In Poisson multiple regression analyses , sex ( risk ratio [ RR ] , 4.00 ; 95 % confidence interval [ CI ] , 2.51-6 .39 ) , intimate partner violence ( RR , 1.23 ; 95 % CI , 1.12-1 .35 ) , unprotected sex ( RR , 1.42 ; 95 % CI , 1.09-2 .01 ) , and multiple partners ( RR , 1.70 ; 95 % CI , 1.11-2 .61 ) , but not partner 's age ( RR , 1.00 ; 95 % CI , 0.94-1 .07 ) were associated with incident STD , adjusting for 42-month STD prevalence .