Behavioral Factors Affect Bacterial Vaginosis Risk

OB/GYN News, Sept 1, 2000 by Bruce Jancin

Douching, smoking, increased sexual activity are independent risk factors.

INCLINE VILLAGE, NEV. -- Douching, smoking, and the absence of vaginal lactobacillus emerged as powerful independent risk factors for acquisition of bacterial vaginosis in the first large longitudinal study of this common gynecologic disorder.

Other potent independent risk factors for acquisition of bacterial vaginosis (BV) were black race, increased sexual activity, and having an intermediate as opposed to a normal Gram stain at baseline, Marijane A. Krohn, Ph.D., said at the annual meeting of the Infectious Diseases Society for Obstetrics and Gynecology.

She reported on 1,116 non-pregnant young women enrolled at three Pittsburgh sites, of whom 613 (55%) were BV negative at baseline. During a mean of more than 6 months or a total of 387 woman-years of follow-up at interim analysis in this ongoing National Institutes of Health--sponsored study 26% of the initially By-negative group acquired the infection.

Douching was among the significant risk factors for BV acquisition by univariate analysis. The BV conversion rate among women who routinely douched was 81 cases per 100 woman-years of follow-up, compared with 37 cases per too woman-years in nondouchers, said Dr. Krohn of the University of Pittsburgh.

A woman's age--participants ranged from 18 to 30 years old--had no impact upon risk of BV acquisition. Neither did condom usage or use of spermicide-bearing condoms.

Douching and the other univariate risk factors were then subjected to four different multivariate regression models to determine which factors were independently associated with increased risk of BV acquisition, she said at the meeting, also sponsored by the American College of Obstetricians and Gynecologists.

Using this powerful statistical approach, absence of hydrogen peroxide-producing lactobacillus in the vaginal flora at baseline was associated with a 50%-70% increased risk of acquiring BV during the relatively brief follow-up period after controlling for race, smoking, and douching. Douching, in turn, was associated with a 60% increased risk.

Nonwhite race, with the vast majority of nonwhites in this study being black, entailed a 50%-60% increased risk in the various models. Smoking carried a 70%-100% increased risk. Having an intermediate Gram-stain score at baseline conferred a 3.1-fold increased risk of BV acquisition.

Increased sexual activity as reflected either by having two or more sex partners in the last 4 months, having sex three or more times per week, or having a new sex partner, was associated with a 2-2.5-fold increased risk.

It appears that many risk factors for acquiring BV within the next several months are behavioral in nature, and therefore potentially modifiable. This probably includes lack of vaginal lactobacillus; a study of an investigational vaginally inserted gelatin-coated lactobacillus capsule is now underway.

It's probable, however, that smoking and nonwhite race are surrogate risk markers standing for some other as-yet unidentified factors predisposing to BV acquisition, the investigator said.

Dr. Jack D. Sobel was among the audience members who heaped praise on Dr. Krohn's investigation, calling it "a very important study beautifully done." Reassuringly, the same risk factors for BV acquisition were identified in a recent HIV study that, while much smaller in size, featured a 7-year follow-up, said Dr. Sobel of Wayne State University, Detroit.

BV is characterized by a shift in the vaginal flora from predominantly lactobacillus to anaerobic overgrowth. It is the most common vaginal infection during the childbearing years. Although traditionally dismissed as a nuisance condition, in recent years it has been linked to serious obstetric complications: premature rupture of membranes, preterm labor and birth, chorioamnionitis, and postpartum endometritis. BV has also been associated with gynecologic complications, including pelvic inflammatory disease, cervicitis, and postoperative infection.

Discourage Douching

The practice of douching--linked to acquisition of bacterial vaginosis in Dr. Krohn's study--also came under fire by Dr. David A. Eschenbach, professor of ob.gyn. at the University of Washington, Seattle.

Dr. Eschenbach randomized 36 healthy young volunteers to the use of one of four commercial douching products five times over a 1 month period.

Serial assessment of subjects' vaginal epithelium by colposcopy, biopsy, and culture demonstrated that douching produced transient increases in neutrophils in cervical mucus. Two douching products, one containing baking soda and the other Betadine, were associated with transient increases in Enterococcus. Use of the other two douching products were tied to increased subepithehal neutrophil counts.

Douching, routinely used by many women to cleanse following intercourse or menses, has been linked in prior studies to increased risk of acute pelvic inflammatory disease, ectopic pregnancy primary tubal infertility, and HIV infection. The mucosal and vaginal flora changes demonstrated in this study may figure in the mechanism by which douching causes these effects.