Social, Economic and Ecological Drivers of Tuberculosis Disparities in Bangladesh: Implications for Health Equity and Sustainable Development Policy

Abstract

Tuberculosis (TB) remains a leading cause of death in Bangladesh, disproportionately affecting low socio-economic status (SES) populations. This review, guided by the WHO Social Determinants of Health framework and Rockefeller-Lancet Planetary Health Report, examined how social, economic, and ecological factors link SES to TB burden. The first literature search identified 28 articles focused on SES-TB relationships in Bangladesh. A second search through snowballing and conceptual mapping yielded 55 more papers of diverse source types and disciplines. Low-SES groups face elevated TB risk due to smoking, biomass fuel use, malnutrition, limited education, stigma, financial barriers, and hazardous housing or workplaces. These factors delay care-seeking, worsen outcomes, and fuel transmission, especially among women. High-SES groups more often face comorbidities like diabetes, which increase TB risk. Broader contextual drivers include urbanisation, weak labour protections, cultural norms, and poor governance. Recommendations include housing and labour reform, gender parity in education, and integrating private providers into TB programmes. These align with the WHO End TB Strategy, UN SDGs and Planetary Health Quadruple Aims, which expand the traditional Triple Aim for health system design by integrating environmental sustainability alongside improved patient outcomes, population health, and cost efficiency. Future research should explore trust in frontline workers, reasons for consulting informal carers, links between makeshift housing and TB, and integrating ecological determinants into existing frameworks.

1. Introduction

Tuberculosis (TB) remains one of the leading causes of death in Bangladesh [1], one of the WHO’s high TB burden countries [2]. This is despite the adoption of the WHO’s Directly Observed Therapy, Short-course (DOTS) by the National Tuberculosis Programme (NTP) in 1993 [3], the mainstay of which is case detection via sputum tests and treatment with a 6 month course of antibiotics [4]. As a ‘social disease’, the TB burden is modulated by social determinants of health (SDHs)—wealth, education, occupation and housing [5]—and ecological determinants of health (EDHs)—air quality, resource scarcity and land use [6]. Since SDHs and EDHs are themselves interlinked, this paper refers to these determinants collectively as social and ecological determinants of health (SEDHs), which in turn form a composite socio-economic status (SES) [7]. Furthermore, this paper refers to populations experiencing relative disadvantages in one or more of these domains compared to the broader population as ‘low-SES’.

This review aimed to identify drivers and the more proximal mechanisms that contribute to TB inequities in Bangladesh. This process was guided by the WHO SDH Framework (Figure 1) and the Rockefeller-Lancet Commission Report on Planetary Health [6], both of which were sources of SEDHs to utilise as keywords in the initial literature search. The WHO SDH Framework also conceptualised intermediary determinants of health (IDHs) as the proximal mechanisms through which structural and contextual factors influenced specific health outcomes—in this case, the socio-economic distribution of the tuberculosis burden. This analytical lens was complemented by incorporation of planetary health principles. Planetary health emphasises the role of flourishing natural systems on human health, a concept which guided our review in the following key ways: conducting an interdisciplinary approach to literature and evidence searching [8]; an additional focus on EDHs for the TB burden [6]; and informing actionable interventions that facilitate progress towards the Sustainable Development Goals (SDGs) [9], WHO End TB Strategy [10], and Quadruple Aims towards planetary healthcare systems [11]. The Quadruple Aims augments the existing triple aims framework for designing healthcare systems. It incorporates planetary health principles—safeguarding environmental and ecological wellbeing—while also furthering progress towards the three original aims: reducing costs, enhancing the patient experience, and improving care-team wellbeing. This expanded framework recognises that human health is inseparable from the health of natural systems [11]. This review primarily tailors its policy recommendations to align with the pathways on how health system reforms in Bangladesh can simultaneously improve TB outcomes, enhance social equity, and minimise ecological harm.

In Bangladesh, low-SES populations remained disproportionately burdened by TB, contracting it at a rate five times greater than the highest SES group. Those with no educational qualifications exhibited a TB prevalence rate of 138.6/100,000 as opposed to 39.3/100,000 for those with over 10 years of education. Elementary occupations—agricultural workers or manual labourers—also exhibited higher prevalence of TB at 107.3/100,000 and 187.0/100,000, respectively [12]. In regression analysis, individuals with a monthly income above 25,000 Taka (BDT) were 71% less likely to contract TB, demonstrating a significant negative association between income and TB prevalence [13]. TB is also pervasive in low-income housing types, such as Dhaka slums where prevalence is four times higher than the city average [14] and predominantly rural clay-made houses [15]. Furthermore, these populations exhibit lower case notification and less readily access DOTS despite it being free of charge [12], potentiating the existence of barriers to diagnosis and treatment. Controlling TB also has broader implications for Bangladesh’s national development [16], the rise in drug-resistant disease [17], and the resilience of its health system [18].

The persistent disparity in the TB burden between SES populations as well as its overwhelming public health burden in Bangladesh justified an in-depth analysis of the disease’s interlinked social, economic, and ecological drivers. Over the past decade, no review has been identified that utilises the SDH framework or planetary health principles to synthesise a diverse body of evidence on social, economic, and ecological mechanisms that shape TB disparities in Bangladesh, particularly with the aim of informing sustainable policy recommendations.

Objectives

• To identify the social, economic, and ecological determinants contributing to the disproportionate burden of tuberculosis among low-SES populations in Bangladesh.
• To examine proximal mechanisms through which these determinants influence the TB burden.
• To generate sustainable policy recommendations aligned with the Sustainable Development Goals, WHO End TB Strategy, and Quadruple Aims towards Planetary Health Systems.

2. Methods

This paper employs a narrative review methodology to examine the mechanisms by which SEDHs influence the TB burden in Bangladesh. This paper aims to achieve a comprehensive and interdisciplinary appraisal of the literature, rather than through a narrow or exclusive criteria. Therefore, a flexible narrative review process is justified to avoid unintentional exclusion of relevant literature.

