The health effects of vaginal douching have been a concern for a century.1 Anecdotal evidence before the 1950s suggested that douching might cause pelvic inflammatory disease.2 Recent literature reviews have linked vaginal douching not only to pelvic inflammatory disease3 but also to bacterial vaginosis.4 Despite the fact that several cross-sectional studies have shown that frequent douching is associated with bacterial vaginosis,5–9 it remains uncertain whether douching causes bacterial vaginosis or whether women douche in response to symptoms of bacterial vaginosis. A recent longitudinal study failed to find a consistent effect of douching on vaginal microflora and risk of bacterial vaginosis.10 Furthermore, relevant variables such as frequency of douching and type of douche have not been adequately studied in relation to the risk of bacterial vaginosis. Although 27% of women in the United States are reported to douche regularly,11 studies have shown that frequent douching (once per week or more) accounts for a small percentage of all douching women in most populations.9,12,13 Is douching less than once per week also associated with bacterial vaginosis? We examined this question using data from our Feminine Hygiene Practices project.
MATERIALS AND METHODS
From 1999 to 2001, we screened 605 African-American women aged 18–45 years who were visiting gynecologic or family planning clinics of 2 hospitals in New York City and who were potentially interested in participating in our study. Excluded were women who: were pregnant, postpartum, or menopausal; had used antibiotics in the past 2 weeks; had a genital tumor or immunodeficiency disease; were taking medicine having immunosuppressive effects (eg, corticosteroids, azathioprine, cyclosporin); and had either diabetes, hysterectomy, bilateral oophorectomy, recurrent, or chronic vaginitis (defined as having been treated with antibiotics for the same type of vaginitis within the previous 3 months).
A total of 411 women were eligible for the study. After having signed a consent form, the subjects were interviewed by a trained interviewer with a structured questionnaire at the time of their clinic visit. The questionnaire was tested in a focus group of women with a similar background to that of the study population. Information collected in the interview included sociodemographic characteristics, general health and medical history, gynecologic and reproductive history, sexual activity and contraception, assessment of recent life stress, smoking and alcohol use, and feminine hygiene practices. The subjects received a pelvic examination by a gynecologist. The physicians first asked the subjects about clinical symptoms and severity, including vaginal discharge, vaginal odor, vulvovaginal burning or itching, painful urination, and pelvic pain. Pathologic signs of the vagina, cervix, uterus, and adnexa were recorded on a standardized form. Also recorded were the amount of vaginal discharge and its consistency and color. Physicians were blinded to the interview information. Vaginal samples were collected for culture of Candida and trichomonads and for a DNA probe test to detect Neisseria gonorrhoeae and Chlamydia trachomatis. A vaginal swab was used to make a smear and Gram-stained. We used a scoring system for Gram stain diagnosis of bacterial vaginosis created by Nugent et al.14 Gram stain score of 7 or greater was considered bacterial vaginosis positive. This project was approved by the Institutional Review Boards at the Mount Sinai School of Medicine and North General Hospital.
For data analysis, we first examined the women's characteristics in relation to bacterial vaginosis. Categorical variables were tested with χ2, and Student t tests were used for continuous variables. Because the prevalence of bacterial vaginosis is high, we used binomial log-linear models to examine the adjusted prevalence ratio of bacterial vaginosis by frequency of douching, controlling for several potential confounders.15 A factor that is associated with both bacterial vaginosis and douching and is not in the causal pathway was considered a potential confounder. Finally, we examined various douching behaviors and their relationship to bacterial vaginosis.
Among the 411 women who participated in the study, 43 had gonorrhea or trichomonal infection, and an additional 8 women did not have Gram stain slides. These subjects were excluded, leaving 360 women for the final analysis. No significant differences in women's characteristics were identified between 2 participating hospitals. Approximately 88% of our subjects came to the hospitals for routine gynecologic checkup or family planning (Table 1). Most women were unmarried, multiparous, and had 1 or no sexual partner in the past 3 months. The mean age was 30 years, and mean body mass index was 29. Of the 360 women, 52% never douched; 33% douched once per month or less; and 13% douched 2–3 times per month. Only 2% douched once per week or more. The prevalence of bacterial vaginosis in this population was 27% (97/360).
