To our knowledge, ecological studies of the TB burden have been carried out in America, Europe and Africa[5,9-11].But such research is limited in China. This paper provides original, large population and long-term based data on the relationship between economy and TB registered incidence in the second largest province located in the eastern coast of China.Our findings show a clear ecological association between the economic development and TB registered incidence.Rural annual net income and per capita medical expenditure have significant negative effects on the registered incidence. With the increase of the above two indicators, the registered incidence shows a decreasing trend.The influence of medical expenditure on the registered incidence rate is greater than that of rural annual net income.This result corroborates the findings of a recent global analysis that social protection spending is strongly associated with lower tuberculosis case notification, incidence, and mortality rates. And it also confirms the report that economic development and increased access to health care both reduce TB incidence.Therefore, the government should formulate more policies to benefit the people, especially in rural areas, to promote the economic development of rural areas and alleviate poverty. More importantly, the government should increase spending on medicine and health care especially in the economically backward countryside,and actively screen for suspicious TB cases to effectively reduce the TB incidence[15,16].
Population density, per capita savings and urban engel coefficient have significant positive effects on the registered incidence. This conclusion confirms previous research that the increased population density increases the burden of TB[17,18].With the increase of such indicators, the registered incidence shows an increasing trend.The urban engel coefficient has the greatest impact on the TB registered incidence.Engel's Coefficient refers to the proportion of food consumption in households.It means that the lower the household income, the larger the proportion of the household income or the total household expenditure spent on food, the larger the engel coefficient, which means the poorer the family is.Naturally, residents will spend less on health care.
Per capita GDP, urban per capita disposable income also have positive effects on the registered incidence.This result is not consistent with previous studies abroad.Their data show that countries with higher GDP per capita have lower incidence and mortality of TB than others among countries with different income levels.For this result, we take into account the increase of per capita GDP and urban disposable income, which means that people's material living conditions become better and more unhealthy lifestyles are derived, and the increasing prevalence of diabetes increases the population's susceptibility to tuberculosis bacteria. Supporting this relationship is a wealth of evidence, with many studies showing that diabetes affects TB registered incidence and treatment outcomes[19-21]. Moreover, per capita GDP is an average indicator. When the gap between rich and poor increases, per capita GDP will no longer be representative.Therefore, we cannot exclude the interference of the above factors.
As we can see from figure 2, on the whole, except for small fluctuations, the registered incidence of TB in all cities showed a downward trend and it fell fastest in poorer regions.The registered incidence of TB in areas with good economic development was lower than that in areas with poor economic development, but the gap was gradually decreasing, and the registered incidence of TB in all regions was gradually stable.The following reasons might explain this phenomenon.First，areas with high economic development have better medical and educational conditions. On the one hand, the hospital’s funding for tuberculosis can be adequate. On the other hand, people's health care awareness is relatively stronger, and the living environment is better. They will use more income for health care, medicines, nourishment, etc., so that the incidence of tuberculosis can be effectively prevented and controlled.Second，Due to economic constraints, people in poor areas will not have a strong awareness to see a doctor unless there is a major illness. Even if they are diagnosed with tuberculosis, compared with people in economically developed areas, their compliance with treatment will be worse. After the country introduced policies launched by WHO such as short-course chemotherapy, free medication, and active screening for tuberculosis before entering school, poor areas benefited more than developed areas. Therefore, while the overall registered incidence has decreased, the registered incidence in poor areas has become more significant. The studies conducted by Kui Liu and Dong D also found that economically underdeveloped areas with a high TB incidence benefit more[22-23].Their research results also confirm our discovery and explanation.
