Due to poor sanitation in rural and weak health awareness among rural people, 80% of the patients are rural people and migrants, and rural areas are areas with a high incidence of tuberculosis in China[19],[20]. However, previous studies have focused on TB deaths across the population of China, while ignoring trends in TB deaths among rural people[15–18]. This study analyzes the mortality rate of tuberculosis among rural people in China and discusses the high-risk groups of tuberculosis in rural China and the effectiveness of prevention and control measures.
The mortality rate of tuberculosis among rural people in China from 2006 to 2020 showed a downward trend, indicating that a series of policies introduced by the government were effective. Since 2006, China has introduced and implemented a number of international cooperation projects, carried out baseline investigation of drug resistance, and fully implemented the Modern Tuberculosis Control Strategy (DOTS Strategy)[24, 25]. In 2016, the government issued the "Healthy China 2030" plan, exploring new management models for tuberculosis patients, conducting research on the treatment of tuberculosis and AIDS co-infection, carrying out the prevention and treatment of drug-resistant tuberculosis, and implementing a new tuberculosis prevention and treatment service model of "trinity" of the Center for Disease Control and Prevention, hospitals and township health centers[26–28]. In 2017, the Chinese government proposed the 13th Five-Year Plan for National Tuberculosis Prevention and Control, which mentioned that it is necessary to increase pathogenic examination and drug resistance screening, strengthen the construction of tuberculosis prevention and control informatization, and gradually realize the whole process of information management of tuberculosis patients[15, 29].
Age effects are related to the biological and social processes of aging specific to an individual, including physiological changes and accumulation of social experiences associated with aging[30–32]. The relative risk of TB death among rural people increased with age, and the risk increased significantly faster in rural females from age after 60 years, mainly due to the high incidence of atypical symptoms and complications and adverse reactions after onset. On the one hand, elderly tuberculosis patients have hidden clinical symptoms, and the proportion of fever, hemoptysis, chest pain and other symptoms is lower than that of young patients[33]. It is easy to misdiagnose chronic bronchitis, lung infection and emphysema in the clinical diagnosis process, and if the patient itself is accompanied by respiratory diseases, it is easy to be misdiagnosed as recurrence of respiratory diseases or aggravation of symptoms, thereby delaying the treatment of tuberculosis[34]. On the other hand, the elderly are prone to other respiratory diseases, especially lung infections and respiratory failure, the proportion is significantly higher than that of young and middle-aged patients, because the elderly patients have poor immune function and most of them are more serious, which makes the chance of nosocomial infection significantly increased[35]. Pulmonary infection can precipitate or exacerbate underlying lung disease in older people, leading to respiratory failure. Finally, adverse reactions may occur due to reduced liver blood flow, decreased liver enzyme activity, reduced rate of drug biotransformation and synthesis reaction in the elderly, and prolonged drug half-life[36]. The plasma protein synthesis of the elderly decreases, reduces the protein binding rate of the drug, and increases the free part to increase the adverse drug reactions, which affects the patient's treatment compliance and the completion of the course of treatment, thereby reducing the cure rate[35].Rural males became a risk factor from age after age 35, and the risk of death rose rapidly, which may be due to the need for work and the need for rural males to continue to move, coupled with increased living pressure, age after age 35 becomes a risk factor.
Period effects are the result of external factors affecting all age groups equally at a given calendar time, and may result from a range of environmental, social and economic factors[30–32]. The risk of death decreased for both rural males and females, and the period effect shifted to a protective factor from 2011 to 2015. This may be related to the reform of the TB service system. China's tuberculosis treatment service system changed from being provided by CDC or specialized pharmacies to designated general hospitals [37]. Doctors in hospitals are more professional than CDC staff, able to provide better medical services, and better able to meet the needs of patients. This is consistent with previous studies [37, 38]. In addition, this study found a gradual slowdown in the decline in the risk of death, which may be related to the slow progress of new TB tests, treatment regimens, and vaccines at the same time as the service system was transformed [39]. risk of death among rural men increased between 2016 and 2020, which may be related to the outbreak of the new crown epidemic [40]. On the one hand, the outbreak of the COVID-19, medical services and resources that originally belonged to tuberculosis gave way to COVID-19 prevention and control, resulting in insufficient basic tuberculosis services[41, 42]. COVID-19 and tuberculosis are both respiratory diseases, and there are certain similarities in diagnosis and treatment, and some anti-tuberculosis drugs coincide with drugs for the treatment of COVID-19, resulting in drug shortages and price increases, which in turn makes patients stop taking drugs[43]. On the other hand, the isolation measures adopted for the COVID-19 have made it more difficult for tuberculosis patients to be detected and treated in time[44].
The birth cohort effect is the sum of all exposures that the cohort experiences from birth[30–32]. From 1924 to 1949, China was at its highest risk of death from birth sequence during the War of Resistance Against Japan and the War of Liberation, when the war made tuberculosis spread more widely and rapidly, the health system was destroyed and patients could not receive adequate treatment[16]. In the early days of the war, due to the influence of traditional Chinese thinking, men mostly worked outside the home, and women were mostly active at home or not far from home, so men were more likely to get sick and then have a higher risk of death due to poor medical services[45]. As the war progressed, many male patients died in the war as a result of being drafted as soldiers, so the risk of death from tuberculosis in the birth cohort was reduced, and the risk of death increased for women, mostly at home, due to lack of medical care due to poverty or the collapse of the health system[46]. From 1952 to 1978, China launched a patriotic health campaign and initially established a relatively complete health system [47], and the cooperative medical system was implemented in rural areas, which fully guaranteed the health of rural people, and the risk of death in the tuberculosis birth cohort for both men and women continued to decrease, and the birth cohort of rural people was no longer a risk factor. After 1978, China entered the period of reform and opening up, began to actively study foreign health policies, combined with its own patriotic health campaign, carried out a number of national tuberculosis epidemiological sample surveys, carried out exploratory health reform and explored the possibility of trying to adapt to China's medical system[48–50]. Due to the transition from a planned economy to a market economy, new rural cooperative medical care was set up in rural areas, and the cost of personal medical care continued to increase, resulting in an overall downward trend in the birth queue of rural people, but in some years it increased[51].
Limitations
This study has some limitations. First, because tuberculosis patients are often combined with other diseases, such as chronic obstructive pulmonary disease, asthma, pneumoconiosis, etc., when tuberculosis patients die, it is difficult to determine whether the cause of death is tuberculosis or other combined diseases. Therefore, when CDC counts tuberculosis mortality data, it may include some patients who died from other diseases in tuberculosis mortality data, making tuberculosis mortality data biased. Second, due to the lack of public data on tuberculosis mortality in rural areas, this study used the mortality data of Chinese rural people from 2006 to 2020, with a short time span, and the results may have limitations. Thirdly, although the IE algorithm used in this study does not require model assumptions and has excellent results, the principle of the method is relatively complex, and the practical significance of parameter estimation needs further research. Fourth, because the number of deaths from tuberculosis other than pulmonary tuberculosis in the data is small, it is impossible to analyze each tuberculosis separately.