Two literature searches were conducted. The initial literature search inputted TB alongside SDHs from the WHO SDH Framework—income, education, occupation and housing—and EDHs from the Rockefeller-Lancet Commission Report [6] into PubMed, ProQuest, Web of Science and Scopus (

Table 1. Keywords for SEDHs in initial literature search.

Conceptual Framework Derived From	SEDH	Keywords
SDH Framework [7]	Wealth	Wealth OR salary OR pay OR wages OR earnings OR income
SDH Framework	Educational Attainment	Education OR schooling OR literacy OR graduate
Planetary Health EDHs [6]; SDH Framework	Housing, Land Use	Homelessness OR home ownership OR slum OR Kutcha OR Pucca OR poor-quality housing OR mud hut OR overcrowding OR urbanisation
SDH Framework	Occupation	Employment OR workplace hazard OR occupational hazard OR overcrowding
Planetary Health EDHs	Air quality	Pollution OR smoking OR dampness OR ventilation

). This search was restricted to peer-reviewed journal articles specifically analysing a potential relationship between an SEDHs and TB in Bangladesh nationally or within specific regions. Papers of varying methodologies—case–control, cross-sectional, or qualitative—were included. Preference was given to literature published after 1 January 2010 to achieve an up-to-date understanding of TB as Bangladesh has experienced significant national development and associated shifts in disease patterns in recent decades. However, earlier sources were included when they offered relevant contextual insights or represented the most recent available data. Papers fulfilling the above criteria were compiled and quality assessed in a pragmatic manner utilising principles drawn from the Critical Appraisal Skills Programme (CASP) checklist.

A second literature search was then conducted utilising keywords informed by themes and concepts derived from the initial cohort of articles. This stage broadened the scope of the review to include studies that provided insight into the mechanisms identified from the first literature search. Notably, these articles may not have been explicitly related to TB or Bangladesh and from disciplines other than public health and epidemiology—engineering, nutrition, gender studies, behavioural science, and more. Source types were also expanded to include conference papers, dissertations, working papers and grey literature. This process facilitated a more granular understanding of the dynamics influencing the TB burden. Grey literature was incorporated to contextualise findings; in particular, national survey data was utilised to estimate the scale of a given SEDHs’ influence on the TB burden. These sources were identified through snowballing and targeted web searches and included documents from institutions such as the Bangladesh Bureau of Statistics (BBS), the World Health Organization (WHO), and the Bangladesh Demographic and Health Survey (DHS). Snowballing was used to identify additional sources cited in relevant literature (Figure 2).

3. Results

The initial literature search yielded 28 peer-reviewed journal articles. A total of 12 of these studies employed cross-sectional methods, 6 case–control, and 10 longitudinal or other. Snowballing and a second search incorporating concepts from these studies identified 55 further articles, contributing to the identification of IDHs. Nine articles from the second literature search were published prior to 2010 and were included due to their provision of the most recent available data or analysis. Additionally, there were 21 sources of grey literature. This literature appraisal identified five IDHs through which SEDHs influence tuberculosis burden (

Table 2. IDHs contributing to the TB burden in Bangladesh.

IDH	Description
Section 3.1 Distribution of TB Risk Factors by SES	Low-SES populations have higher prevalence of smoking, child malnutrition, biomass fuel use while high-SES populations exhibit a higher Diabetes prevalence.
Section 3.2 Educational Attainment, Stigma, and Barriers to Case Notification	Low educational attainment contributes to stigma and poor disease knowledge, leading to delayed diagnosis and concealment.
Section 3.3 Financial Barriers to Treatment	Direct and indirect costs create obstacles from diagnosis to completion of treatment, creating a perpetual cycle of management delay.
Section 3.4 Housing Characteristics	Overcrowded, poorly ventilated, low-quality housing increases transmission risk compounded by risk factors in Section 3.1.
Section 3.5 Occupational Exposure	Predominantly low-income agricultural, elementary, and healthcare workers have increased TB risk.

).

3.1. Distribution of TB Risk Factors by SES

Susceptibility to TB is influenced by both environmental risk factors—poor air quality from smoking [19] and cooking with biomass fuels (plant materials or dried cow dung) [20]—and medical ones—diabetes [21] and malnutrition [22]—as shown in Figure 3. As discussed below, these risk factors are themselves closely linked with SES, representing an IDH through which it influences the TB burden.

Determinants of air quality are closely linked with low educational attainment and wealth. Smoking is negatively associated with educational attainment [23] and more prevalent amongst low-income quartiles [24]. This association is compounded in urban slums, where a higher smoking rate, 35% [25], and overcrowding amplifies the TB susceptibility and transmission risk [14]. Passive or second-hand smoking also increased the risk of TB contraction by 1.70-fold [26]. Thus, smoking serves as a pathway through which lower wealth and education levels contribute to TB burden, both directly and by compounding transmission risks in densely populated slum environments. Similarly, the use of biomass fuels for cooking—such as cow dung or plants [27], which increase the risk of extra-pulmonary TB by seven-fold [20] and pulmonary TB by 3.50-fold [27], and are more prevalent among low-income populations especially in rural communities as their use is primarily driven by resource scarcity and cost constraints [28]. This suggests that being from a low-SES background may drive reliance on cooking methods that increase TB risk. However, entrenched cultural norms as well as a lack of awareness around the dangers of biomass fuel cooking also contributed to its continued use [29].

Figure 3. Prevalence of TB risk factors by education and income level [23,29,30,31].

Figure 3. Prevalence of TB risk factors by education and income level [23,29,30,31].

