A total of 924 FSWs were enrolled in Tijuana (N = 474) and in Cd. Juarez (N = 450). Median age was 32 years. Most women were relatively uneducated with a median of 6 years of formal education, and a minority (20%) spoke English. One-quarter of women (24%) were married; however, the majority (94%) had children (). The median number of years spent as a sex worker was 4 years. The median age that women entered sex work was 26 years. More than half (55%) reported they were streetwalkers, whereas the remainder worked in bars, hotels, motels, or other venues.
Sociodemographic and Behavioral Characteristics of FSWs With and Without US Clients
Of the 924 FSWs enrolled, 634 (69%) reported having at least 1 US client, with 41.8% reporting a few, 12.9% reporting some, 12.7% reporting most, and 1.3% reporting that all their clients were from the United States. A higher proportion of FSWs in Tijuana had 1 or more US clients compared with FSWs in Cd. Juarez (78.1% vs. 58.7%, P <0.001). Compared with FSWs without US clients, those with US clients were significantly younger (median = 31 vs. 36 years of age, P <0.001; OR = 0.95 per year). Those with US clients were more likely to live in Tijuana versus Cd. Juarez (58% vs. 36%, P <0.001; OR = 2.51), speak English (25% vs. 7%, P <0.001; OR = 4.33), be more educated (OR = 1.21), and to have entered sex work at a younger age (25 vs. 28 years; OR = 0.94).
A risky pattern of drug use, and their clients’ drug use, was apparent among FSWs with US clients. Overall, 12% of FSWs reported they injected drugs within the last month, 14% often or always used drugs before or during sex, 73% had clients who used drugs, 32% had clients who injected drugs, and 90% reported that other FSWs they worked with used drugs or alcohol with their clients. Compared with those without US clients, FSWs with US clients were more likely to have injected drugs (16% vs. 5%, P <0.001; OR = 3.68), and were more likely to report often or always using drugs before sex with their clients (18% vs. 7%, P <0.001; OR = 3.4). However, they were not more likely to often use alcohol before or during sex with their clients (22% vs. 25%, P = 0.31; OR = 0.84). FSWs with US clients were more likely to report that their clients used drugs (81% vs. 55%, P <0.001; OR = 3.55), or injected drugs (36% vs. 21%, P <0.001; OR = 2.20), and were more likely to report that their fellow sex workers often used drugs or alcohol with their clients (92% vs. 86%, P = 0.006; OR = 1.88).
A mixed picture of sexual risks emerged ( and ). FSWs with US clients were less likely to primarily work out of a hotel or motel (OR = 0.57) compared with other FSWs. FSWs with US clients reported the same median number of clients in the previous 6 months (i.e., 240), but reported having fewer unprotected vaginal sex acts in the last month (13 vs. 16 unprotected acts, P = 0.02; OR = 0.76 for >15 unprotected sex acts in the previous month). FSWs with US clients were paid more per unprotected vaginal sex act ($30 vs. $20, P <0.001; OR = 2.42 for $30 or more earned on average without a condom) compared with their counterparts without US clients. The odds of being an FSW with US clients were 11% higher for each $10 increase in price paid for unprotected vaginal sex act.
Characteristics of FSWs With US Clients: Univariate Logistic Regression
In contrast to their reports of having less unprotected vaginal sex, FSWs with US clients were more likely to test positive for gonorrhea (8% vs. 2%, P <0.001; OR = 4.38) or syphilis with titers ≥1:8 (16% vs. 10% P = 0.008; OR = 1.81) compared with FSWs with no US clients. Although the odds of testing positive for chlamydia or HIV did not differ between FSWs with US clients versus those without, FSWs with US clients were significantly more likely to test positive for at least 1 of these 4 STIs (30% vs. 20%, P = 0.001).
Seven factors entered into our final multivariate model, controlling for site (). Overall, the factor most strongly associated with having US clients was speaking English. FSWs who spoke English were 3 times more likely to have US clients. The odds of having US clients were twice as high for women who lived in Tijuana or injected drugs. FSWs with US clients were also more likely to have syphilis titers ≥1:8 (OR = 1.66), to have more than 250 clients in the past 6 months (OR = 1.54), to be paid more money for sex without a condom versus with a condom (OR = 1.07 per $10 USD increase), and to be younger (OR = 0.95 per year increase in age). Factors that were not independently associated with having US clients included having children, being born in state where they now live, education, marital status, age at initiation into sex work, number of years in the sex trade, often or always used alcohol or drugs before or during sex, having clients who use or inject drugs, having fellow FSWs who use drugs or alcohol with their clients, describing oneself as a street worker, main workplace being a bar, streets, or hotel or motel, price earned with and without a condom, having >15 unprotected vaginal sex acts in last month, and testing positive for gonorrhea, Chlamydia, or HIV.
Factors Independently Associated With Having US Clients Among FSWs in Tijuana and Cd. Juarez
Since FSWs in Tijuana were significantly more likely to report having US clients than those in Cd. Juarez, we reran regression models stratifying by study site (). In both cities, FSWs who were younger and those who had injected drugs were significantly more likely to report having US clients. In Tijuana, additional factors independently associated with having US clients included syphilis titers ≥1:8, being paid more money for sex without a condom, and having greater numbers of clients, whereas speaking English was an independent predictor only for Cd. Juarez.