As far as we know,this is the first study in Shandong province to assess the impact of economic development levels on TB registered incidence.Our sample data is large, including seventeen cities in Shandong province. We examined the impact of the following economic factors on TB registered incidence: per capita GDP, urban per capita disposable income and rural annual net income, population density, urbanization rate, per capita medical expenditure and the per capita savings, number of beds per capita , number of doctors per capita, rural engel coefficient, urban engel coefficient.Both linear and nonlinear patterns were explored to determine the relationship between levels of economic development and TB registered incidence.First, we used panel data regression to examine the impact of different economic factors on TB registered incidence.And then we used the TRM to extend the study from a linear framework to a nonlinear one.Through the threshold test, we selected per capita savings as a threshold variable and examined the impact of other economic factors on TB registered incidence at different levels of savings. Furthermore, we divided seventeen cities in Shandong province into three regions with different levels of economic development, and conducted a horizontal and vertical comparison to more directly explore the impact of different levels of economic development on the registered incidence of TB. Overall, increased economic input is critical, and many studies have emphasized the importance of social protection interventions to reduce the burden of TB[24-25].
There are still some limitations in our research.First, there is a bias in the diagnosis and registration of TB patients.Most TB cases are diagnosed on the basis of clinical and radiological evidence, which may lead to some misdiagnosis and missed diagnosis.In poor areas, due to economic constraints, some people with insignificant clinical symptoms may not seek medical care, resulting in fewer TB cases registered than the true number.We have to acknowledge that some cities provided high or low registered incidence of TB. However, the extent of these inaccuracies is not known. Underestimates might arise from under-reporting or under-diagnosis of cases.Nonetheless, we believe CDC estimates are the best data available for TB registered incidence.In future research, perhaps we can reduce the bias caused by misdiagnosis and missed clinics by improving the diagnostic level of imaging doctors and encouraging people to seek medical treatment in time.Additionally, the economic development might not have an immediate effect on TB registered incidence .We considered the problem of hysteresis, but we did not know the specific length of time.Fortunately, the economic development in Shandong province has been relatively stable in recent years due to its traditional and conservative culture.In future studies, we may be able to establish a model of the delay effect between the economy and the TB registered incidence,making the study more scientific.In addition,from 2007 to 2008, the TB registered incidence increased in all areas in Shandong province and it peaked in 2008 in both poor and moderate regions.But we didn't find a possible reason for this,so further research is needed.Moreover,if we can completely separate urban and rural areas and explore the relationship between economic indicators and TB registered incidence separately, it will be more scientific.But according to our national conditions,it is difficult to distinguish between rural and urban populations completely and accurately.As far as most provinces in China (including Shandong Province) are concerned, many people live in cities although they are registered in rural areas. However,we do not know the specific proportion.So the TB incidence in each city is the total incidence of the city’s urban and rural areas. Finally,TB is preventable and controllable both in groups and individuals,but we acknowledge that the study might not necessarily be applicable on an individual level.It can only provide certain research basis for the prevention and control of TB by relevant departments.We have not estimated the registered incidence in China. Whether these results can be used in other provinces of China and globally is controversial.
These results would strengthen the analysis and provide information for the government departments,guiding them to make economic investment decisions in TB control.For example, the government should focus on increasing economic investment in poor areas to shorten the gap between rich and poor.Relevant health departments should formulate the point-to-point support policy of the third-class hospitals for rural township hospitals, provide special training for tuberculosis diagnosis and treatment for doctors in township hospitals, and regularly carry out tuberculosis free diagnosis activities, and increase the publicity of tuberculosis-related knowledge, and reduce some tuberculosis special inspection costs. The above measures are helpful for the early detection, early diagnosis and early treatment of tuberculosis patients.A more refined measurement of economic investments on a provincial scale would be helpful to determine which programmes or policies are best at reducing TB burden.The benefits of increased economic investments go beyond TB and would be likely to affect the incidence and mortality of other communicable and non-communicable diseases, especially those with a well documented association with poverty. Our findings suggest that economic investments could contribute to a reduced TB incidence. However, further studies are needed to confirm the relationship between the level of economic development and TB incidence both in developed and developing countries.