The relationship between SEDHs and medical risk factors is more multidirectional. In Bangladesh, child malnourishment is closely associated with low-income households and limited maternal educational attainment [32,33]. As malnutrition both increases susceptibility to TB [22] and complicates treatment [34], it likely contributes to the disproportionate TB burden among low-SES populations. However, diabetes, another risk factor for tuberculosis [21], is more prevalent in middle and high-income populations though still less prevalent among those with post-secondary education relative to those lacking formal education [30]. This may be attributed to the more sedentary lifestyle and higher calorie intake among high-wealth populations [35].

These risk factors may contribute to TB susceptibility among high-SES populations, partially counterbalancing the burden of ecological factors and their associated TB risks on low-SES populations. However, while TB risk factors exist across SES populations, a larger proportion of TB cases in Bangladesh are linked to smoking and malnutrition [36]—both disproportionately prevalent in low-SES populations. That said, this difference falls within the margin of error [36], highlighting the need for further research to determine the relative strength of each risk factor.

3.2. Educational Attainment, Stigma and Barriers to Case Notification

Low educational attainment, particularly below the secondary school level, is associated with a heightened risk of TB in Bangladesh, largely through its influence on social stigma and misconceptions surrounding TB as a disease. Stigma has been widely reported among individuals with limited formal education in both rural villages surrounding Rajshahi [37] and urban slums in Dhaka [38,39]. Among the drivers of such stigma was the belief that TB was a divine punishment for moral transgressions, leading to blame and social exclusion for affected individuals [37]. Stigma was also disproportionately felt by women, some of whom feared damaged marriage prospects or being excluded from their home as a result of a TB diagnosis, prompting many to conceal their symptoms [40]. Conversely, individuals with a higher educational attainment and domicile in urban areas were more likely to exhibit greater awareness of TB in the domains of symptoms, mode of transmission and available treatment services [41].

Insufficient knowledge of TB domains, in turn, impacts treatment seeking and adherence while stigma may discourage such behaviours in the community more broadly (Figure 4). In rural Bangladesh, educational attainment was associated with a greater likelihood of referral to TB treatment services within an acceptable timeframe of 45.6 days [42] and compliance with the TB treatment course among those with multidrug-resistant TB (MDR-TB) [43], likely facilitated by better understanding of the disease [41]. In addition, parental education was also associated with uptake of the BCG vaccine in newborns, which is protective against TB [44]. In contrast, stigma towards TB patients and poor understanding of the disease impedes presentation to and adherence to TB treatment [38] by those with lower educational attainment. Furthermore, the gendered nature of stigma poses an additional barrier to TB diagnosis and treatment access. Sputum smear microscopy—the mainstay of TB diagnosis under DOTS [3]—may be underutilised by women, for whom coughing up sputum is particularly stigmatised [45]. While tuberculosis mortality is higher in men than women [46], women exhibit lower referral rates to tuberculosis diagnostic services with a ratio of female to male patients of 0.81 in outpatient services and 0.52 in sputum testing [47,48], which this stigma has possibly contributed to.

Lower levels of education are linked to widespread misconceptions about TB and heightened stigma towards TB patients, particularly women, both of which can delay treatment-seeking in the community and reduce adherence to prescribed regimens. These factors contribute to the disproportionate TB burden among low-SES populations, specifically those with limited formal education.

3.3. Direct and Indirect Financial Barriers to TB Treatment

Low income or limited wealth exacerbates the tuberculosis burden among low-SES populations by imposing financial barriers to diagnosis and treatment—even among those who overcome initial deterrents to care-seeking and are willing to access services. Although the DOTS programme is officially free of charge to patients [49], both direct and indirect costs continue to disrupt treatment access. Direct costs refer to out-of-pocket expenses imposed by healthcare providers, particularly private providers and informal practitioners (IPs). Indirect costs encompass non-medical expenditures such as transportation and informal payments, which are often required to navigate the healthcare system. Together, these financial burdens create a self-reinforcing cycle in which predominantly indirect cost-related obstacles delay diagnosis and treatment, encouraging utilisation of poorer quality care providers (Figure 5).

Private providers and IPs often complicate referral to DOTS facilities and impose a direct financial burden on low-SES patients. A significant minority, 39%, of TB patients initially presented to private facilities, where HCWs were less likely to have received training on treating TB patients and follow NTP guidelines on diagnostic procedures [50]. Consequently, patients often had to make multiple visits before receiving a diagnosis and were frequently misdiagnosed [50]. Additionally, charges associated both with the use of private facilities and transport to these facilities [50], representing direct and indirect costs, respectively, make the process disruptive and costly for low-SES populations. Despite these challenges, private facilities were utilised by patients regardless of income or area of residence [51]. Further research into the drivers of private, as opposed to public, healthcare utilisation among of low-SES TB patients is warranted given their cost and inefficiencies.

IPs—untrained or semi-qualified providers—who often serve as the first point of presentation for low-SES, rural populations [52] play a similarly disruptive role. Notably, patients who initially presented to IPs experienced shorter delays in accessing care than those who first consulted qualified practitioners (30% vs. 68%), suggesting greater initial responsiveness [53]. Despite this, these practitioners rarely adhered to NTP guidelines, being less likely to administer sputum smear microscopy tests or issue referrals for treatment [53,54], ultimately delaying treatment and increasing the risk of disease progression for their disproportionately low-SES patients. Furthermore, financial expenditures incurred prior to DOTS enrolment through IPs and aforementioned private providers contribute to a higher prevalence of catastrophic health expenditures (CHEs)—out-of-pocket payments exceeding 10% of total household expenditure—among the poorest quintile [55].

