Partnership-based sexual behaviours among adults in Singapore: a cross-sectional population survey

Introduction Sexual behaviour data are essential for monitoring sexual behavioural trends and designing effective sexual health interventions. In Singapore and other Southeast Asian countries, where research has largely focused on key populations, this study aimed to characterise sexual behaviour patterns in the general adult population and their associations with socio-demographics, engagement with sex workers and sexually transmitted infection (STI) positivity. Methods We conducted a nationwide cross-sectional survey (September 2023 to July 2024) using voluntary response sampling among adults aged ≥21 years, collecting data on socio-demographics and sexual behaviours in the past year, 6 months and 3 months. Partner numbers and sexual activity frequency were modelled using a Lomax distribution across partnered activities (mutual masturbation, oral, vaginal sex and anal sex), and associations with socio-demographics, sex worker engagement and self-reported STI positivity were evaluated using logistic regression. Results Among the 2297 eligible participants, 51.5% were male (1183) and 95.6% were aged 21–60 years (2195). Individuals reporting same-sex partners were more likely to have five or more same-sex partners in the past year. The model-estimated prevalence of engaging with sex workers among individuals aged 21–60 years in Singapore was 4.7% (95% CI 3.7 to 6.2) for females and 18.1% (95% CI 16.1 to 20.4) for males, with higher odds among those with at least five partners in the past year (eg, vaginal sex AOR=7.40, 95% CI 4.03 to 13.58). Self-reported STI positivity was associated with having at least five partners in the past year (eg, vaginal sex AOR=5.03, 95% CI 1.44 to 17.61) and ever engaging with sex workers (eg, vaginal sex AOR=3.16, 95% CI 1.67 to 5.99), but not with barrier protection frequency. Conclusions Patterns varied by sex, sexual orientation and risk behaviours, underscoring the need for context-specific behavioural data to inform STI modelling and public health interventions.