1 Department of Epidemiology, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA.
2 Department of Obstetrics/Gynecologic and Reproductive Science, Division of Reproductive Infectious Disease, Magee-Womens Hospital of UPMC, Pittsburgh, PA.
3 Department of Obstetrics and Gynecology, Division of Medical Surgical Gynecology, University of Alabama School of Medicine, Birmingham, AL.
4 Department of Obstetrics and Gynecology, Medical University of South Carolina, Charleston, SC.
5 Department of Obstetrics and Gynecology, Denver Health Medical Center, Denver, CO.
6 Department of Medicine, Section of Infectious Diseases, Boston Medical Center, Maxwell Finland Laboratory, Boston, MA.
7 Department of Obstetrics and Gynecology, Section of Infectious Diseases, University of California, Davis, CA.
Received for publication June 9, 2004; accepted for publication July 30, 2004.
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ABSTRACT |
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cervicitis; chlamydia; Chlamydia trachomatis; endometritis; Neisseria gonorrhoeae; pelvic inflammatory disease; prospective studies; women
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INTRODUCTION |
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Retrospective and cross-sectional studies have consistently linked douching to PID (27), but these research designs cannot exclude the possibility that douching follows, rather than precedes, the infections that initiate PID since cervicitis or bacterial vaginosis may prompt women to douche to eliminate symptoms. To our knowledge, only one prospective study has been conducted, a clinical trial comparing ongoing douching with cessation of douching (10). After a year of follow-up, incident PID did not differ between these two groups. However, unknown compliance with douching cessation and small numbers of outcomes limit interpretation of this study.
The biology linking douching to PID has been proposed to involve alteration of the number and type of microorganisms inhabiting the vaginal microenvironment, creating a milieu that favors mixed facultative aerobes and anaerobes over the usually predominant hydrogen-peroxide-producing lactobacilli (11). Douching is consistently associated with bacterial vaginosis (1216). Whether bacterial vaginosis facilitates acquisition of Neisseria gonorrhoeae or Chlamydia trachomatis, or their ascendance into the upper genital tract to cause PID, is not well established (16, 17).
The current investigation was a multicenter, prospective observational cohort study designed to examine whether, among women at high risk for sexually transmitted infections, douching is associated with the acquisition of gonococcal and chlamydial lower genital tract infection and the development of PID.
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MATERIALS AND METHODS |
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Enrolled versus eligible, nonenrolled women were more likely to have risk factors for PID including age 24 years or less (74.8 percent vs. 67.1 percent; p = 0.002) and two or more sexual partners in the past 2 months (53.8 percent vs. 36.7 percent; p < 0.001). They were less likely to be African American (76.1 percent vs. 79.9 percent; p = 0.001) and did not differ significantly in number of previous pregnancies or douching status.
Douching
In a standardized 20-minute interview conducted by trained research staff at each center at baseline and then every 6 months, women were asked about demographic, lifestyle, and medical information. Many of these questions focused on reasons for douching, frequency of douching in the past 2 months, and the most recent product used. Reported reasons for douching (with multiple selections possible) included douching after menses (66.5 percent), for general hygiene (43.6 percent), before/after sexual intercourse (36.7 percent), to reduce vaginal odor (26.9 percent), because "its normal to douche" (19.4 percent), and for abnormal vaginal discharge (6.4 percent) (19). The duration of douching was 2 or more years for 83.5 percent of women who douched (19). Frequency data were categorized as in previous studies as none, once per month, and two or more times per month (2, 17). We did not separately analyze douching products because 87 percent of douchers reported using one of two major brands consisting of similar ingredients: purified water, sodium citrate, citric acid, vinegar, diazolidinyl urea, octoxynol-9, cetylpyridinium chloride, and disodium ethylenediaminetetraacetic acid; or purified water, vinegar, benzoic acid, "lemon mist," octoxynol-9, citric acid, sodium benzoate, disodium ethylenediaminetetraacetic acid, and fragrance. Only 10 women (1.9 percent of women who douched) used medicated douches. The 4-year rates of PID were similar for women using the first major store brand (9.9 percent), the second store brand (11.0 percent), and other douching products (log-rank test; p = 0.89).
