A recent study that reveals the most accurate estimate of the number of Metro Vancouver men who have sex with men (MSM) is providing a better understanding of the scope of HIV among this at-risk population.
According to the study’s lead author Ashleigh Rich, a PhD student in UBC’s School of Population and Public Health, of the approximately 933,000 men 16 years of age and older living in Metro Vancouver, it is estimated that 27,000 have sex with other men, representing about 2.9 per cent of the population.
Why did you estimate the MSM population instead of the size of the gay male population?
MSM describes a behaviour whereas terms like gay or bisexual describe an identity. Sexual orientation is made up of three dimensions: a person’s sexual identity, sexual behaviour and attraction. These three dimensions are not always congruent, sometimes our behaviour is different than our identity or attraction.
In HIV research, MSM is commonly used because there is increased HIV risk associated with this behaviour. MSM are disproportionately affected by HIV around the world and locally here in Vancouver. They constitute a large proportion of both people living with HIV and new infections.
One of the strengths of this study is the use of multiple data sources to contribute to the population size estimates, and that the data sources spanned the dimensions of sexual orientation, including identity, behaviour, and attraction measures.
How will the population size information impact public health?
In public health, we need hard numbers. Population size estimates are useful for public health planning, services and implementation. They also lead to a better understanding of the HIV epidemic.
Reliable estimates of the size of the MSM population are necessary to improve understanding of how many people are at risk of acquiring HIV, how many of them are MSM, and what proportion of MSM are living with HIV or have newly acquired HIV. The lack of reliable numbers can impede the work that is being done to reduce HIV risk and the efforts to reach the people who are most vulnerable.
Why don’t we already have a good estimate of the local MSM population size?
There are a number of issues impeding accurate estimates of the size of the MSM population. For one, estimates vary depending on whether an identity, behaviour, or attraction measure is used. Sexual orientation is not currently included in the census, so MSM are not being routinely counted. Also, LGBTQ people may not disclose sexual orientation for fear of stigma and discrimination on other government administered surveys such as the Canadian Community Health Survey, which we used in this study. So, even when LGBTQ people are counted, the numbers may be underestimated.
In light of these challenges, we used a variety of data sources for this study. Using information from Facebook, the estimate of the size of the Metro Vancouver MSM population was as low as 23,800 whereas information from local sexually transmitted infections testing clinics put the number as high as 41,800. The data from our other sources produced estimates anywhere from 10,000 to 30,600. The median of all the estimates is about 27,000.