However, even once enrolled on ostensibly free DOTS programmes, indirect costs complicate treatment compounding the obstacles faced by low-SES populations. Transport and foregone wages associated with excessive time off work due to long wait times [56], are especially pronounced during the 6 to 12 month TB treatment regimen [3]. The associated transport and time off work may be especially burdensome for patients from lower occupational classes, such as elementary or agricultural workers [57]. In addition, instances of corruption and informal payments intended to secure preferential care have been reported in public hospitals [58]. These practices are exacerbated by resource constraints, such as the unavailability of beds and insufficient drug supply [59] and may disadvantage low-SES patients, who are often less able to afford such unofficial costs and may therefore receive lower priority in treatment. These factors have likely contributed to the paradoxical finding that public facilities are associated with higher costs for patients than private ones [56] and explain the association between low income with long waiting times, insufficient drug supply and a lack of treatment facility at public hospitals [59]. These features may additionally drive patients towards the aforementioned private and IPs creating a cycle of treatment barriers summarised in Figure 5. These challenges are consistent with the finding that low-income is associated with patients not following up with treatment [60].

3.4. TB-Prone Characteristics of Low-SES Housing

The burden of TB on low-SES populations, particularly children, is compounded by poor quality housing structures that exhibit overcrowding [5], poor ventilation and air quality [61]. In logistic regression analysis, children sleeping in a room with two or fewer inhabitants were three times less likely to contract TB [62] while those sleeping in a room with over four inhabitants were 2.64 times more likely to contract it [63]. In-house overcrowding was also independently associated with a 2.90-fold increase in child hospital admissions for acute respiratory infections [64]. This was consistent with overcrowding being a risk factor for TB in low and middle-income countries (LMICs) across the world [61]. Furthermore, across LMICs, those living in makeshift houses exhibited a threefold increase in TB risk relative to those in brick homes [61] while slum dwellers were almost five times more likely to develop TB relative to the national average [65]. These phenomena have implications for urban health and rural domiciles and, themselves, have several financial and social drivers (Figure 6).

Overcrowding is a key feature of urban slums, which had an average of four to five people per 100 square feet [66]. Due to ongoing rural-to-urban migration [67] and a growing housing deficit [68], overcrowding in urban slums has likely persisted or worsened [69]. As such, TB prevalence was twice as high in these domiciles as the national average [14]. Overcrowding is likewise present in rural ‘kutchas’ [64], a colloquial term for non-permanent structures made of mud, bamboo, grass or other materials aside from brick or cement [70]. Overcrowding in rural housing can be attributed to the manner of construction, whereby cost constraints drive construction of single-room houses, leading to a crowded sleeping space, which facilitates TB transmission in children [62]. Therefore, cost-driven, TB-prone building practices compound overcrowding, which ultimately increases the TB burden among low-SES slum [14] and kutcha dwellers [15].

Poor ventilation and air quality represent another mechanism through which slum and kutcha housing facilitate TB transmission. Poor indoor air quality was associated with a 1.68-fold increase in contracting TB [71]. Both kutcha houses [72] and Dhaka slum dwellings [73] exhibit poor air quality and ventilation, with higher air pollutants recorded in these housing types relative to others [72]. In rural domiciles, this can be partly attributed to poor-quality building materials [72]. The vast majority of kutchas (98.7%) were self-constructed [70] and choice of building materials—typically mud over brick—was mostly driven by cost constraints [74]. This likely led to the construction of homes of poor-quality materials that reduce household ventilation and therefore compound the spread of tuberculosis. For example, in Rajshahi, a majority of pulmonary tuberculosis patients lived in kutcha houses with poor ventilation [15]. Therefore, this phenomenon, compounded by the relative high prevalence of smoking [23,24] and biomass fuel cooking [28] in poorer domiciles, significantly contributes to the TB burden among low-SES populations. Cost constraints are likely still driving rural Bangladeshis towards TB-prone home building practices given that a majority of residential units were still classified as kutcha [75]. However, more up-to-date research on the drivers of poor construction quality, particularly in rural domiciles, is warranted.

The high prevalence of kutcha housing [75] and urban slums [76] as residential units underscores the significant role of inadequate housing in driving TB disparities among low-SES populations through the amplification of poor air quality and deterioration of urban health.

3.5. Occupational Exposure Among Elementary and Agricultural Workers

Tuberculosis can be transmitted zoonotically from cattle via the M. bovis strain [77], increasing the risk of infection for agricultural workers. In some regions, cattle handlers—especially those with low educational attainment or monthly incomes below 10,000 Taka ($88.50)—exhibited inadequate knowledge of zoonotic transmission [78]. The prevalence of M. bovis in livestock was 45.6% in these areas [79], yet NTP guidelines include no provisions for controlling M. bovis in animal populations [3]. This is consistent with, and a potential contributor to, findings that agricultural workers exhibit a greater risk of TB contraction [12].

Garment workers who were targeted by NGOs aiming to deliver TB care in Dhaka [80] are similarly exposed to TB relative to other occupations. Consistent with the associations above, educational attainment was significantly associated with TB knowledge among these workers [81]. Given that educational attainment was relatively low among garment workers [81], this likely impedes treatment seeking in the manner outlined in Figure 4. This suggested that an increased occupational risk falls on this low-income population, exacerbated by factory overcrowding [82]. This is consistent with survey findings that unreported TB diagnoses are more likely to be from those who lacked either any or secondary education [12].

HCWs also face a heightened risk of TB infection, with risk increasing with each year employed as an HCW on TB wards [18]. Limited resources and space impeded patient isolation and infection control measures [83], likely reflecting shortcomings in implementing international infection prevention and control (IPC) guidelines [84]. HCWs are socio-economically diverse, making it challenging to determine whether the phenomenon of hospital-associated tuberculosis infections disproportionately falls on low-income populations. There was no apparent relationship between infection control capacity and the regional poverty rates of hospitals [85,86]. However, one indicator is that frontline HCWs, colloquially referred to as Shasthya Sebikas (SS), were found to have a heightened risk of contracting the disease [87]. These workers are often local women, who may be driven into the career by financial need [88]. As a result, the increased burden of tuberculosis on HCWs possibly falls on those from low-income backgrounds.

