In women of childbearing age, BV is the most common vaginal infection and occurs in up to 70% of women. Globally, the prevalence of BV varies considerably between countries, regions, races and ethnic groups. Although antibiotics are recommended as the first-line therapy, 20–30% of women have a recurrence of symptoms after completing the first round of treatment.[16]
Univariate analysis showed that the unemployment and a low educational degree were risk factors for UBV, and particularly, lower educational level was a risk factor for RBV (P1 = 0.0024). The great statistical difference still exited under multivariate logistic regression analysis (P = 0.020). Certain studies have believed that the prevalence of lower reproductive tract infections was higher among people with lower socioeconomic status and lower educational background. An epidemiological study in Brazil also argued that high income was a protective factor for BV [17]. This may be due to women with high socioeconomic status and high educational level have more opportunities to gain a knowledge of preventing BV and other vaginal infectious diseases. Therefore, they could avoid the occurrence of BV effectively. However, there was a lack of clear relationship between BV and patients' age or setting.
Univariate analysis showed that the smoking was a risk factor for RBV(P1 = 0.0303), and the great statistical difference still exited under multivariate logistic regression analysis (P = 0.026). Our results were in accordance with previous literature stating there was a higher number of women who were diagnosed with BV and had smoking habits[18]. This finding could be interpreted as that smoking promotes an antiestrogen environment and elevates vaginal amines, which predisposes women to BV[19]. Besides, tobacco is thought to alter the physiology and structure of the flora of the vagina, increasing bacterial virulence. A previous study found that compared with lean women, overweight and obese women had a higher frequency of BV[20]. While our result revealed that BMI was statistically different among women with RBV, UBV and NVM(P3 = 0.014). While this difference faded away under multivariate analysis.
This was the first time to take diet and sedentary life style into consideration when analyzing the risk factors of BV. Univariate analysis revealed frequent desserts and a sedentary lifestyle were risk factors for BV, and particularly, a sedentary lifestyle was a risk factor for RBV (P1 = 0.0364). While this great statistical difference disappeared under the multivariate logistic regression analysis (P = 0.078). The fact that the anus is close to the vagina anatomically providing much convenience for the migration of gut organisms to the vagina. It is hypothesized that overeating desserts and sweets may disrupt intestinal microflora, leading to the imbalance of vaginal microflora, resulting in becoming chief culprit of RBV. Moreover, a sedentary lifestyle is not beneficial to enhancing the body's immunity, leaving the body a weakened protective immunity, recalcitrance to overgrown anaerobes and the hotbed of RBV.
Besides, this study found no statistical relationship between RBV and the menstruation care, underwear materials, frequency of underwear replacement and bath way. A longitudinal study in Britain also found no significant difference between BV and underwear material and menstrual pads[21]. While backward wiping was a protective factor for UBV, which has never been studied before. The reason may be attributed to the fact that the intestinal microflora on the contaminated toilet paper could pollute the vulva and then disturb the vaginal microflora.
This study hinted that history of other vaginitis and history of HPV infection were risk factors for UBV, consistent with another study which showed that women with BV were twice as likely to acquire trichomonal vaginitis compared with women without BV.[22] Specially, when it comes to history of other vaginitis, there existed a significant statistical difference (P1 = 0.0088). Reproductive history and menstrual cycle had little effect on UBV, but one study found luteal phase to be a protective factor of BV [17]. Many studies hold that use of intrauterine device (IUD) was a risk factor for BV [23, 24]. This is perhaps because the tail of IUD exposed in cervical vagina and vagina provided colonization conditions for anaerobic bacteria. Other studies suggested that the use of contraceptives was a protective factor for BV [17, 25]. This may due to the fact that estrogen increases epithelial glycogen, which can metabolize into lactic acid, with antimicrobial activity against BV-associated bacteria. In view of the small number of women who used contraceptives conventionally, it was unscientific to conduct an analysis between contraceptives and BV here. Also, a study stated that hormonal contraception and condom use were protective against BV[26].
The present study showed that there was no significant relationship between sexual intercourse during menstruation, the frequency of sexual life and RBV. Univariate analysis showed that the age of FSI less than 20 and not cleaning the vulva during sexual activity were risk factors for UBV, but not for RBV. Although BV is not belonging to sexually transmitted disease, it is really associated with unprotected sexual activity[27]. As what this study showed multiple sexual partners increase susceptibility to both RBV and UBV, which was also manifested in another study[1, 26]
Interpretations of findings of this study are to be extrapolated cautiously because of its limitations. The primary drawback was that the sample size was not large enough and the data on smoking, alcohol consumption, number of sexual partners and sexually transmitted diseases was inadequate. Then, the study population was hospital-based and the result might not necessarily be applicable to the whole population. Therefore, community-based studies are needed. Additionally, all responses received on the baseline questionnaire were self-reported and subject to recall and social desirability bias. Consequently, sexual risk behavior may have been underreported in view of privacy protection. There is also limited generalizability of results since only Chinese women were included in the analysis.