This study aimed to investigate the factors associated with NCD comorbidities and the health service utilization in Pulmonary Tuberculosis patients enrolled in Indonesia's National Health Insurance. A total of 27,449 Pulmonary Tuberculosis patients were identified, with 11.8% of them having NCD. Our study found that age is one of the predictors of NCD comorbidity in Pulmonary Tuberculosis patients, it was clear that older patients were more likely to have NCD comorbidity compared with a younger patient, this result is in line with finding from a study in Gabon [4]. In that study, individuals aged over 55 years was associated with diabetes (aOR 6·99; 2·10–25·44) and hypertension (aOR 7.48; 2·36–25·30) in multivariable analysis. Similiarly, a study in Southern Ethiopia reported the same result that individuals aged over 50 are at 22.13 (3.46, 141.41) times higher risk than those aged 20–34 years of developing TB with multi-comorbid NCD [17]. Addresing health in the elderly presents a public health challenge, the elderly are at greater risk of vulnerability due to their nature of physical and functional health risks [18].

Contrary to the previous study [19], this study did not find an association between males and tuberculosis NCD comorbidity. Our study reported that married patients are more likely to have NCD comorbidity, which is consistent with findings from a study conducted in South Africa. However, there is a different result in divorced patients [19]. Previous studies reported that the highest prevalence of Tuberculosis was observed in Sumatera [20], and our study also reported the same finding. It was also noticed that the highest prevalence of NCD comorbidity in pulmonary tuberculosis patients was also in Sumatra followed by Java (Table 1). This could have been a result of the extensive availability of healthcare facilities in Sumatra and Java islands in comparison to other islands [20].

The highest proportion of NCD comorbidity among TB patients was reported in poor and underprivileged individuals with the support of the central government. Previous studies support the findings that populations with lower socioeconomic status are at an elevated risk of developing NCD—diabetes, stroke, myocardial infarction (heart attack), and cancer [21, 22]. An unhealthy lifestyle especially food choices may have a high contribution to the NCD. Industrialization and global food market dynamics impact food choices amidst constraints such as limited household income, time availability, and household and community resources. Additionally, risk factors for non-communicable diseases (NCDs) are exacerbated by low household income and the poverty of environments inhabited by low-income individuals, limiting opportunities for physical activity among those in sedentary occupations. These circumstances underscore the minimal control individuals often have over their diet and exercise routines [23].

Our study showed slightly higher COPD prevalence (4.71%) among active pulmonary compared to the study conducted in Tanzania. In the Tanzanian study it was reported that among COPD patients there was a 10% prevalence of patients with a history of pulmonary tuberculosis but currently inactive or already cured and 3% prevalence of patient with current active tuberculosis suspected to have COPD [24]. A meta-analysis study reported that individuals with prior infection of Pulmonary tuberculosis have a greater risk of developing Chronic Obstructive Pulmonary Disease [25]. Based on WHO estimation, Indonesia is ranked second with the highest TB burden. In 2021, the TB incidence rate is 354 per 100.000 population and the TB mortality rate is 52 per 100.000 population [2]. Based on the WHO estimation, it is known that Indonesia has a greater tuberculosis burden compared to the country in the African region. It was noted that post-tuberculosis lung damage is a recognized consequence of pulmonary TB [26] and is positively associated with pulmonary function impairment, leading to frequent respiratory symptoms [27]. However, the interrelationship between TB and COPD is very complex [28]. Our study reported that the prevalence of Diabetes Mellitus comorbidity in pulmonary tuberculosis patients was far less than in a previous study done in Indonesia [12, 29]. The difference in the data collection method and study population could explain the variations in results across the studies.

Our study only accounted for the pulmonary tuberculosis patients who accessed referral care using the national health insurance scheme in 2021. It should be noted that the Indonesia government has already enhanced the screening and treatment of pulmonary tuberculosis together aligned with Diabetes Mellitus screening in the primary health center [2], even though these efforts are still not evenly distributed throughout Indonesia.

