The cohort of women was predominantly young (79% <25 years of age), diverse, and high risk (). Forty-two percent of the cohort reported their race/ethnicity as white/non-Hispanic, 21% as African American/non-Hispanic, and 23% as Hispanic. A quarter had less than a high school education, and 37% had only a high school education. Most participants were not married; 90% were single, never married, and 5% were separated, divorced, or widowed. Almost half of the participants had a history of STI or unplanned pregnancy, 52% had 6 or more lifetime sexual partners, 48% were current cigarette smokers, and 59% reported some illicit drug use in the past years. One in five women reported they always used condoms when they had intercourse.
Characteristics of Women with and without Incident Sexually Transmitted Infections (STI)
Women with reported histories of violence were more likely to report more lifetime sexual partners and illicit drug use than women with no history of violence. Age, history of STI and history of unintended pregnancy, partners in the last month, and current smoking were associated with ever emotional or physical abuse but not recent sexual abuse whereas race/ethnicity was only associated with lifetime report of emotional or physical abuse. Education was associated with abuse in the last year (physical or sexual) but not lifetime emotional or physical abuse.
Incident STIs were common in this cohort. Eighty-seven women (16%) had at least one STI during the 2-year observation period. Women with an incident infection differed significantly from those who did not in a number of ways. Women with incident STIs were more likely to be African American, to be of lower educational level, to have a history of STI or unplanned pregnancy, and to report more sexual partners in the last month. Women with incident STIs were less likely to avoid sexual partners who pressure to have sex without a condom. There were no significant differences between women with an incident STI compared with those without in terms of lifetime sexual partners, current cigarette smoking, illicit drug use, consistent condom use, or age.
We examined three questions related to experiences of interpersonal violence: ever emotionally or physically abused, physical abuse in the past year, and sexual abuse in the past year (). Abuse was common; 46% reported some emotional or physical abuse in their lifetimes, and almost 25% reported physical or sexual abuse in the past year. Of the 1 in 4 women reporting recent abuse, 56% of participants reported only physical abuse, 20% reported only sexual abuse, and 24% reported both physical and sexual abuse. In the bivariate comparisons, recent abuse was more common among women with incident STI; 36% of women with an STI reported abuse in the past year compared with 21% among those without an incident STI (p
0.01). Further breakdown by type of recent abuse found this difference was pronounced only among women who reported only physical abuse in the past year.
We also examined whether the time to incident STI differed by experience of interpersonal violence (). Women with a history of lifetime emotional/physical abuse had consistently faster rates of STI occurrence, but these findings were not statistically significant after adjustment for age, race/ethnicity, education, history of STI, number of sexual partners in the past month, illicit drug use, and avoidance of partners who pressured to have sex without using a condom. Recent abuse, however, was significantly associated with time to incident STI in this cohort. After adjustment for demographic and behavioral characteristics, the risk of STI was almost 70% higher among women who reported recent abuse (hazard rate ratio [HRR] 1.68, 95% CI 1.06, 2.65).
Association between Experiences of Interpersonal Violence and Incident Sexually Transmitted Infections
We sought to determine if type of recent abuse was associated with time to incident STI. Reporting recent physical abuse alone was consistently and significantly associated with time to STI incidence. In the crude analysis, the hazard rate for women who had experienced recent physical abuse only was twice that of women who had not (HRR 2.14, 95% CI 1.27, 3.60). After adjustment for demographic and behavioral characteristics, this finding was attenuated (HRR 1.77, 95% CI 1.03, 3.02). Recent sexual abuse and recent physical and sexual abuse were associated with increased risk of incident STI, but the associations were not statistically significant. Because women may have experienced abuse after the baseline reporting and before contracting an STI, we also examined models that adjusted for any abuse after baseline, but this did not alter the findings appreciably (data not shown). Moreover, as this cohort had been recruited for an intervention study to improve dual contraceptive method use, we also adjusted for initiation of dual method, but the results were unchanged (data not shown).
Demographic characteristics persisted as important risk factors for incident STI. Women with less than a high school education had estimates of HRRs ranging from 1.8 to 2.0 in the adjusted models. Similarly, irrespective of the abuse variable examined, black women had a 3-fold increase in incidence and Hispanic women had a 2-fold increase in incidence compared with white women. Age was not associated with STI incidence, but this is likely a result of the study's enrollment criteria, which sought to enroll older women at high risk for STIs.