Demographic and baseline characteristics are summarised in . The majority of participants were women (55%) aged 31–40 years old (44%) with a mean age of 36 years. Men were 1 year older in the intervention compared to control condition (35.3 vs 34.2). Almost 88% had less than a high school education and 9% had no education. Almost all women were married (97%), but fewer men were married (87%). About 87% had a regular income. No differences between the two study groups were found in education, marital status or regularly earning money.
Demographic characteristics of participants by intervention and control condition
shows a summary of behavioural and biological outcomes over time by gender and intervention condition. At baseline, only 6.5% of participants reported unprotected extramarital sex in the prior 3 months but about 20% had a STI. The disparity in baseline behavioural risk reports and STI infection rates was greatest among women: about 24% had an STI but only about 2.4% reported unprotected extramarital sex. In stark contrast, 14.4% of men had STIs of whom 11.5% reported unprotected extramarital sex. Unprotected extramarital sex and laboratory confirmed STIs decreased significantly in both intervention and control conditions over time. Results from unadjusted analysis show that the women in the C-POL intervention had a significantly lower rate of STI at 24 months (5.7%) compared to the control (8.3%; Fisher’s exact test, p=0.043). presents the percentage of any new STIs by condition over time for each gender.
Summary of behavioral and biological outcomes by condition
Percentage of any new STIs by condition (intervention and control) and by gender across time (baseline, 12-month, and 24-month follow-ups).
presents results from the Transition Model (model 1) testing the effect of previous STI status on follow-up STI incidence. Participants were less likely to acquire any new STIs if they were men (p<0.0001), older (p=0.0168) or had not previously experienced any STIs (p<0.0001). Participants in both study conditions who did not have a STI at baseline were unlikely to acquire a new STI at either follow-up assessment (<5% for intervention and control). There were significant intervention effects on incident STIs at 24 months among participants with previous STIs: 16.5% in the intervention markets compared to 29.5% in control. Results adjusting for age and gender indicated that the odds of acquiring any new STIs by the 24-month follow-up among those who experienced one or more STIs previously was 50% less in intervention markets compared to control markets (OR 0.47, 95% CI 0.25 to 0.90; p=0.0242). An intervention effect was also observed for women for all STIs (OR 0.44, 95% CI 0.20 to 0.95; p=0.0363) and for bacterial STIs (OR 0.46, 95% CI 0.23 to 0.90; p=0.0242).
Results of biological outcome and bacterial sexually transmitted infections (STIs) by previous STI status
A similar trend was found when the same analytic method was applied to the behavioural outcome of self-reported unprotected extramarital sex. At baseline, participants in both conditions had similar rates of recent unprotected extramarital sex (6.5% intervention and 6.6% control shown in ), which was associated with STI at baseline (p=0.0052). Participants reporting behavioural risk at the 12-month follow-up reported lower rates of risk in the intervention (36%) compared to the control (42%) at the 24-month follow-up.
Finally, we examined the intervention effect on unprotected extramarital sex at the follow-up assessments for low versus high risk participants using model 2, which compares intervention and control participants stratified by their baseline STI status. presents the percentage reporting unprotected extramarital sex by study condition and baseline STI status. Among participants who had not experienced any STIs at baseline, the percentage having unprotected extramarital sex dropped in both conditions from baseline to 24-month follow-up from 5.5% to 3.8% in the intervention (OR 0.75, 95% CI 0.60 to 0.94; p<0.05) and from 6.5% to 3.9% in the control condition (OR 0.65; 95% CI 0.48 to 0.87; p<0.05) with no statistically significant differences in trends between conditions. However, among those who experienced one or more STIs at baseline, the percentage reporting unprotected extramarital sex dropped significantly from 10.7% to 4.5% (58% reduction) in the intervention markets (OR 0.38, 95% CI 0.19 to 0.77; p=0.0067) and non-significantly from 6.9% to 5.7% (17% reduction) in the control markets (OR 0.91, 95% CI 0.47 to 1.79). The control participants were more likely to engage in any unprotected extramarital sex than those in the intervention condition (OR 2.4, 95% CI 0.91 to 6.34; p=0.078) at 24-month follow-up.
Percentage of unprotected sex by treatment and by baseline selected sexually transmitted infections.