4. Discussion

This review explores the five IDHs that modulate TB burden in Bangladesh and represent the overlapping influence of SEDHs. These represent a comprehensive account of the link between low-SES and higher TB burden, corroborating, summarising and synthesising the existing literature base. These mechanisms demonstrate that low-SES populations are disproportionately affected by TB across the care continuum—from infection susceptibility to treatment adherence—a pattern largely consistent with findings reported in other high TB-burden and LMIC settings (Figure 7).

The prevalence of TB risk factors, housing characteristics and construction techniques and occupational exposure represent the higher TB susceptibility among low-SES populations. Low-SES populations exhibit the highest prevalence of TB risk factors, such as smoking [23], child malnutrition [31] and cooking with biomass fuels [28] (Figure 3). Maternal education was significantly associated with avoidance of child malnutrition the Ivory Coast [89] and its promotion has reduced TB prevalence in Nigeria [90]. Low quality and cost constraint driven construction [72,74] likely facilitates TB transmission in low-income housing due to overcrowding [5] and poor air quality and ventilation [61], the latter of which may be exacerbated by environmental risk factors [23,31] (Figure 6). TB transmission was also heightened in rural, kutcha housing relative to other domiciles in India and Pakistan [61], reinforcing the link between overcrowding and poor air quality with TB incidence. Elementary [80] and agricultural occupations [78], which report the lowest monthly earnings in Bangladesh [57], as well as HCWs [18] are at a high risk of occupational TB exposure. The risk of zoonotic transmission of TB among agricultural and livestock workers was also present internationally, warranting guidelines to improve case notification and adherence [91]. Furthermore, in other LMICs, HCWs are placed at an increased risk of TB contraction, in part, due to insufficient implementation of IPC guidelines [92], which is likewise lacking in Bangladesh [84].

Stigma and insufficient disease knowledge and financial barriers, rooted in low educational attainment and wealth, manifest as obstacles to diagnosis and treatment. Low educational attainment engenders both stigma towards TB patients [37], particularly women [40], and insufficient knowledge of the disease, prompting many to conceal their diagnosis or not seek treatment [41]. This was consistent with perceived stigma being a predictor of adherence to DOTS therapy in West Bengal, India [93]. Furthermore, from initial presentation, there are financial barriers to successful completion of DOTS through superficially accessible but costly private providers and IPs [50,53], inefficiencies in public facilities necessitating financial bribes for treatment [58] and excessive time off work and transport costs necessitated by the lengthy treatment course [56]. IPs likewise form a significant component of healthcare systems in other developing countries across Sub-Saharan Africa and Asia due to their relative accessibility but typically exhibit poor adherence to NTP guidelines and low referral rates [94]. However, Bangladesh is unique in its high proportion of TB patients initially presenting to private providers relative to other high TB-burden countries [95]. Furthermore, the finding that total patient costs were higher at public rather than private providers [56] is different to other LMICs, such as Vietnam [96], and potentially drives the presentation to IPs and private facilities.

A notable caveat to this relationship is the relative high prevalence of diabetes [30], a risk factor for TB [21], among high-SES populations. This is consistent with the Epidemiological Transition Theory, whereby economic and social development give rise to a greater chronic, non-communicable disease burden while reducing the presence of acute, mostly communicable diseases [97], such as TB. Since Bangladesh is still progressing through this transition with a dual burden of communicable and non-communicable disease [16], in the interim, the rise in diabetes in educated demographics has increased tuberculosis susceptibility as well. Although these factors partially attenuate this relationship, they do not negate the overwhelming evidence that TB disproportionately affects lower-SES populations.

4.1. Contextualising Results Within the WHO SDH Framework

The mechanisms identified in this review correspond to IDHs of the WHO SDH Framework, as they are the most proximal factors influencing health equity and represent the intersection of structural determinants and contextual influences (Figure 1). Contextual factors—including macroeconomic policies, governance, social policies, public policies, and cultural and societal values—shape IDHs (Figure 8) and, consequently, inform potential interventions to address the inequitable burden of TB in Bangladesh.

Macroeconomic policies in Bangladesh have contributed to urban-biassed economic growth, prompting large-scale rural-to-urban migration in search of employment opportunities [98]. However, the dearth of urban housing supply [99], exacerbated by insufficient government intervention [100], has likely facilitated the movement of people into overcrowded urban slums, which exhibit a higher TB transmission rate [14]. This is consistent with the land use EDH, whereby natural land has been urbanised for housing and industrial use [6], compounding the deterioration of urban health. Labour laws, another domain of social policies, have inadequately protected workers consistent with Bangladesh being recognised as having some of the weakest labour protections globally [101]. This lack of regulatory enforcement for elementary workers has likely contributed to workplace overcrowding [82] and occupational exposure to TB among garment workers [81,82].

Public policies relating to healthcare have further intensified financial and systemic barriers for low-SES populations seeking TB care. As discussed, private providers and IPs often represent an initial point of presentation for low-SES TB patients [50]. However, there is currently a lack of integration between private and public health providers in Bangladesh, which impedes case notification and subsequently DOTS enrolment [51], potentially contributing to lower case notification among low-SES populations [12] and the cycle of treatment barriers (Figure 5). In addition, limited availability of smoking cessation [102] and child nutrition counselling [103], may have exacerbated the high rate of smoking and child malnutrition among low-SES populations [23] (Figure 3).

Hospital-level governance deficiencies have further compounded healthcare accessibility challenges for low-SES populations [56]. Staff absenteeism, particularly among senior physicians, was common due to their preference for more lucrative private practice. In addition, some staff were found to improperly charge patients for prescriptions, diagnostic tests or referrals [104]. Staff shortages in rural hospitals, exacerbated by healthcare professionals’ preference for urban employment [104] as well as the aforementioned resource insufficiencies, have contributed to prolonged waiting times, resources constraints [59] and informal payments. These further limit low-SES patients’ access to timely treatment and contribute to the treatment barrier cycle (Figure 5). Poor governance relating to the development and implementation of IPC measures further increases the risk of occupational exposure. Within public hospitals, the insufficient resources and staff shortages complicate the implementation of international IPC measures [84], increasing the risk of occupational exposure among HCWs. Similarly, despite the prevalence of zoonotic TB transmission in some regions, there are no existing guidelines on this condition [3], potentially underlying high TB transmission and mortality amongst agricultural workers [79].

