Biological and Behavioral Risks for Incident Chlamydia trachomatis Infection in a Prospective Cohort

Abstract

Objective To identify biological and behavioral risks for incident Chlamydia trachomatis among a prospective cohort of young women followed frequently. Methods Our cohort of 629 women from two outpatient sites was seen every 4 months (October 2000 through April 2012) for behavioral interviews and infection testing. C trachomatis was tested annually, and anytime patients reported symptoms or possible exposure using commercial nucleic acid amplification tests. Analyses excluded baseline prevalent C trachomatis infections. Risk factors for incident C trachomatis were assessed using Cox proportional hazards models. Significant risks (p<0.10) from bivariate models were entered in a multivariate model, adjusted for four covariates chosen a priori (age, race or ethnicity, condom use, study site). Backwards step-wise elimination produced a final parsimonious model retaining significant variables (p<0.05) and the four adjustment variables. Results The 629 women attended 9,594 total visits. Median follow-up time was 6.9 years (interquartile range 3.2-9.8), during which 97 (15%) women had incident C trachomatis . In the final multivariate model, incident C trachomatis was independently associated with HPV at the preceding visit (p<0.01), smoking (p=0.02), and weekly use of substances besides alcohol and marijuana (p<0.01) since prior visit. Among 207 women with available colpophotographs (1,742 visits), cervical ectopy was not a significant risk factor (p range=0.16-0.39 for ectopy as continuous and ordinal variables). Conclusion Novel risks for C trachomatis include preceding HPV, smoking, and substance use, which may reflect both biological and behavioral mechanisms of risk, such as immune modulation, higher-risk sexual networks, or both. Improved understanding of the biological bases for C trachomatis risk would inform our strategies for C trachomatis control.

Risk Factors for Incident and Redetected Chlamydia trachomatis Infection in Women

“…Another potential explanation is that women with lower socioeconomic status may be less likely to participate in CT screening. 31 In line with Aghaizu et al 7 and Hwang et al, 11 we found that women with a high-risk HPV infection at baseline were at increased risk for incident CT infection. In our study, this association remained after controlling for number of sexual partners and condom use, indicating that the increased risk of CT infection was not explained by more risk-taking sexual behavior among the HPV-positive women.…”

“…Furthermore, inconsistent findings may be caused by the potentially complex interactions between condom use and risk-taking sexual behavior of the women and their partners. 11 Regarding educational level, we found that women with low educational level were at higher risk for incident CT infection, and this association remained after adjusting for age and sexual behavior. Similar results were obtained in other studies, but these estimates were not adjusted for potential confounders.…”

“…Based on previous findings, 11 we hypothesized that the effect of condom use on CT infection may depend on number of recent sexual partners. We therefore also investigated the effect of condom use separately for women with 1 and more than 1 partners during follow-up.…”

“…Based on previous studies, 7,[9][10][11]13,20 we a priori hypothesized that the risk for incident or redetected CT infection may be affected by the woman's age, educational level, age at sexual debut, number of sexual partners during follow-up, condom use, oral contraceptive use, smoking, and high-risk HPV status. In the main analysis, all potential risk factors were measured at baseline, except for "number of sexual partners during follow-up," which was measured at follow-up.…”

“…23,24 In addition, it was recently found that having an HPV infection may also increase the risk for incident CT infection. 7,11 Conversely, in the few available studies, no associations have been observed between HPV infection and CT persistence 20 or recurrence. 7 In the present study, we investigated risk factors for incident and redetected CT infection, including the role of highrisk HPV, in a population-based cohort of nearly 8000 young Danish women.…”