Men who have sex with men (MSM) are disproportionately affected by HIV across Canada, provincially in British Columbia (BC) and locally in Vancouver.
In BC, MSM make up about half of new HIV infections as well about half of those living with HIV. Provincially, the HIV epidemic among MSM is concentrated in Metro Vancouver, where the majority of new infections are diagnosed. While the overall number of new HIV infections in BC is declining, the number of new diagnoses among MSM remains stable. Reliable population size estimates can help understand this dynamic, informing public health and policy decision-making.
Estimating the size of the MSM population is made challenging by a number of factors, including: inconsistent sexual orientation measurement, lack of collection of sexual orientation in census data or routine health surveillance, social stigma affecting research participation, small sample size, and the fact that gay, bisexual and other MSM comprise a ‘hidden’ or hard to reach population.
Developing reliable estimates for the size of key populations, such as MSM, improves health services planning and implementation and informs a better understanding of the HIV epidemic.
We estimated the size of the Metro Vancouver MSM population using diverse data sources and methods. Data sources included:
- a nationally representative population health survey (Canadian Community Health Survey),
- a cross-sectional bio-behavioural MSM HIV study (Momentum Health Study),
- HIV testing services data from BC Centre for Disease Control STI clinics (Health Initiative for Men (Davie Clinic), Bute St. Clinic, Provincial Clinic), and
We included data sources measuring sexual orientation via the three major dimensions of sexual orientation (i.e. sexual identity, behaviour, attraction). Estimation methods included direct estimates, “Wisdom of the Crowds” (WOTC), and a multiplier method.
Population estimation results ranged from 10,000 to 41,800, with a median of 27,200.
This median represents 2.9% of the adult male population in Metro Vancouver, consistent with MSM estimates in the United States. Previous studies have shown that as many as 10-40% of gay, bisexual and other MSM may be unwilling to disclose sexual identity or same-sex sexual behaviour as a result of social stigma and structural discrimination. As such, when this sensitivity was applied, our results ranged from 3.2%-6.2% of the Metro Vancouver adult male population.
This study leveraged several local data sources and multiple methods to produce a robust estimate of the size of the MSM population in Metro Vancouver. Findings support better understanding of the HIV burden among MSM in Metro Vancouver and corresponding public health decision-making and health services planning for this HIV priority population.
For more information
Contact the researcher and lead author, Ashleigh Rich
- Rich AJ, Lachowsky NJ, Sereda P, Cui Z, Wong J, Wong S, Jollimore J, Raymond HF, Salway Hottes T, Roth EA, Hogg RS, Moore DM. Estimating the size of the MSM population in Metro Vancouver, using multiple methods and diverse data sources. Journal of Urban Health; 2017 Jun 19 [Epub ahead of print]. Available at: https://www.ncbi.nlm.nih.gov/pubmed/28631060