In this prospective cohort of HIV-infected and high-risk uninfected adolescent girls and young women followed for a median of three years, douching was an independent risk factor for STI acquisition. This finding supports the hypothesis that regular douching contributes to the risk of STI acquisition among high-risk female adolescents since the douching behaviors measured in this prospective study antedated the incident STI. The study addresses directly one of the principal limitations in much of the douching and health research literature, namely that cross-sectional studies may be measuring increases in women’s douching activities due to their douching in response to STI symptoms, rather than douching having increased the women’s probability of actually acquiring an STI.3,34
We found that the adjusted hazard of STI for female adolescents who always douched was about two times the hazard for those who never douched. The positive findings of this study support the hypothesis that douching and STI acquisition are causally related, namely that prior douching in risk factor for acquiring a subsequent STI.
The advantage and strength of the design of our study is that it allowed prospective examination of the influence of douching behavior on incidence of STIs. Only a few prospective studies have examined douching and STI27,28
Ness et al.
did not find an association between douching and development of a STI among their cohort. 27
Hawes et al.
found evidence of association between douching and bacterial vaginosis, but did not find an association between douching and acquiring a STI.28
Many cross-sectional studies support the relationship between douching and STI5,15,18–20,22–26
while other studies report conflicting results.15,19,30
Some cross-sectional studies suggest the incidence of STIs are highest among women who douche more frequently,3,20,21,26
but other studies show that women who have a history of STIs are less likely to douche.3,7
Annang et al.
found that women who douched during menses and those who douched to alleviate itching were more likely to be infected with C. trachomatis,
while those who douched after sex were less likely to be infected with N. gonorrhoeae.15
Ness et al.
reported in a cross-sectional study that while women with intermediate disturbed vaginal flora (a Nugent score43
of 4 to 6) had a higher prevalence of STI, they did not find that douching was associated with a STI.30
However, Chacko et al.
showed that a history of douching was associated with cervical gonorrheal infection22
and Beck-Sague et al
. showed that douching during the prior month had a significant association with the prevalence of chlamydial infection.23
Our prospective study was underpowered to look at each STI outcome separately which is why we used an aggregate “any of the four STIs” outcome.
A unique aspect to this study was that it followed a cohort of female adolescents. No prospective studies looking at the effects of douching on incidence of STI in female adolescents have been published. Another strength of the study is that results were consistent whether or not those with a STI at baseline in the analysis were included. While the disadvantage of including those with baseline STI is that there could be some intervention altering behavior in the cohort, both analyses provided similar results. We used baseline sexual behavior in our models because sexual behaviors did not change substantially in our cohort of HIV-infected and high risk HIV-uninfected youth, despite intensive educational efforts to reduce high risk behaviors.44
Using the intermittent douching category as a comparison group for the Cox proportional hazards regression analysis was a methodologic concern. Female adolescents in the intermittent douching group were extremely diverse in their douching patterns and not enough detail was obtained in douching behavior in the REACH study to tease out these differences. The advantage of limiting comparisons to female adolescents who always or never douche is that it gives a better idea of consistent douching practices.
In addition to categorizing female adolescents to douching categories using self-reported douching behavior at all follow-up visits, adolescents were categorized using self-reported douching behavior over STI-free follow-up times only. The advantage of the second categorization is that it accounts for the prospective nature of the data by not including post-STI douching behavior. A limitation of this second approach is that female adolescents classified as always douching or never douching have shorter follow-up times. A female who regularly douches is more likely to be classified as always douching if she is only STI-free for a few months of follow-up. The same holds true for a female who rarely douches in being classified as never douching. Using this second method of categorization, many of those classified as never or always douching may actually be females who intermittently douche. Hence, the longer time to STI among intermittent douchers () is likely an artifact of how we defined the intermittent douching category, and implies that the hazard ratio comparing those who always (or never) douche to those who intermittently douche is likely biased. For this reason, we focus on the comparison between those who never douche and those who always douche, where this potential bias is limited. Our study results comparing participants who always versus never douche were consistent whether categorizing douching behavior over all follow-up time or over all STI-free follow-up time.
