Buffering Syndemic Effects in a Sexual Risk-Reduction Intervention for Male Clients of Female Sex Workers: Results From a Randomized Controlled Trial.

Objectives: We sought to test the efficacy of a sexual risk intervention for male clients of female sex workers (FSWs) and examine whether efficacy was moderated by syndemic risk.

Methods: From 2010 to 2014, we conducted a 2-arm randomized controlled trial (60-minute, theory-based, safer sex intervention versus a didactic time-equivalent attention control) that included 400 male clients of FSWs on the US-Mexico border with follow-up at 4, 8, and 12 months. We measured 5 syndemic risk factors, including substance use and depression. Primary outcomes were sexually transmitted infections incidence and total unprotected sex with FSWs.

Results: Although participants in both groups became safer, there was no significant difference in behavior change between groups. However, baseline syndemic risk moderated intervention efficacy. At baseline, there was a positive association between syndemic risk and unprotected sex. Then at 12 months, longitudinal analyses showed the association depended on intervention participation (B = -0.71; 95% confidence interval [CI] = -1.22, -0.20; P = .007). Among control participants there still existed this modest association (B = 0.36; 95% CI = -0.49, 1.22; P = .09); among intervention participants there was a significant negative association (B = -0.35; 95% CI = -0.63, -0.06; P = .02).

Conclusion: A brief intervention might attenuate syndemic risks among clients of FSWs. Other populations experiencing syndemic problems may also benefit from such programs.