Background: Sexually transmitted infections (STIs) continue to be highly prevalent in young people. New understanding of sexual risk behaviour is essential for future preventive initiatives. Studies based on self-reported STI history indicate that gap length between sexual partnerships is an important determinant in STI transmission, but little is known about the impact of concurrent partnerships and short gap length. This study aimed to examine the significance of concurrent partnerships and short gap length between serially monogamous partnerships in Chlamydia trachomatis-infected individuals compared to the general population.
Methods: A Danish cross-sectional study was conducted among individuals aged 15-29 years with a verified C. trachomatis infection and a sample of the background population. Participants answered a web-based questionnaire on sexual behaviour. Associations were identified in multivariate analyses.
Results: In total, 36% of the included young adults reported that they had two or more partners within the last year. Concurrent partnerships were frequent (46%), and the gap length between serially monogamous partnerships tended to be short (median gap length, 64 days, interquartile interval (IQI) = 31, 122). A strong association was found between concurrent partnerships (odds ratio (OR) = 12.5, 95% confidence interval (CI) = 7.7-20.4), short gap length between serially monogamous partnerships (OR = 10.0, 95% CI = 5.7-17.4) and having a verified C. trachomatis infection.
Conclusions: C. trachomatis infection was strongly associated with concurrent partnerships or short gap length between serially monogamous partnerships. These findings have considerable implications for public health policy. Both types of risk factors should be considered in future preventive interventions aiming to reduce the spread of C. trachomatis infections.
Keywords: Chlamydia trachomatis; sexual behaviour; sexual partners; sexually transmitted infections; young adults.