Epidemiological Patterns of Hypertension and Type 2 Diabetes Mellitus in Vietnam. Ecological Study

Vietnam is a SEA country with a high burden of NCD and hypertension and diabetes are among the top contributors to premature mortality. The recent reviews reported the rapidly growing prevalence of these two chronic conditions in Vietnam. To investigate the epidemiological burden of HT and DM type 2 in Vietnam an ecological study employing secondary data analysis was conducted. The study was a part of the SUNI SEA project implementation with the aim to put the basis for the research hypothesis for the SUNI SEA project in Vietnam. Data from the Institute of Health Metrics and Evaluation and Vietnamese Health statistics years books were analysed by linear and polynomial regression analyses, Kendall rank correlation and Pearson correlation. On average 19% of all deaths and 9% of all DALYs were associated with high SBP and 2% of all deaths and 2% of all DALYs were attributable to DM type 2 between 1990-2017 in Vietnam. Differences between genders were recognizable mainly in CVDs and high SBP death rates. The decrease in the number of elementary nurses, as well as the increase in health insurance expenditures per inpatient, seems to be with the highest certainty correlated with HT and type 2 DM death and DALYs rates. If the tracked progress remains at the same pace, in the category of Good health and well-being Vietnam seems not to be able to achieve the desired threshold by 2030 as committed by United Nations Member States in 2015. Developing regulatory frameworks and social demand for professionalism in Vietnam could encourage nurses to pursue higher education but the essential role of elementary nurses became more sensible. The health nancing reform that shifts resources from hospital care to primary care should be developed to improve access to early diagnosis and chronic care. of elementary nurses, as well increase in health insurance expenditures per inpatient, seems the highest certainty correlated with HT and type 2 DM death and DALYs rates.


Introduction
Non-communicable diseases (NCDs) have become the leading causes of the global burden of disease, accounting for two-thirds of mortality worldwide 1 , and three quarters occurred in low-and middle-income countries. Cardiovascular diseases (CVDs) are responsible for the largest proportion of these burden contributing to a third of NCDs burden 1,2 . Hypertension (HT) is one of the strongest risk factors for CVDs, which was the leading cause of premature death globally 3,4 . There is a strong association between diabetes mellitus (DM) type 2 and CVDs, which is the most prevalent cause of morbidity and mortality among patients with DM 4,5 . The incidence of HTN and DM keep rising and these two diseases are among the most prevalence and costly chronic disease worldwide 4,6 . The prevalence of HT and DM type 2 among adults is similar or higher in low-and middle-income countries than in high-income countries because of sharper prevalence increase in the past few decades 7,8 .
In 2008, 14.5 million total deaths were estimated in countries of Southeast Asia (SEA) with 7.9 million (55%) attributable to NCDs. CVDs alone accounted for 25% of all deaths, of which HT is responsible for nearly 1.5 million deaths annually 9 . The prevalence of diabetes is also growing at alarming rates and has almost doubled in many SEA countries between 2005-2015 10 . Vietnam is a SEA country with a high burden of NCD and CVD and diabetes are among the top contributors to premature mortality 11 . The recent reviews reported prevalence of HT and DM is estimated to 21.8% and 5.4% respectively and signi es a rapidly growing prevalence of these two chronic conditions in Vietnam 12 .
The 2030 Agenda for Sustainable Development recognizes NCDs as a major challenge for sustainable development. All the member countries have committed to developing a national action plan for combating NCD and achieving NCD-related goals. In the context of high NCD associated burdens in the SEA region, the SEA countries endorsed several policy frameworks and national programs, such as the South-East Asia Regional Network for Prevention and Control of Noncommunicable Diseases in 2005 or the Action plan for the prevention and control of NCDs in SEA 13 . One of these endorsements is project Scaling-up NCD Interventions in South East Asia (SUNI-SEA), which is currently ongoing in three SEA countries (Vietnam, Myanmar, and Indonesia). The project aims to validate effective scaling-up strategies of evidence-based DM and HT prevention and management programs and to enhance sustainable action for the achievement of the Sustainable Development Goals, based on experiences in SEA 14 . This study was a part of the SUNI SEA project implementation with the aim to put the basis for the research hypothesis for the SUNI SEA project in Vietnam. For this purpose, we described and assessed the scale of the burden of CVDs, HT, and DM type 2 respectively, and attached nancial and contextual factors affecting its progress.

Methodology Study design and population
To investigate the epidemiological burden of HT and DM type 2 in Vietnam we conducted an ecological study employing secondary data analysis. For a study population, we included all Vietnamese populations between the years 1990-2017 (no exclusions based on different attributes e.g. race or age were made).

