Sexually transmitted infections (STIs) remain a sig-
nificant public health problem worldwide. We aimed to describe
the temporal trends and relative contributions of established risk
factors to STIs among sexual health center attendees. This ret-
rospective study included more than 90,000 individuals who
attended a sexual health center in Sydney, Australia, during the
period 1998–2013. Multivariable logistic regression models
were used to identify the correlates of STI diagnoses for three
groups: men who have sex with men (MSM), heterosexual men,
and women separately. Trends in population attributable risk
percentages (PAR%) were estimated to assess the relative con-
tributions of the risk factors on STI diagnosis. STI diagnosis rates
among sexual health clinic attendees increased by 75% from 16
to 28% among MSM and more than doubled among heterosex-
ual men and women (7–15 and 5–12%, respectively). Inconsis-
tent condom use, three or more sex partners, sex overseas, past
STI diagnosis, and contact with an STI case collectively con-
tributed 61, 74 and 55% of the STI diagnoses among MSM,
heterosexual men and women, respectively. Increase in STI diag-
nosis associated with temporal trends in combined risk factors
including condomless sex, multiple sex partners, past STI diag-
nosis, and contact with an STI case. Although the majority of the
factors considered in this study have been significantly associated
with STI positivity in all three groups, their overall population
level contributions to the epidemic have changed substantially.
Ourresultsindicatedsignificant disparitiesbetweentheMSMand
heterosexual men and women as well as sex-specific differences
in terms of sexual behaviors.

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• Temporal Trends in Population Level Impacts of Risk Factors for Sexually Transmitted Infections Among Men Who Have Sex with Men, Heterosexual Men, and Women: Disparities by Sexual Identity (1998–2013)