Women were also asked about demographic factors including age, race, education, income, and gravidity. They also reported relevant lifestyle behaviors such as tobacco smoking, number of sexual partners in the past 2 months, acquisition of a new sexual partner in the past 2 months, contraceptive use, and sex during menses. Furthermore, they were requested to recall past episodes of sexually transmitted infections including PID and gonococcal and/or chlamydial genital infections. To elicit a history of PID, women were asked, "Has a doctor or nurse ever told you that you had a pelvic infection, pelvic inflammatory disease or PID? This is also known as an infection of the tubes, ovaries, or womb or pus tubes."
Gonococcal/chlamydial lower genital tract infection and bacterial vaginosis
Educated by study staff at baseline on a standardized method for self-collecting vaginal specimens using a cotton swab applicator, subjects collected specimens every 612 months. The correlation between self-obtained vaginal swab specimens and clinician-obtained specimens for detection of C. trachomatis and bacterial vaginosis has been excellent (20, 21). DNA amplification for N. gonorrhoeae and C. trachomatis was performed by using Strand Displacement Amplification (SDA) (Becton, Dickinson and Company, Franklin Lakes, New Jersey) from self-obtained vaginal swabs. For the first 450 women, SDA testing of urine was also accomplished and was found to correlate with vaginal swab SDA 100 percent of the time. All positive test results for gonococcal or chlamydial infection were reported to the clinical sites within 1 week of testing, where appropriate antibiotics were prescribed.
Vaginal swabs were smeared onto slides by study staff at the bedside, and these slides were air dried and later Gram stained at a centralized microbiology laboratory under the direction of one of the authors (S. L. H.). A score of 010 was assigned in light of the relative proportions of large Gram-positive rods (lactobacilli), small Gram-negative or Gram-variable rods (Bacteroides or Gardnerella), and curved Gram-variable rods (Mobiluncus) (22). The results were interpreted by using a standardized method for diagnosing bacterial vaginosis, as described by Nugent et al. (22). A score of 03 was interpreted as consistent with normal vaginal flora, a score of 46 was designated as intermediate flora, and a score of 710 was considered bacterial vaginosis.
PID
To detect PID, women who experienced pelvic pain at any point in the study and women who tested positive on N. gonorrhoeae or C. trachomatis screening (excluding the baseline screen) were scheduled for an additional symptomatic visit involving a pelvic examination and an endometrial biopsy. PID was categorized upon finding 1) endometritis, a histologic diagnosis based on a modification (23) of the criteria proposed by Kiviat et al. (24) involving identification of at least five neutrophils in the endometrial surface epithelium, in the absence of menstrual endometrium and/or at least two plasma cells in the endometrial stroma on a hematoxylin and eosin-stained and methyl green pyroninestained endometrial tissue slide; or 2) the presence of all of the following: a complaint of pelvic discomfort of less than 4 weeks duration; a pelvic tenderness score, using the McCormack scale (25), of one or more; and the presence of oral temperature >38.3°C, leukorrhea or mucopus, erythrocyte sedimentation rate >15 mm/hour, white blood cell count >10,000, or gonococcal or chlamydial cervicitis (26). In secondary analyses designed to test the robustness of our primary categorization schema, we refined PID to require first, a pelvic tenderness score of three or more (rather than one or more); second, endometritis alone defined by at least five neutrophils and/or at least two plasma cells per endometrial tissue slide; and third, endometritis alone defined by at least five neutrophils plus at least two plasma cells per slide.
Follow-up
Of the 1,199 study subjects, 29 (2.4 percent) had a baseline visit only. Among the remaining 1,170 subjects, the median length of follow-up was 3.0 years (interquartile range: 2.43.4 years). The median number of follow-up visits was six (interquartile range: 57 visits). Overall, the median length of follow-up was slightly, yet significantly (p < 0.001) shorter for subjects who reported not douching at baseline (2.9 years) compared with those who reported douching once per month (3.0 years) and those who reported douching two or more times per month (3.1 years). Eighty-eight percent of women were interviewed at their final regularly scheduled contact.