Cardiovascular disease was well known as the secondary disease that could be developed in people with active pulmonary tuberculosis. Approximately 60% of patients with TB have a cardiovascular disease [30]. Yet, commonly underestimated due to a lack of suspicion [31]. The association between tuberculosis and lung cancer has been discovered, it is stated that the mycobacterium tuberculosis infection accelerates the development of lung cancer [32]. Studies in South Korea reported that younger patients with TB have a more substantial likelihood of lung cancer than older patients with pulmonary TB [33]. A Cohort study done in the United Kingdom and China reported that chronic kidney disease (CKD) is associated with an increased risk of active Tuberculosis [34, 35]. Mental health was reported as the comorbidity of Tuberculosis. According to the WHO, Tuberculosis patients have a higher risk of mental health conditions, which can negatively impact tuberculosis treatment, quality of life, and other health and social outcomes [36].

It is noted that the patients with NCD comorbidity require more inpatient health services compared to the people without NCD comorbidity. A previous study reported that the existence of NCD comorbidity in Pulmonary Tuberculosis patients is highly associated with decreased physical health [19]. A systematic review has shown  that individuals with multimorbidity conditions require more outpatient and inpatient care [37], which is also supported by our study. Additionally, It was observed that the subsidized patients significantly contribute to the utilization of inpatient health services. This poses a threat to the National Health Insurance scheme, as it has been reported to consistently incur severe deficits [38].

Tuberculosis and non-communicable diseases share a similar multiple risk factor [39], suggesting that integrating both Tuberculosis and NCD screening and treatment programs could potentially enhance the treatment outcomes of both tuberculosis and NCD simultaneously. Indonesia has developed a national screening program that integrates tuberculosis with Diabetes Mellitus [2, 13]. The effective result of the integration of tuberculosis and diabetes mellitus was reported in a study conducted in Jakarta, Indonesia, and Luanda, Angola, where receiving Diabetes Mellitus treatment was associated with a higher likelihood of completing TB treatment [40, 41]. However, a systematic review analysis concluded that the integration of tuberculosis and Diabetes Mellitus was weak to enhance both treatment outcomes [40]. Another qualitative study in Yogyakarta, Indonesia reported that there were barriers existing in delivering the tuberculosis–diabetes mellitus integration program. The barriers were health services-related barriers, patient-related barriers, and health provider-patient interaction-related barriers. To enhance the health outcomes of the program, effort to minimize the existing barriers should be considered [42].

The integration impact of tuberculosis–diabetes mellitus has been proven to some extent to enhance the program outcomes. However, the integration program on other NCD comorbidities was nowhere to be found. Given the numbers needed to test to detect a new case for each of the non-communicable diseases, it seems feasible to incorporate routine screening of pulmonary tuberculosis and secondary prevention of common NCD. However, it should be noted that systematic screening for non-communicable diseases during pulmonary tuberculosis care would require capacity building and a more inclusive focus on the patient’s health outcomes. The national tuberculosis control program in many LMICs integrated successfully the screening of HIV in tuberculosis patients. Therefore, extending the program to NCD comorbidity may not be a huge challenge to provide a new scheme in health service delivery.

Our findings highlight the crucial significance of enhancing relationships between TB and NCD control programs to strengthen the management of TB-NCD comorbidities. Integrated care can significantly improve the efficiency of health service delivery, particularly in resource-constrained settings. There is an urgent need to realign and improve healthcare system responses to establish effective screening programs that prevent and control NCDs using cost-efficient interventions and well-structured, integrated methods to provide high-quality primary care. Equal preventative and treatment approaches are also essential. The expanding prevalence of double-burden diseases must be recognized as a potential hazard to the stability of Indonesia's national health insurance scheme.

The strength of our study was the enrolment of a large number of participants from the NHI sample data that could cover the national sampling coverage. The diagnosis to confirm the patient was based on the laboratory and medical confirmed ICD X code, therefore misclassification could be minimalized. There are some limitations of our study due to the nature of using secondary data, some other related variables correlation could not be addressed such as the severity level of the diseases and health behavior of the patients. Indonesia's health insurance system uses a referral policy, in which patients should receive treatment from the primary level before going to the referral facility [43]. Therefore, most tuberculosis patients who do not have any severe complication condition are less likely to receive treatment in a referral hospital. With this fact, our study may only report a small part of the tuberculosis patients with non-communicable disease comorbidity. Consequently, the findings may not represent the entire population of pulmonary tuberculosis patients in Indonesia.