Associations of sex ratios and male incarceration rates with multiple opposite-sex partners : potential social determinants of HIV/STI transmission

Objectives. Racial/ethnic disparities in heterosexual transmission of human immunodeficiency virus (HIV) and other sexually transmitted infections (STIs) have been hypothesized to be related to the high rate of incarceration and the shortage of men in black communities. This study tested associations of having multiple sex partners with these factors. Methods. Racial/ethnic-specific Census data on the sex ratio and the male incarceration rate were categorized into tertiles and matched with individual data from the National Health and Nutrition Examination Survey 1999–2004 by county of residence for non-Hispanic black, non-Hispanic white, and Mexican American participants. We used logistic regression analyses to examine whether these factors were associated with having multiple opposite-sex partners in the past year. Results. Sex ratios and incarceration rates varied greatly by race/ethnicity; however, we observed significant associations within each racial/ethnic group. Non-Hispanic black men in counties with a greater shortage of males (adjusted odds ratio [AOR] 􀀕 1.9; 95% confidence interval [CI] 1.1, 3.5) and a greater number of incarcerated males (AOR􀀕1.6; 95% CI 1.1, 2.3) in the non-Hispanic black population had significantly greater odds of having two or more partners. Those in two low sex-ratio categories (AOR􀀕2.4; 95% CI 1.0, 5.8 and AOR􀀕4.1; 95% CI 1.6, 10.0) and one high incarceration-rate category (AOR􀀕2.1; 95% CI 1.2, 3.6) had significantly greater odds of having five or more partners. Conclusion. Sex ratios and incarceration rates were associated with the number of opposite-sex partners in some groups. Because the risk of HIV/ STI transmission depends, in part, on the number of partners, it is important to determine the causal relationships among these associations to help better understand racial/ethnic HIV/STI disparities and improve prevention programs and interventions.