Finally, cultural and societal values shape the persistence of key TB risk factors, including reliance on biomass fuels, stigmatisation of TB patients, and the prevalence of environmental risk factors. While cost constraints were the primary barrier to adopting cleaner fuels in the place of biomass fuels, their use is an entrenched, normative behaviour, particularly in low-SES, rural populations, that further inhibits the transition to TB-safe cleaner fuels [29]. Likewise, stigma towards TB patients was, in-part, influenced by religious beliefs, particularly that TB was a divine punishment, which further drove a sense of fatalism towards accessing treatment as patients believed their disease progression was outside their control [105]. Lastly, patriarchal norms shaped gender disparities in education [106], in turn, influencing uptake of the BCG vaccine and child malnutrition, both of which are modulated by maternal education [32,44]. While public policies such as the female stipend programmes (FSPs) have driven progress towards gender parity in education [106], intrahousehold investment in education, such as in private tutors, is still biassed towards boys [106]. This attenuates gender parity and contributing to higher secondary school dropout rates for girls [107]. This highlights the role of community values—religious beliefs and patriarchal norms—in shaping patient behaviours throughout the care continuum from protective health behaviours to treatment seeking. Coordinated community engagement to increase TB awareness through religious leaders, television advertisements and school-based interventions, has demonstrated some efficacy in improving case notification and diagnosis [108], suggesting that community leaders can play a role in shaping health outcomes. However, more up-to-date research on this is required.

Therefore, each element of the WHO Framework’s Socioeconomic and Political Context plays a critical role in shaping the five IDHs identified in this review. This underscores multiple potential entry points for targeted interventions aimed at mitigating the TB burden among low-SES populations.

4.2. Recommendations

The mechanisms and contextual influences identified in this review inform several policy recommendations to reduce the tuberculosis burden among low-SES populations in Bangladesh (

Table 3. Recommendations with corresponding relevant stakeholders and alignment with key targets.

Recommendation	Description	Stakeholders	Alignment with Quadruple Aims, SDGs, End TB Pillars	Monitoring Strategy
Streamline Diagnostic and Treatment Availability	Implement SIMPLE TB strategy to improve case detection and treatment initiation	Ministry of Health and Family Welfare; international aid organisations; NGOs	Quadruple Aims 3; End TB Strategy Pillar 1	Case notification and diagnostic referrals
Reduce Household and Workplace Overcrowding	Increase public funding for homebuilding and promote campaigns to strengthen workers’ rights.	National Housing Authority; international development banks	Quadruple Aims 1; SDG 11.1; End TB Strategy Pillar 2	Proportion of houses designated as kutchas or slums in the annual housing survey
Promote Gender Equality in Educational Attainment	Expand upon existing stipends and school-level interventions to improve gender equality in schools	Ministry of Education; Donor agencies (e.g., BRAC)	Quadruple Aims 1 and 2; SDGs 4 and 5; End TB Strategy Pillar 1	Gender parity in secondary education completion and tertiary education enrolment
Facilitate Integration with Private Providers and IPs	Integrate private facilities as well as IPs into DOTS to improve case notification and treatment referral	NTP; Professional medical associations	Quadruple Aims 1; SDG 3; End TB Strategy Pillar 1 and Pillar 2	TB diagnoses confirmed within an acceptable, 45.6 day, timeframe.

). The recommendations outlined above are closely aligned with the Planetary Health Systems Quadruple Aims [11], WHO End TB Strategy [10], and UN SDGs, Goal 3 of which aims to end TB epidemics globally [9]. The Planetary Health Systems Quadruple Aims helped guide the formulation of policies that are sustainable and emphasise preventative or early-stage care, which is more cost-effective and environmentally friendly [11].

4.2.1. Recommendation 1: Streamline Diagnostic and Treatment Availability

Accessing tuberculosis diagnostic and treatment services is still riddled with obstacles for low-SES populations, leading to catastrophic expenditures and delays (Figure 5). In Uganda, a streamlined tuberculosis diagnostic and treatment regimen, known as SIMPLE TB, was implemented, which increased the speed of treatment commencement, particularly in rural communities. However, 10% of TB-positive subjects were still not initiated on treatment under this streamlined regimen [109]. Furthermore, SIMPLE TB’s primary diagnostic tool, Gene Xpert, is more costly relative to current smear tests [110], potentially complicating implementation. That said, the cost per unit reduces with a greater volume of usage [110], necessitating the intervention increasing case notification and diagnostic referrals in order to be financially feasible. Reforming the existing DOTS strategy would require coordination between the Ministry of Health and Family Welfare, international aid organisations, and NGO partners, which is further complicated by a funding gap [111] and poor governance [104]. Frontline health workers, particularly SSs, are also key stakeholders whose buy-in is necessary for practical implementation. That said, if implemented successfully, prompt diagnosis and treatment would theoretically mitigate these obstacles and reduce disparities in tuberculosis diagnosis and poor treatment prognosis for low-SES populations, thereby addressing barriers linked to the income SDH and material circumstances IDH [7]. Due to the catastrophic costs associated with the extended treatment course on low-SES groups [55], this recommendation is the most pertinent and high-impact. This also closely aligns with Pillar 1 of End TB Strategy through promoting early detection and treatment commencement [10]. Lastly, this could reduce the overall environmental footprint of healthcare services through fewer repeat appointments and unnecessary investigations [112], which is a key component of the quadruple aim 3 towards sustainable planetary healthcare systems [11,113]. A key metric for success of this intervention is improved case notification rates as well as reduced regional disparities in case notification.

