Our study confirmed the occurrence of a high prevalence of DCS and IHD, with 10,836,004 deaths from DCS and 3,264,828 deaths from IHD in Brazil between the years 1980 and 2019 and a downward trend in mortality rates of DCS and IHD over the period. However, this decrease was uneven across the country's federative units and geographic regions and was more prominent in the South and Southeast regions, which have greater socioeconomic development, and the Northeast region, while the rates remained stable in the North and Midwest regions. This observation is consistent with reports from previous studies, including those pointing out an uneven decrease in the number of deaths from DCS between 1990 and 2015 across the country's geographic regions, more pronounced in states in the South and Southeast regions and less pronounced in the North and Northeast regions.10,11,12 However, these studies did not evaluate the relationship between the differences in mortality trends and social determinants while only reporting the decreasing mortality as less prominent in regions with greater development.
A study evaluating the association between mortality from DCS in municipalities of the state of Rio de Janeiro from 1979 to 2010 and the Gross Domestic Product (GDP) per capita obtained from the Institute of Applied Economic Research (Instituto de Pesquisa Econômica Aplicada, IPEA) showed a decrease in mortality from DCS associated with a GDP increase with a time lag of more than 10 years.13 In 2018, another study evaluating the association of DCS, hypertensive diseases, and cerebrovascular diseases with the HDI between the years 2004 and 2013 showed a significant inverse association between socioeconomic factors and mortality from these diseases.14
Our study went even further by carrying out this analysis over a longer period – from 1980 to 2019 – and comparing socioeconomic factors with DCS and IHD mortality rates focusing on vulnerability. To accomplish this, we used two different social determinants in our analysis. The first was the MHDI, which is more commonly used and previously applied in other studies incorporating assessments of health, education, and income with an interval between the index and the result of more than 10 years. The second was the SVI, which is a lesser-known and makes our analysis unique when applying this index that has not been used in previous studies on DCS and IHD mortality rates, expanding analysis to vulnerability. Given the absence of studies with this indicator, there is no data in the literature on the time required between the change in the index and its influence in DCS and IHD.
The present study showed an inverse relationship between the MHDI of the Brazilian federative units and the standardized mortality rates of DCS and IHD, both absolutely and relatively, with a more pronounced decrease observed in the federative units with the highest MHDI. The results suggested a possible advantage of a good absolute MHDI than a progressive improvement of this index. There was a directly proportional relationship between the SVI and the standardized mortality rates of DCS and IHD, suggesting that the lower the SVI, the lower the mortality rate from these causes. As in the MHDI analysis, the absolute SVI value appeared to be more relevant than the relative improvement of this index. Our study showed no differences when using older HDI or SVI data, reinforcing that the absolute value of the indices is probably the most important. Therefore, the more developed and least vulnerable the federative unit, the lower the mortality rate from DCS and IHD and the greater the decrease in mortality rates due to these diseases.
Naturally, we must keep in mind the genetic influences associated with the development of DCS and IHD, in addition to lifestyle habits associated with risk factors such as a diet rich in salt and fat, obesity, sedentary lifestyle, alcohol consumption, and smoking. The initial step toward improving the high incidence rates of cardiovascular disease in Brazil is to invest in human development across different regions of the country and reduce social vulnerability to allow for the fulfillment of the constitutional rights of each citizen, including, for example, access to education and awareness of the possible causes of the diseases addressed in this study, access to food appropriate to the individual's nutritional requirements, quality housing and health, as well as access to medications, prophylactic methods, and adequate medical treatments.
In short, in view of the relationship observed in this study between the HDI and the frequency of DCS and IHD in the population, it is important to emphasize the importance of government investment in the social and economic development of the country's microregions and the nation as a whole as a way of maintaining public health.
Limitations of this study include its observational design, which does not allow for a causality conclusion but raises hypotheses and awareness that can help implement important political, social, and administrative measures. The presented data demonstrate that the progression of the social development indices analyzed in the study is accompanied by improved results of mortality from DCS. Another relevant limitation of this study is the fact that the information was retrieved from a database, which has possible biases generated by data entry errors like deaths attributed to ill-defined causes, underreporting, and garbage codes.25 Finally, another limitation is the possibility of an ecological bias as mortality is assessed at an individual level, but social determinants are being measured at the group level, but is an issue inherent to the theme, because, when you are analyzing social determinants, you work on the community spectrum. This is even clearer when we think of vulnerability as this indicator, by definition, deals with the failure of a given community to meet basic needs, with no individual data available on this theme.