Background:
Concurrent sexual partnerships are hypothesized to facilitate STD/HIV transmission within populations.

Objective:
To examine factors associated with recent self-reported concurrent partnerships (CP) among men who have sex with men (MSM).

Method:
MSM attending the San Francisco municipal STD clinic completed a survey regarding CP which was linked to their clinic medical records. Analysis was restricted to MSM reporting at least 2 anal sex partners in the past 6 months. CP was defined as having at least one anal sex partner who overlapped another in the past 6 months. Factors including demographics, drug use, reason for clinic visit, numbers of sex partners and unprotected sex acts, STD diagnosis, HIV serostatus, and HIV serosorting (unprotected anal sex with only partners of the same HIV status) in the prior 3 months were examined for associations with CP using univariate and multivariate logistic regression models. Adjusted (AOR) and 95% confidence limits intervals (CI) were calculated.

Result:
Three-hundred eleven MSM were included in the analysis; 182 (58.5%) reported CP. Independent risk factors for CP included being white (compared to non-white) [AOR=2.1 ( 95% CI 1.2-3.5)], using any alcohol in the past 3 months [AOR=4.4( 95% CI 1.2-15.9)], symptoms not being a reason for clinic visit [AOR=2.3(95% CI 1.3-3.8)], being HIV+[AOR=1.87 (95% CI 1.0-3.5)] and serosorting [AOR=1.7 (1.0-3.0)]. A same day diagnosis of syphilis, gonorrhea or chlamydia was not associated with CP; 23% of MSM with CP were diagnosed with an STD compared to 20% of those without CP.

Conclusion:
Among MSM who reported more than two sex partners seen at the San Francisco municipal STD clinic, concurrency was associated with HIV serostatus and serosorting. These data showed no increased risk for STD at the day of clinic visit in this population.

Implications:
The role of concurrency in STI/HIV risk is yet unclear.