Statistical analysis
The effect of douching on study participants was based on three types of exposure classifications: 1) initial baseline status, 2) time-varying acute effect, and 3) time-varying chronic effect. All analyses were conducted by using the SAS System for Windows, version 8.02 (SAS Institute, Inc., Cary, North Carolina). For initial status, analyzed at the subject level, differences in the frequency of douching (none, once per month, 2 times per month) by baseline characteristics were compared by using chi-square tests. Incidence rates of event-free survival (no PID, gonococcal, and/or chlamydial infection) over 4 years of follow-up by initial douching status were estimated by using the Kaplan-Meier method and were compared by using the log-rank statistic. The log-rank test consisted of a test for homogeneity among the three survival curves with 2 degrees of freedom. Subjects who did not experience the clinical event of interest were censored at the last date of follow-up. Cox regression analysis was used to estimate unadjusted and adjusted hazard ratios of clinical events by initial douching status, including within subgroups (age 1324 years, age
25 years, African American, White, normal baseline vaginal flora, intermediate flora/bacterial vaginosis,
1 sexual partner in the past 2 months,
2 sexual partners in the past 2 months). Covariates selected for adjustment included those that resulted in a change of 10 percent or more in parameter estimates from unadjusted models (27) and those considered biologically relevant. The proportional hazards assumption of invariant relative risk over follow-up was assessed and found to be satisfactory. Clinical site findings were assessed and found not to be substantially heterogeneous.
Discrete-time proportional hazards models (28) fit by pooled logistic regression (29) were used to assess the time-varying impact of douching status on acute risk of PID and gonococcal/chlamydial genital infection. With this method, analyzed at the visit level, douching status reported from scheduled visits was specified as a time-dependent covariate. The "critical exposure" visit to estimate an acute effect from douching was considered the visit that immediately preceded the diagnosis of PID or gonococcal/chlamydial genital infection and that occurred within 6 months of the diagnosis. All other visits by subjects who either did or did not experience the clinical event of interest were considered to represent etiologically irrelevant exposure periods. In instances when multiple visits were conducted within 6 months of diagnosis, the visit more proximal to the diagnosis was considered the critical exposure period. The time-varying effect of chronic douching was assessed by using similar methods, with the exception that exposure classification commenced at the third scheduled visit in order to have sufficient repeated measurements to categorize chronic douching history. With this method, the subjects history of douching was continually updated at each subsequent visit and was scored as the percentage of all visits during which the subject reported douching at least once in the past 2 months (none, 149 percent of the time, 50 percent of the time).
With a priori estimated cumulative incidence rates of 5 percent for PID among nondouching women, the study cohort had 90 percent power to detect a hazard ratio of 2.0 associated with douching, assuming two-sided = 0.05.
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RESULTS |
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Time-varying acute effect of douching
Among 91 women with a documented occurrence of PID, the frequency of reported douching at least once per month at the scheduled visit immediately preceding the diagnosis of PID (median: 21 days, interquartile range: 766 days) was 31.8 percent (28/91) (table 3). This compared with a frequency of 29.1 percent (1,865/6,403) reported at all other visits and by all other women. The corresponding adjusted rate ratio of 0.94 (95 percent CI: 0.58, 1.52) suggested no acute effect associated with douching. A similar lack of an association was observed for the estimated acute risk of douching as related to incident gonococcal/chlamydial genital infection (table 3).
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Secondary analyses
Considering alternative definitions of PID did not change our results. Baseline douching two or more times per month was neither significantly associated with a pelvic tenderness score of four or more (rather than two or more) (adjusted HR = 0.99, 95 percent CI: 0.50, 1.99; n = 62 outcomes) nor endometritis alone (N = 43) defined by at least five neutrophils and/or at least two plasma cells (adjusted HR = 0.88, 95 percent CI: 0.38, 2.06; n = 43 outcomes) or endometritis alone defined by at least five neutrophils plus at least two plasma cells (adjusted HR = 1.27, 95 percent CI: 0.36, 4.44; n = 15 outcomes). Finally, including episodes of PID that were reported by study women but were not validated by a study examination (N = 35) did not result in a significant association between douching two or more times per month and PID (adjusted HR = 1.09, 95 percent CI: 0.68, 1.74).