Data sources
Data from the Institute of Health Metrics and Evaluation were accessed using the Global Burden Disease (GBD) Results Tool 15 . In the database, the ICD 10 coding was used. Albeit the wide range of the con dence intervals limiting the validity of these results, these data belong to the most appropriate among accessible data sources up to date 16 . Data were age-standardized using the GBD reference population by researchers in the Global Burden of Disease Study in 2017 17 .
The data from Vietnamese Health statistics years books published by the Vietnamese Ministry of Health were analysed for nancial and contextual factors (human resources, health insurance, health expenditures, etc.). The yearbooks published between 2009 and 2016 were selected (in total 8 yearbooks) 18,19,20,21,22,23,24,25 . Because of changes in reports we excluded the yearbooks before 2009 due to missing or incomplete data.

Variable de nitions
To analyse the epidemiological situation of CVDs and DM type 2 we used variables Cardiovascular diseases (code B.2) and Diabetes mellitus type 2 (code B.8.1.2) coded under the Causes category in GBD Results Tool. For the purpose of this study, the burden of hypertension was assessed by variable High systolic blood pressure (SBP ≥ 110-115 mm HG) coded under Risk factors from all causes' category.
Selected nancial and contextual factors represented: citizens per 1 health personnel, the average number of medical consultations per capita, and health expenditures from health insurance per inpatients and outpatients. In the category of health personnel, 23 professions were identi ed and for the clarity of the study results, some of them were clustered (College and university nurse with Second-degree nurse to Higher degree nurse) or excluded based on the relevance to the aims of the study (pharmacists, midwives, etc.).

Statistical analysis
To assess changes in CVDs, high SBP, and DM type 2 death rates and DALYs over time the data were analysed by linear and polynomial regression analyses and Kendall rank correlation. To estimate the correlation between these variables and selected nancial and contextual factors the Pearson correlation coe cient was used. The statistical analysis was performed in the R project software 26 .

Results
As the Sustainable development goals index related to health has increased over time in Vietnam (from 29 in 1990 to 46 in 2015), we observe the widening gap between the distribution of the health burden of communicable (CDs) and non-communicable diseases (NCDs). Overall, the estimated deaths from NCDs represented 78% of all deaths, and estimated DALYs from NCDs represented 73% of all DALYs in Vietnam in 2015. The differences between CDs and NCDs deaths and CDs and NCDs DALYs over time are statistically signi cant (p < 0.001; see Appendix 1).
Deaths caused by CVDs represented 31% of all deaths in Vietnam in 1990-2017 on average, out of which 57% were attributable to high systolic blood pressure (SBP). Similarly, out of 15% of all DALYs which were attributable to CVDs, 56% were caused by high SBP. Overall, on average 19% of all deaths and 9% of all DALYs were associated with high SBP and 2% of all deaths and 2% of all DALYs were attributable to DM type 2 between 1990-2017 in Vietnam. The proportions of deaths and DALYs attributable to CVDs, high SBP, and DM type 2 were steadily rising between 1990-2017 in Vietnam (Fig. 1).
Between the years 1990-2017, there was an increase in mortality for both males and females in all observed variables -CVDs, high SBP, and DM type 2 (Fig. 2). Differences between genders were recognizable mainly in CVDs and high SBP death rates. As for DALYs are the results similar except the CVDs DALYs rate in females which tend to decrease over time, but not signi cantly (Fig. 3). For more details see appendix 3 and 4.
Between the years 2009-2016 has in Vietnam signi cantly increased heath personnel capacities, mainly in the category Bachelor of Public Health (or higher) and among high degree nurses. On the contrary, as many of the nurses persuaded higher education levels there is a signi cant increase in the number of citizens who pertain to 1 elementary nurse. Over the years the increase is observed also for assistant doctors and traditional medicine practitioners (Table 1).  From the results of correlation analysis with relatively narrow con dence intervals (range of 0.1), only two selected contextual variables were identi ed. The increasing number of citizens per 1 EN was positively associated with all six main variables -CVDs, high SBP, and DM type 2 death rates and DALYs rates. Increasing health insurance expenditures per inpatient were also positively correlated to these variables except DM type 2 DALYs rate with a little wider 95 CI% (0.11). 95% con dence intervals in correlation analysis were in all other variables wider (Table 3). The variables as citizens per 1 assistant doctor, average number of medical consultations per capita, and health insurance expenditures per outpatient were in strong correlation with CVDs, high SBP and DM type 2 death and DALYs rates (positively or negatively), however with extremely wide con dence intervals and with a p-value greater than 0.05 (see appendix 4).

