High-resolution mapping of reproductive tract infections among women of childbearing age in Bangladesh: a spatial-temporal analysis of the demographic and health survey

Sexual and reproductive health and rights, currently featured on the Sustainable Development Goal agenda, are fundamental for sustainable development [1, 2]. Female reproductive tract infections (RTIs), playing an important role on reproductive health, become a major public health concern, particularly in developing countries where they are endemic [3]. Women RTIs refer to endogenous, iatrogenic or sexually transmitted infections affecting the reproductive tract of women. They usually originate in the lower reproductive tract (e.g., vaginitis or cervicitis) and may produce symptoms such as abnormal vaginal discharge, genital pain, itching and burning feeling with urination [4‐6]. Women of childbearing age, generally referring to women aged 15–49 years old, are the most susceptible group to RTIs, as they are in child-bearing period and have frequent sexual life [7, 8]. In developing countries, RTIs become major but silent public health problems devastating women’s lives. More than 1 million women and infants die of the complications (e.g., postabortal and puerperal sepsis, ectopic pregnancy, fetal and perinatal death, and infertility) resulted from RTIs each year [9]. Besides, untreated infections increase the risk of other diseases, such as acquiring and transmitting human immunodeficiency virus (HIV) infection, chronic lower abdominal pain, emotional distress social rejection of women and cervical cancer [10].

Bangladesh, classified as the Least Developed Countries by United Nations, has high risk of poor female reproductive health [11], although the Government of Bangladesh has pursued a number of strategies, such as the Urban Primary Health Care Project, seeking to provide services to women of victims of violence and to respond to the reproductive [12] and Initiation of Family Planning Programme [13]. To our knowledge, there is no nationwide report on RTIs in Bangladesh currently, but related data from different surveys suggest a worrying situation. A survey in the capital city Dhaka, found the prevalence of bacterial vaginosis and candida reached 23.3 and 32.5%, respectively, based on 2579 randomly selected married women [14]. In high-risk groups such as sex workers, up to 67.4% of women have cervical and/or vaginal infection [15]. The prevalence of female RTIs varies across the country, thus understanding the spatial-temporal distribution of RTIs and the corresponding influencing factors will be of crucial importance for guiding intervention strategies in limited resource settings.

Risk maps have been widely used in epidemiological studies for describing disease risk distribution [16‐18]. Bayesian geostatistical modeling is one of the most rigorous inferential approaches for reliable risk estimates. It explores the association of survey data with potential influencing factors, employs spatial-specific random effects accounting for other unknown or unobtainable factors, and estimates the disease risk at areas without observed data [19]. In other words, it estimates disease risk (dependent variable) at areas without observed disease data (e.g., areas lack of surveillance or areas un-sampled in surveys), based on known potential influencing predictors (independent variable) at the corresponding areas and the spatial correlations between areas with disease survey data and that without. High spatial resolution maps track the geospatially pattern of disease risk, underscore high risk areas [20], and help health workers and policy makers to precisely identify priority areas where effective interventions should be targeted. In resource-limited countries, such maps are especially meaningful for allocation of limited medical resources to where most needed in a cost-effective manner.

In this study, we aimed to apply geostatistical models to estimate the spatial-temporal distribution of RTIs at high spatial resolution in Bangladesh, based on both the survey data from Demographic and Health Survey (DHS) Programs in the years 2007, 2011 and 2014, and other datasets with environmental, climatic and socioeconomic information, providing policy makers with disease distribution data for this period, in order to inform interventions, and to provide a basis for future RTI research.

In this study, our goal is to better understand the problem of female RTIs in underdeveloped countries like Bangladesh and to inform pre-emptive and precise interventions. Through Bayesian spatiotemporal models, we have created high precision maps for 2007, 2011, and 2014. One advantage of our spatial-temporal model is that it is able to cope with the changing locations and quantity of sampled clusters in each of the surveys [37]. Moreover, spatial-temporal model fits all survey data in a single model, allowing more data to be utilized to improve the statistical efficiency.

Women in low- and middle-income countries (LMICs) tend not to seek health care unless they are suffering alarming RTI symptoms [9]. Lack of awareness and attention to RTIs has led to more serious consequences. For instance, one-third of preterm births are attributed to reproductive tract infections during pregnancy, which often go undetected and untreated in LMICs [38]. Large-scale implementation of effective interventions, such as screening and treatment cost waivers, is often difficult to achieve, especially in countries with limited resources. Therefore, it is very cost-effective to find the small geographical priority areas according to the high-precision map for intervention. We produced the first model-based, high-resolution risk maps of RTIs in the country, based on three national cross-sectional survey data of Bangladesh DHS. RTI risk maps at district- and division-levels were further summarized and presented, which are important for policy makers at different levels of administrative divisions.