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DISCUSSION |
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In previous retrospective and cross-sectional studies, the temporal relation between douching and outcomes may have been reversed; that is, symptoms of genital infections may have prompted douching. Biased recall of douching behavior, whereby women knowledgeable of their disease status may have been more likely to report the behavior, may have also accounted for the observed positive relations. To explore this possibility, we analyzed our study as if it were conducted cross-sectionally rather than prospectively (categorizing douching status as that reported at the time of the symptomatic visit) and found an apparent, albeit still nonsignificant, adjusted relation between douching and PID (adjusted odds ratio = 1.56, 95 percent CI: 0.78, 3.12). Moreover, there was a nonsignificant, yet positive association among women with unvalidated symptoms of PID (a categorization based solely on self-report) (adjusted odds ratio = 1.63, 95 percent CI: 0.82, 3.21). Results from the only other published longitudinal study that we are aware of, in which women who douched were assigned randomly to continuation versus a cessation intervention, found no difference in the rate of PID between groups (10).
Our null findings may have resulted from an overly long interval between douching behavior and outcomes. However, most women in the study reported a consistent and ongoing pattern of douching, so that even though reported douching may have preceded the outcome by 6 months, it is likely that within that 6-month window, women were continuing to douche.
Cognizant that our study could neither clearly support nor exclude an association between douching and outcomes in White women (given unstable estimates in this group), we offer possible explanations for the tendency noted throughout the literature toward a race-specific douching effect (2, 4, 7). First, White women in our study were more likely than African-American women to have characteristics known to elevate the risk of PID (19). Therefore, residual confounding may have resulted in a spurious association in White but not African-American women. Second, African-American women may be intrinsically more susceptible to genital infections by virtue of differential colonization by bacterial vaginosis (32). For White women, douching may alter their vaginal microecology and thereby elevate their risk of acquiring gonococcal/chlamydial cervicitis and PID to that inherent in African Americans.
Strengths of our study include the large number of women studied, use of consistent enrollment and data collection protocols, collection of biomarkers of effect, and relatively long-term and complete longitudinal data collection, which permitted assessment of douching history as a time-varying, as well as a fixed, baseline behavioral characteristic. Weaknesses include the observational nature of the study, making it impossible to exclude unmeasured confounding. Furthermore, self-reporting of douching may have led to misclassification. However, this likely did not differ in direction between those developing future PID and those not and therefore would not have been expected to meaningfully bias the relative risk estimates. Screening and timely treatment may have diminished the observed association between douching and PID. Nonetheless, this explanation would neither explain the lack of association found between douching and gonococcal/chlamydial genital infection nor be consistent with the high rates of PID observed. Antibiotic use for nongenital indications could have also resulted in confounding if such antibiotics were effective against genital infections and if antibiotic use was more common among women who douched. Finally, the generalizability of the study is impacted by selection of a high-risk group of predominantly young, African-American women. Nonetheless, in this high-risk group, our data do not support a relation between douching and either gonococcal/chlamydial genital infection or PID.
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ACKNOWLEDGMENTS |
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The authors thank the following persons whose dedication to working with the women enrolled in the GYN Infections Follow-through Study made this study possible: Susie Alagasarmy, Julie Beuler, Debbie Carr, Hope Cohen-Webb, Leslie Curll, Christine Donahue, Amanda Farmer, Janice French, Melissa Girman, Alice Howell, Juliette Hunt, Ellen Klein, Barbara Kolodjiez, Faye LeBoeuf, April Lehman, Rosalyn Liu, Ingrid Macio, Kathleen McKenna, Kim Miller, Megan Mundy, Lori Paladino, Anne Rideout, Jacqueline Travasso, Jennifer Watts, and Casey Zuckerman.
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NOTES |
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REFERENCES |
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