Discussion
The health burden of many NCDs in Vietnam has increased over the years since the 1990s, with death rate increased up to almost 78% of all deaths that are attributable to NCDs in 2015. A similar situation affects the whole Southeast Asia region ranging from 45% in Timur-Leste to 85% in Brunei Darussalam in 2016 27 . The proportion of DALYs attributable to NCDs in Vietnam since the 1990s as well as the proportion of NCDs mortality is progressing accordingly to an estimated proportion of NCDs DALYs and deaths for countries with middle socio-demographic index 28 . However, if the tracked progress remains at the same pace, in the category of Good health and well-being Vietnam seems not to be able to achieve the desired threshold by 2030 as committed by United Nations Member States in 2015 29 .
The Vietnam health workforce reform has been underway in Vietnam, which were strongly committed in the master plan for Vietnam'  34 . Health insurance expenditures per inpatient (HIEpI) in Vietnam signi cantly increased within the past few years and as such will be needed to handle in the future. In our analysis, the increase in HIEpI was in strong correlation with an increase in CVDs, high SBP, and DM type 2 death and DALYs rates. Such ndings can be understood as such utilization of inpatient services is more likely linked with serious NCD-associated conditions and complications. The health nancing reform that shifts resources from hospital care to primary care should be developed to improve access to early diagnosis and chronic care and thus mitigate serious NCD-related complications and its associated economic burden of health expenditure on the population.
The increasing CVDs, high SBP, and DM type 2 death rates and DALYs rates since the 1990s in Vietnam become more differentiated between males and females as we go further into the present. Albeit males have signi cantly higher rates attributable to CVDs and related to high SBP, DM type 2 death rate as well as DALYs are higher in the female population. Even if it has been recognized in the past that the impact of DM type 2 is greater in females than in males for all causes it is not yet fully understood 35 . Possible explanations could be the different cardiovascular risk pro le or quality of provided health care but these need to be further examined 36 . The pooled prevalence of HT in Vietnam is estimated to be 21.1% 37 which is lower than HT overall prevalence 27% estimated for member countries of the South Asian Association for Regional Cooperation 38 , 37.8% in middle-income countries or 23.1% in low-income countries 39 . The rate of change in both HT and DM type 2 death rates (increase in these cases) is however much faster than in high-income countries 40 .
Within the estimated burden attributable to CVDs which is expected to further rise in the Southeast Asia region over the next several decades 41 , the policymakers will have a fundamental role in tackling its progress in Vietnam. The economic utility in the implementation of preventive measures to reduce the health burden of both HT and DM type 2 has been demonstrated many times in the past 42

Limits of study
Limits of the study emerged from the type of data used. First, the ecological character of this study limited our inference possibilities about the individuals thus conclusions must be taken with caution and should serve as the basis for further analysis. Second, we were not able to perform a more advanced time trend analysis of HT and DM type 2 because of the lack of monthly (or quarterly) diversi cation of reported statistical data. Third, the standardization was performed by GBD 2017 researchers using the GBD reference population, which is not often used. Consecutive comparisons and their interpretations were thus limited to assess progress in time rather than a comparison of speci c numbers or rates. And fourth, we were limited by the availability of data on health personnel in the past in Vietnam, as the analysis of older data could reveal further differences.

Conclusions
The burden of CVDs has risen signi cantly since the 1990s in Vietnam and this progress seems to continue if the government will not endorse effective precautions. Although the health workforce has increased signi cantly over the years, it still has not achieved the WHO standards, and HT and DM type 2 death rates, as well as DALYs, affect more Vietnamese people each year. Moreover, since 2010 female's death and DALYs rates are increasing at a much higher pace (in all three selected variables). The decrease in the number of elementary nurses, as well as the increase in health insurance expenditures per inpatient, seems to be with the highest certainty correlated with HT and type 2 DM death and DALYs rates. Not applicable -because of the ecological character of the study employing aggregated data from routine statistics, there was no need for ethical approval.

Consent for publication
Not applicable.

Competing interests
The authors declare that they have no competing interests.

Funding
The research leading to these results was done within the framework of the SUNI-SEA project and has received funding from the European Commission under grant agreement no 825026.
Authors' contributions PS analysed data and was a major contributor in writing the manuscript. HGN adjusted the discussion section to the Vietnamese setting and contributed to the methodological approach. MJ and PD contributed to the theoretical background of the manuscript and statistical analysis. MM grammatically adjusted the language of the manuscript and provided statistical analysis veri cation. RM led the methodological approach in the manuscript, provided consultations to all issues, and adjusted the overall manuscript form.
All authors read and approved the nal manuscript.