We found an association between STI at current visit and self-reported douching. However, similar to cross-sectional studies, a limitation of this analysis is that causality is unknown as douching could have been precipitated by the STI itself as a response to discomfort or vaginal discharge. Therefore, we examined the association between douching reported at the current visit and STI at the next visit. We found evidence of an association even after adjusting for STI at the current visit, though this association was weakened when we further adjusted for HIV-status, race, and age. This type of analysis may underestimate the effect of douching on STI as STI at current visit may be on the causal pathway between reported douching at the current visit and STI at the next visit. In other words, douching may lead to STI at current visit which may in turn lead to STI at next visit. By adjusting for STI at current visit, we are being conservative and in essence assuming that STI at current visit were not caused by douching. Therefore, although the adjusted association in this conservative analysis was not strongly statistically significant, the estimated odds ratios are consistent with douching being a risk factor for future STI acquisition.
As this point will not be an obvious one to many readers, we reiterate that by focusing on the association between douching and STI at a future visit after adjusting for STI at current visit, we are in essence assuming that none of the STIs at current visit are caused by douching. That we still see an association, despite this extremely conservative assumption, is evidence consistent with douching being a risk factor for STI. A familiar example can illustrate our point further. Oncogenic types of human papillomavirus (HPV) can lead to cervical cancer that can lead to death. If one adjusts for cervical cancer and estimates the effect of HPV on death, one is adjusting away some or much of its true effect. If HPV is still associated with death, even after adjusting for cervical cancer, then that can be construed as even stronger evidence for an association between HPV and death.
The study had other limitations. The study was conducted in a defined population of female adolescents with high-risk behaviors, two-thirds of whom had HIV infection. The primary finding may not be generalizable to lower-risk adolescent populations with different sociodemographic, immunologic, and/or behavioral characteristics. Also, the study utilized self-report for the main exposure variable to classify the level of douching for each female. The use of ACASI may help decrease social desirability bias, but there may be potential concerns about reliability and accuracy. However, the directness and simplicity of the douching questions may have mitigated any potential misunderstanding of what was meant.39
As with all observational studies, the results could have been influenced by some unmeasured confounding variables.
Because two-thirds of the adolescents in the cohort were HIV-infected, HIV status may have influenced incidence of STI. McClelland et al.
reported that HIV-1 infection was associated with a significantly higher incidence of genital tract infections in commercial sex workers in Kenya.45
In our study, HIV infection status was not a risk factor for STI acquisition, and HIV status did not modify our douching and STI associations.
Given the weight of the evidence in this study, important public health and clinical action is suggested. Public health initiatives are needed to educate adolescent females to not douche and to urge women who douche to modify the behavior. Adolescent girls who douche often start douching for non-medical reasons and that douching behavior is currently being initiated at earlier ages than ever before.46
The most common pro-douching influences are mothers, friends, and relatives.1,2
Many women see douching as a preventative measure. A study of 1500 low-income women in Missouri showed that nearly 10% douched at certain times to try to prevent HIV infection.47
Women who douched were more likely to practice other preventive hygienic activities, such as brushing their teeth or obtaining a Pap smear in one survey in the southeastern U.S.1
Persistence of douching may also be due to aggressive advertising by manufacturers of douching products and the absence of cautionary statements by authoritative medical and public health organizations.2
In a randomized clinical trial in urban Alabama, Grimley et al
. found that douching risk reduction counseling succeeded in reducing douching among 275 mostly black, high risk adolescent girls/young women ages 14–23.45
Given these results, clinical counseling to avoid douching should be considered an appropriate standard of care.45
The weight of the evidence suggests that anti-douching counseling should be provided in multiple venues to reach youth in order to discourage douching. These venues include public health campaigns, school health courses, popular media publications and media programs targeting girls and women (e.g., “Oprah” and “The View”, programs popular at present in 2008), and, importantly, anticipatory counseling by all health professionals who care for pubescent girls, adolescents, and young adults. Given their experience and credibility, gynecologists can provide special leadership in this effort. Future research should assess whether douching also increases risk of other reproductive tract infections and should study how to implement effective douching reduction education in clinical, school, and home venues.