Table 2 presents the patterns of douching practice. More than one half of the women douched after their menstrual period. Eleven percent of women douched to remove vaginal symptoms such as odor, discharge, or itching. The vast majority of women used a water-vinegar solution; only a few used a medicated douche. More than 90% of douching women took a sitting or standing position while douching and douched for less than 5 minutes.
Table 3 shows the crude and adjusted prevalence ratios of bacterial vaginosis by frequency of douching. Douching less than once per week was not associated with bacterial vaginosis. However, frequent douching had a prevalence ratio of 2.35 (95% confidence interval [CI] 0.98–5.63).
Abma et al11 reported from the National Survey of Family Growth that 55% of African-American women douched regularly in 1995, which was consistent with our findings (48%). However, that study did not show the frequency of douching. We found in our population that the vast majority of women douched infrequently; only 2% douched once per week or more. Among those who douched at least weekly, the prevalence of bacterial vaginosis appeared to be higher. However, the causality of the association cannot be established due to the cross-sectional nature of the study. In addition, the CI included 1.0 due to the small number of subjects douching frequently.
In contrast to frequent douching, douching less than once per week was not associated with bacterial vaginosis in our population. This is consistent with the study by Ness et al8 in which women who douched less than once per month had no increased risk of bacterial vaginosis (adjusted OR = 1.0, 95% CI 0.6–1.7). Our study further shows that regular, infrequent douching is often restricted to douching after menses, which suggests that infrequent douching is unlikely to be in response to vaginal symptoms. We found that the overwhelming majority of the subjects in our study used a water-vinegar solution rather than a medicated douche.
Lactobacilli are the predominant bacteria in normal vaginal flora. They produce lactic acid to maintain an acidic environment (pH of 4.5 or less in normal vagina), and some species produce hydrogen peroxide.4 Both low pH and hydrogen peroxide are inhospitable to many pathogenic indigenous microorganisms and exogenous pathogens. Therefore, concerns have been raised that douching may wash away lactobacilli and protective factors and weaken the defense system in the vaginal ecology.4
Several in vitro and in vivo experiments in humans have examined how douching affects vaginal pH and microflora. Juliano et al16 and Pavlova and Tao17 evaluated several commercial douches on vaginal flora in vitro. Both studies found that antiseptic-containing douches showed a strong inhibitory effect against all vaginal microorganisms, including lactobacilli. However, vinegar-containing douches selectively inhibited vaginal pathogens associated with vaginal infection, but not lactobacilli.17
In vivo studies in humans produced similar findings. Onderdonk et al18 found that povidone-iodine preparation resulted in both dramatic acute changes in vaginal flora and potential longer-term effects after repetitive use. They postulated that the bactericidal effect of povidone-iodine might facilitate an overgrowth of organisms with faster growth rates than lactobacilli. A study by Monif et al19 confirmed that povidone-iodine solution produced a dramatic decrease in total number of bacteria in the first 10 minutes after douching. Within 30 to 120 minutes, however, both aerobic and anaerobic bacteria were reestablished to a level near baseline, and lactobacilli were often the first bacteria to recover.
Glynn20 showed that after douching with solutions of acid powder, alkaline powder, and vinegar, vaginal pH returned to predouching levels within 4–5 hours. Later, the author21 had 22 women douche daily for 1 month with douches containing water (n = 5), vinegar (n = 5), acid powder (n = 5), and alkaline detergent powder (n = 7), and an additional 5 control women did not douche. Continued daily douching caused no significant alterations in vaginal pH. In a more recent study, Onderdonk et al18 demonstrated that use of 0.04% vinegar douche caused a transient reduction of total bacterial counts, with most of the reduction attributable to the effect of washing the vaginal surface as noted with physiologic saline. The vaginal flora quickly recovered (less than 4 hours) to the levels measured before douching. The authors concluded that repetitive use of a vinegar solution might not alter vaginal microflora in a biologically important way. These results may explain why douching less than once per week, particularly with vinegar-water solutions, is not associated with bacterial vaginosis in our study.
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