Our population-adjusted estimates show that in Bangladesh, there were approximate 11.1% (95% BCI: 10.5–11.7%), 13.9% (95% BCI: 13.3–14.5%) and 13.4% (95% BCI: 12.8–14.0%) of women of childbearing age reported reproductive tract infections in 2007, 2011 and 2014, respectively. This risk may be underestimated, as definition of RTIs in our study is based on self-reported symptoms of having abnormal genital discharge or genital sore/ulcer, which are major indicators suggesting RTIs, rather than hospital confirmed diagnoses. The asymptomatic cases of RTIs are ignored [39]. On the other hand, women reported having abnormal genital discharge or genital sore/ulcer can be generally considered as in a more severe situation of RTIs than those with asymptomatic infections, thus our estimates reflect the cases with more serious RTIs that need to pay more attention to.

The high-resolution risk maps of RTIs not only identify priority areas but also show spatial details of temporal changes across survey years that assist spatial targeted intervention. The southern coastal areas, the western Rajshahi Division, the middle of Khulna Division in the western part of the country, and the southwestern Chittagong Division were estimated to be very high-risk areas (> 20%) in 2014 that urge attention. Most areas in the country show obvious increase of prevalence from 2007 to 2014, particularly, the junction of the three districts (Naogaon, Nawabganj, Rajshahi) in the northwestern Bangladesh, where special focus show be put. In addition, proper health resources are suggested to allocate preferentially not only to areas with high RTI risk but also to areas with large number of infected cases, such as high-population-density areas in the capital city Dhaka and the second largest city Chittagong.

A negative relationship was found between the risk of RTIs and the household wealth, which is consistent with previous studies [40‐43]. This result supports the high RTI risk in the coastal areas of southern Bangladesh, which are among the poorest in the country. The income level may influence women’s health behaviors thus impact the transmission of pathogens. A study shows that women with high income were more likely to use contraceptives than those with low income [44]. In addition, women in the poor families were intend to have high-risk behaviors, such as earlier childbearing [45], earlier sexual debut [46, 47], and transactional sex [48]. We also identified a negative association for RTI risk with elevation and a positive one with distance to the nearest fresh water body. To our knowledge, there are no literatures ever reveal direct relationships of the above environmental factors with RTIs. However, these factors may influence the behaviors and socioeconomic status of people [49], thus show significant association with RTIs.

To obtain more accurate estimates of RTI risk, we made full use of available data from multiple sources, such as DHS, MODIS/Terra, WorldClim, SEDAC, SWBD and WorldPop (Table S1, Additional file 1). However, other potential influencing factors, such as social attitudes [50] and the number of sexual partners [51, 52], are not available at sub-national level, thus cannot be included in our analyses. In addition, as we did not obtain data at high spatial resolution for wealth of household, we used district-level data for risk prediction, by assuming levels of wealth within districts were similar, which may lead to spatial misalignment issue and result in bias. For WorldClim and SEDAC data, the data periods are before 2000 and corresponding updated data are unavailable, thus temporal misalignment may exist.

Nevertheless, our final model had reasonable predictive ability, as model validation suggests that it was able to correctly estimate 74.49% of locations within a 95% BCI coverage. However, the mean error, slightly larger than zero, may suggest a mild underestimate of the model. Considering omitted variable-bias (OVB) issue that results from the elimination of important variables a process where only one of the two highly correlated continuous variables is retained, we went back to the results and found that during this process, only one variable (i.e., education years of husbands) was dropped due to its highly correlated (with correlation coefficient 0.92) with the variable “education years of women”. From a professional point of view, the education of women themselves may influence the RTI more directly than that of their husbands, thus omitting this variable may cause little OVB.

Due to the unavailability of the newest Bangladesh DHS data in 2017, we analyzed the data from 2007 to 2014, which may not fully reflect the most recent situation. Nevertheless, most areas in Bangladesh show obvious increase of RTI risk from 2007 to 2011, then became stable between 2011 and 2014. The Bangladesh government has published a set of policies and strategies to improve women’s health since 2009, such as the National Adolescent Reproductive Health Strategy (2009), the National Education Policy (2010), the National Maternal Health Strategy (2011), the National Women’s Development Policy (2011) and the National Plan of Action on Adolescent Sexual and Reproductive Health (2013) [13]. These efforts may have certain effects on control of RTIs, as the infection risk in most areas of Bangladesh maintained stable instead of increase between 2011 and 2014. However, long-term evaluation is needed. Our analyses should be updated as soon as the 2017 DHS data is released. One the other hand, more efficient control interventions should be carried out in priority areas, which may include health education and hygiene, screening and empowering women. Effective health and personal hygiene education is thought an important measure for women RTI control, by improve women’s knowledge of RTIs, enhancing the awareness of the disease prevention and enabling them maintaining good life style [53]. Screening is another powerful method to detect asymptomatic infected women as early as possible [54]. Furthermore, other strategies such as empowering women, providing educational and employment opportunities for women and improving basic health care services, are advocated by WHO as essential practice for control of RTIs [55]. One successful example is the case in Daqing City of China, after a series of actions (e.g., reproductive health knowledge promotion, health file establishment and tracking), the prevalence of RTIs decreased significantly [56].

In conclusion, we present the first model-based spatial-temporal risk estimates of RTIs at 5 × 5 km resolution in Bangladesh, which can aid control strategies targeted to priority areas cost-effectively. Our results show that more than one eighth of women of childbearing age reported symptoms suggesting RTIs in Bangladesh, urging the government to pay more attention to the worrying situation of female RTIs in the country.