An exploratory intersectional analysis of lifetime syphilis prevalence among people who inject drugs in Montreal, Canada.

BACKGROUND

Syphilis cases have increased among women and heterosexual men in Canada and people who inject drugs (PWID) are an emerging group at risk of infection. We aimed to examine syphilis prevalence among PWID stratified by men and women, and differences according to intersecting population groups, socio-structural factors and sexual and substance use behaviors.

METHODS

Data were from HEPCO, a community-based cohort study of PWID in Montreal. We tested for syphilis (lifetime and active) via treponemal testing reflexed to non-treponemal testing if positive. Odds ratios were estimated using bivariable exact logistic regression to examine differences in the prevalence of lifetime syphilis infection.

RESULTS

From November 2022 to March 2024, 386 people (16.1% women) had a syphilis test. Thirty-three people (8.6%, 95%CI 6.1,11.8) had evidence of lifetime syphilis infection, of whom two had active syphilis. Lifetime prevalence was significantly higher among men identifying as gay or bisexual, men with HIV, and those who reported recent sex work, condom-less sex, 2 or more sex partners and amphetamine injecting. Among women, prevalence was higher among those who reported recent sex work, recent unstable housing and amphetamine injecting; however, there was no statistically significant difference.

CONCLUSION

Active syphilis infection was uncommon among this cohort of PWID; however, lifetime syphilis infection was almost 9%. Among men in this cohort, evidence indicates that syphilis intersects with other key population group characteristics. More data are needed to better understand syphilis among women who inject drugs. Periodic syphilis testing among PWID may be justified alongside testing for other sexually transmissible and blood borne infections.