4.2.2. Recommendation 2: Reduce Household and Workplace Overcrowding

Overcrowding within the household and workplace has led to an increased risk of tuberculosis primarily for low-SES populations. A cornerstone of Bangladesh’s national housing policy has been to alleviate population concentration in large cities and, instead, build up residential infrastructure in small or medium-sized towns [100]. Scaling up this initiative would require collaboration between the National Housing Authority and international development banks. While there have been criticisms of the quality of homes constructed under this initiative [99] warranting the increase in funding, it would likely work to alleviate overcrowding in large urban centres, such as Dhaka, with tuberculosis-prone slum communities. In addition to homebuilding, home improvement campaigns should aim to improve ventilation and air quality in existing housing structures. This targets Goal 11.1 of the SDGs to build affordable housing and upgrade slums [9]. That said, this strategy does not address the underlying causes of rural-to-urban migration, which is primarily seeking better employment opportunities and financial circumstances [98]. This intervention, therefore, targets the WHO social policies contextual element affecting housing [7]. This is linked with the End TB Strategy’s broader Pillar 2 commitment to poverty alleviation and actions on other SEDHs [10]. This is further aligned with promoting urban health, a specific element of Quadruple Aim 1 towards planetary healthcare systems [11]. A primary metric for efficacy for this intervention is a reduction in the proportion of houses designated as kutchas or slums in the annual Survey of on Occupied Residential Houses and Real Estate Services.

4.2.3. Recommendation 3: Promote Gender Equality in Educational Attainment

Bangladesh has made substantial strides towards gender parity in education, with enrolment up until tertiary education reflecting equal educational attainment [107]. However, disparities in tertiary education itself, completion rates for secondary education as well as gender inequities in household education resource distribution persist [106,107]. As mentioned, maternal educational attainment was associated with behaviours that reduce the risk of tuberculosis, such as reducing malnutrition and encouraging BCG vaccine uptake [44,114]. There is further evidence from Nigeria that higher maternal education was correlated with fewer cases of tuberculosis [90]. To further promote female education, government programmes such as the Female Secondary Stipend and Assistance Programme (FSSA) should be expanded, which have yielded greater gender equity in secondary school completion rates in Pakistan and Colombia [115]. The Ministry of Education, donor agencies, and non-profits involved in girls’ education—such as BRAC—are pivotal stakeholders in expanding programmes like the FSSA. This intervention would aim to address the public policy element, particularly that related to education, of contextual factors as well as the health behaviours IDH in the WHO framework [7]. This is linked with Pillar 1 of the End TB Strategy through promoting vaccination against TB [10], SDGs 4 and 5 to provide inclusive education and promote gender equality, respectively [16], and Quadruple Aims 2 to enhance patient education [11]. However, the extent to which financial assistance can counteract entrenched patriarchal attitudes toward female education [116], which form an element of cultural and societal values [7], remains unclear. A metric for the efficacy of this policy is achieving gender parity at higher levels of education, particularly secondary education completion and tertiary education enrolment. Secondarily, an increase in uptake of the BCG vaccine as well as a decrease in child malnourishment in the long-term should be observed.

4.2.4. Recommendation 4: Facilitate Integration with Private Providers and IPs

As discussed, initial presentation to IPs and private hospitals often disrupts timely TB care (Figure 5). Furthermore, these practitioners typically charge for their services [50,55], placing an additional burden on low-SES populations. To mitigate these existing barriers, there should be greater integration of private providers and IPs with DOTS/public healthcare nationally, which have generally reduced the cost per TB patient incurred by service providers [117]. Professional medical associations, informal practitioner networks and national TB programmes are central stakeholders. Donor organisations funding the NTP and regulatory agencies such as the Directorate General of Health Services, must facilitate and monitor integration to ensure compliance with existing protocols. Integration of these services, through establishing referral linkages and versing HCWs in NTP guidelines among other interventions, has been found to increase case notification in regions where it was piloted in Bangladesh [51] and Pakistan [118]. There was a similar observed effect in rural Malawi when IPs were involved in treatment [119]. IPs were trained to recognise TB symptoms, conduct diagnostic tests and encourage patients to present to formal healthcare services. This was facilitated by recruited healthcare surveillance workers, who would visit local IPs quarterly [119]. In West Bengal, IPs expressed enthusiasm for both financial incentives but also increased involvement in the TB care process, such as treatment supporter or transportation of sputum samples [120].

This intervention likewise targets barriers linked to the income SDH and material circumstances IDH [7]. However, these initiatives may be held back by the aforementioned funding gap [111] and poor governance [104]. This aligns both with Pillar 1 and Pillar 2 of the WHO End TB Strategy through facilitating integration of disparate elements of the healthcare system, private and public, and early diagnosis and treatment [10]. Furthermore, through training IPs and other HCWs, this intervention promotes progress towards SDG 3, which encourages recruitment and retention of HCWs [9], and multisectoral cooperation, a key element of Quadruple Aim 1 [11]. Considering the high proportion of patients presenting to private providers relative to other high-TB countries [95] and, thus, contributing to the cycle of diagnostic and treatment delays (Figure 5), this intervention would be high-impact and should be prioritised for implementation. A key metric for its efficacy would be a reduction in the proportion of TB diagnoses confirmed after an acceptable delay timeframe of 45.6 days [42].

4.3. Research Gaps

This review has identified several gaps in the existing body of literature that warrant further investigation (

Table 4. Research need by knowledge domain and suggested methodology.

