Social and behavioural determinants of syphilis: Modelling based on repeated cross-sectional surveys from 2010 and 2017 among 278,256 men who have sex with men in 31 European countries

Ana Mendez-Lopez; David Stuckler; Ulrich Marcus; Ford Hickson; Teymur Noori; Robert N Whittaker; Klaus Jansen; Asuncion Diaz; Lukasz Henszel; Annie Velter; Jan C Semenza; Axel J Schmidt

doi:10.1016/j.lanepe.2022.100483

Social and behavioural determinants of syphilis: Modelling based on repeated cross-sectional surveys from 2010 and 2017 among 278,256 men who have sex with men in 31 European countries

Lancet Reg Health Eur. 2022 Aug 9:22:100483. doi: 10.1016/j.lanepe.2022.100483. eCollection 2022 Nov.

Authors

Ana Mendez-Lopez¹, David Stuckler², Ulrich Marcus³, Ford Hickson⁴, Teymur Noori⁵, Robert N Whittaker⁶, Klaus Jansen³, Asuncion Diaz⁷, Lukasz Henszel^{8

9}, Annie Velter¹⁰, Jan C Semenza¹¹, Axel J Schmidt⁴

Affiliations

¹ Department of Preventive Medicine, Public Health, and Microbiology, School of Medicine, Autonomous University of Madrid, Spain.
² Dondena Research Centre, Bocconi University, Italy.
³ Department for Infectious Disease Epidemiology, Robert Koch Institute, Berlin, Germany.
⁴ Sigma Research, Department of Public Health, Environments & Society, London School of Hygiene & Tropical Medicine, London, United Kingdom.
⁵ European Centre for Disease Prevention and Control, Stockholm, Sweden.
⁶ Section for respiratory, blood-borne and sexually transmitted infections, Department of Infection Control and Vaccines, Norwegian Institute of Public Health, Norway.
⁷ National Centre of Epidemiology, Instituto de Salud Carlos III. CIBER de Enfermedades Infecciosas (CIBERINFEC), Spain.
⁸ Department of Infectious Disease Epidemiology and Surveillance, National Institute of Public Health - National Institute of Hygiene, Warsaw, Poland.
⁹ Public Health Protection Unit, NHS Greater Glasgow and Clyde, Glasgow, United Kingdom.
¹⁰ Health Promotion and Prevention Division, Santé Publique France, Saint Maurice, France.
¹¹ Heidelberg Institute of Global Health, University of Heidelberg, Germany.

Abstract

Background: Syphilis case notifications among men-who-have-sex-with-men (MSM) have increased markedly over the past two decades in Europe. We tested several potential factors for this resurgence.

Methods: Self-reported data from two cross-sectional waves of the European MSM Internet Survey (EMIS-2010 and EMIS-2017, N = 278,256 participants living in 31 European countries) were used to fit multivariable hierarchical logistic regression models designed to evaluate potential social, behavioural, and interventional determinants of syphilis diagnosis. Additional multivariable hierarchical negative binomial models investigated determinants of the number of non-steady male condomless anal intercourse (CAI) partners. We tested the hypothesis that more CAI and syphilis-screening are associated with syphilis resurgence, both linked to use of pre-exposure prophylaxis (PrEP).

Findings: Between 2010 and 2017, incidence of syphilis diagnosis in the previous 12 months rose from 2.33% (95%CI: 2.26-2.40) of respondents reporting a syphilis diagnosis in 2010 compared with 4.54% (95%CI: 4.42-4.66) in 2017. Major factors contributing to syphilis diagnosis were living with diagnosed HIV (adjusted odds ratio (aOR) 2.67, 95%CI: 2.32-3.07), each additional non-steady male CAI partner (aOR 1.01, 95%CI: 1.01-1.01), recency of STI-screening (previous month vs no screening, aOR 25.76, 95%CI: 18.23-36.41), selling sex (aOR 1.45, 95%CI: 1.27-1.65), and PrEP use (aOR 3.02, 95%CI: 2.30-3.96). Living with diagnosed HIV (adjusted incidence rate ratio (aIRR) 3.91, 95%CI: 3.77-4.05), selling sex (aIRR 4.39, 95%CI: 4.19-4.59), and PrEP use (aIRR 5.82, 95%CI: 5.29-6.41) were associated with a higher number of non-steady male CAI partners. The association between PrEP use and increased chance of syphilis diagnosis was mediated by STI-screening recency and number of non-steady male CAI partners, both substantially higher in 2017 compared to 2010.

Interpretation: Syphilis cases are concentrated in three MSM population groups: HIV-diagnosed, PrEP users, and sex workers. Behavioural and interventional changes, particularly more non-steady male CAI partners and recency of STI-screening, are major contributing factors for increasing syphilis diagnoses among MSM in Europe.

Funding: European Centre for Disease Prevention and Control.

Keywords: Condomless anal intercourse; Europe; Homosexual; MSM; Men who have sex with men; PrEP; Pre-exposure prophylaxis; STI-screening; Survey; Syphilis.