways of violence against sex workers in qualitative studies,30 the lack of studies on transgender and male sex workers is a key gap in research that should be addressed in future studies. For each correlate, a limited number of studies was available to draw definitive conclusions. Moreover, we could not conduct a meta-analysis because of the range of measures of different risk factors and violence outcomes. A standardized approach to measuring and collecting data to document prevalence and correlates of violence against sex workers would help address these limitations.
This systematic review reveals a high burden of violence against sex workers globally, and documents existing evidence of the social, physical, policy, economic, and interpersonal correlates of violence against sex workers. The review supports increasing evidence-based calls to make violence against sex workers a public health and human rights priority on national and international policy agendas, and the urgent need for structural research and interventions to better document and respond to the contextual factors shaping violence against sex workers. These include structural changes to legal and policy environments (e.g., decriminalization, policing practices), work environments, gender and economic inequities, population movement, and stigma. In this regard, measurement and methodological innovation (e.g., longitudinal, multilevel, and mixed-methods research) and rigor, in partnership with sex-work communities, are critical.