Domain	Discipline	Methodology	Research Need
Initial presentation to TB services	Behavioural Science, Public Health	Interviews and Longitudinal Patient Journey Mapping	Drivers of initial presentation to private hospitals for TB treatment, which are potentially disruptive to DOTS.
Relative influence of TB risk factors	Public Health	Case-based studies	Strength of risk factors present among low-SES TB patients versus those among high-SES.
Kutcha house construction method	Engineering Construction	Surveys on construction methods and associated drivers	Drivers of choice of materials used in kutcha house construction, which account for a majority of residential units and facilitate TB transmission
Incorporate planetary health into existing WHO SDH Framework	N/A	N/A	Incorporate ecological risk factors for disease into the existing WHO Framework to inform more holistic, sustainable epidemiological research and interventions
Efficacy of coordinated community action at improving TB awareness and case notification locally	Public health Behavioural Science	Pilot interventions	Determine whether engaging local community leaders is effective at tackling current misconceptions about TB that may impede case notification

). Addressing these gaps through transdisciplinary research could enhance the effectiveness of TB-related public health messaging, improve resource allocation, and support the development of more targeted policies and clinical guidelines. Longitudinal studies would provide a deeper understanding of the dynamics underpinning TB disparities in Bangladesh, complementing the existing evidence base, which is largely composed of case–control and cross-sectional studies.

Firstly, the drivers behind presentation of low-SES populations to private healthcare and IPs are also somewhat unclear. While high informal payments [58] and long waiting times [59] associated with DOTS are potentially burdensome for low-SES TB patients and contribute to the treatment barrier cycle (Figure 5), user charges, improper referral and treatment and lengthy travel times at private hospitals [50] could likewise act as deterrents to seeking care at these facilities. Therefore, further qualitative research—particularly interviews or longitudinal patient journey mapping—could provide clarity on the relative influence of these barriers.

Secondly, the relative strength of TB risk factors among high-SES populations versus those among low-SES populations (smoking, child malnutrition, and use of biomass fuels), warrants investigation (Figure 3). Current data suggests that more cases are attributed to the low-SES risk factors than the high-SES ones [36]. However, the difference is not statistically significant [36]. Comprehensive case-based studies capturing pre-existing conditions and SES across TB patients could improve understanding of which comorbidities most significantly contribute to the TB burden in Bangladesh, informing more targeted prevention strategies.

Thirdly, research on materials used in kutcha house construction as well as drivers of such decisions is necessary to assess the impact of their associated health risks. The most recently available research on this issue obtained from the literature searches was a participatory survey from 1999, which concluded that building methods were primarily driven by cost constraints [74]. Kutchas still account for a majority of residential units [75] and are associated with elevated intrahousehold TB transmission [15], necessitating updated surveys of construction choices.

Fourthly, the current WHO SDH Framework only highlights material circumstances, behaviours and psychosocial factors as IDHs [7]. Furthermore, contextual elements driving these IDHs are predominantly in relation to human factors, such as economic policies, political governance and socio-cultural values [7]. However, this review has highlighted the significant influence of ecological factors on TB’s disproportionate burden on low-SES populations—namely the prevalence of smoking and use of biomass fuels which worsen air quality in low-income housing and deterioration in urban health highlighted by slum-based TB transmission. Therefore, this review proposes amendments to the current iteration of the WHO SDH Framework to incorporate EDHs into each domain of the framework to inform more holistic, sustainable interventions that tackle social and ecological drivers of disease.

Finally, there are perceptions of TB—the disease being a divine punishment [37], stigma towards sputum testing [45] and exclusionary attitudes towards TB patients [37]—amongst predominantly uneducated and rural demographic groups that may impede case notification and awareness of the disease. Therefore, it may be necessary to engage community leaders to aid in improved awareness of TB symptoms and treatment options available. This has been piloted in several rural districts of Bangladesh in 2005 and 2006 [108] but more up-to-date research is warranted to evaluate their efficacy. This could primarily be through another iteration of pilot interventions conducted locally with case notification measured post-intervention. The results of this research could inform an additional intervention that has the potential to tackle diagnostic concealment. If effective, it would align with End TB Strategy Pillars 1 and 2 [10] as well as the Quadruple Aims 1 and 2 [11].

4.4. Limitations

This paper is subject to limits of narrative reviews [121]. This review’s identified keywords for database searching may not have been fully exhaustive and could have led to the unintentional exclusion of relevant literature. The authors attempted to compensate this with a thorough snowballing process and utilisation of multiple databases for keyword input. Furthermore, the nature of this review involved the author interpreting research findings to identify further content that could explain mechanisms for the findings. The process of deducing potential explanatory mechanisms is inherently subjective. This was mitigated by rigorous evaluation of the theories proposed in this review by both authors as well as drawing on international comparisons. Additionally, reproducibility is limited by non-systematic selection of keywords, multiple searches being conducted where keywords were not required to be reported by narrative review protocols [121]. Lastly, the authors’ position as external to Bangladesh meant that their analysis may not be wholly comprehensive due to assumptions and preconceptions related to the country’s national development and degree of social equality and cultural values. This is despite a substantial effort to understand local dynamics related to the Tuberculosis burden.

5. Conclusions

This review identified five IDHs through which the SEDHs influence the tuberculosis burden in Bangladesh. These mechanisms include: the concentration of TB risk factors among low-SES populations; overcrowding and poor housing quality; stigma and treatment-seeking behaviours; diagnostic and treatment delays and disruption; and occupational exposure. While these factors predominantly contribute to a disproportionate TB burden among low-SES populations, this association is attenuated by the relatively high diabetes prevalence among high-SES populations. To address these inequalities, this review issues four key recommendations that broadly align with Quadruple Aims towards planetary health systems, UN SDGs and the WHO End TB Strategy: streamlining access to diagnostic and treatment services; reducing overcrowding in homes and workplaces; promoting gender equity in educational attainment; and integrating public, private, and informal healthcare providers. Future research should investigate patient trust in frontline HCWs, the drivers of initial presentation to private providers and IPs, the relative influence of different TB risk factors stratified by SES, construction practices for kutcha housing and amending the WHO SDH Framework to incorporate ecological determinants of health. Generating evidence in these domains will be essential for understanding dynamics of TB spread and designing future, sustainable interventions.