INTRODUCTION

Systemic Arterial Hypertension (SAH) is a multifactorial and complex disease, characterized as an important risk factor for the development of cardiovascular and kidney diseases¹. Several impacts can be generated by the high global burden of hypertension: from individual impacts, evidenced by the reduction of the quality of life of hypertensive patients², to economic and administrative impacts on society and health systems.^3,4

Among the diseases that can be developed due to ineffective control of SAH, one that stands out is chronic renal failure, also known as chronic kidney disease (CKD). This disease is characterized by the occurrence of kidney damage of at least three months that can cause changes and the progressive decline in renal function⁵. CKD and SAH are important public health problems worldwide, being highly prevalent in low- and middle-income countries, and there is a direct relationship among them: CKD can be the result of uncontrolled SAH, as well as be responsible for the progression and resistance of SAH. Furthermore, the correlation between these two conditions increases the risk of cardiovascular and cerebrovascular outcomes.^5,6

Recent estimates have shown that the prevalence and incidence of patients undergoing dialysis treatment in Brazil has been increasing significantly. This event is possibly related to the aging process of the population and to the demands for improvements in care and access to dialysis services. As the underlying cause, uncontrolled chronic hypertension stands out for continuing to be the main event related to the development of CKD. Additionally, the overall mortality rate due to CKD also showed an significant increase.^7,8

Due to the global increase in the number of patients with CKD who are developing end-stage renal disease and require kidney replacement therapy, the implementation of measures aimed at improving awareness and early diagnosis is urgent in order to establish early management and treatment, thus preventing the evolution to terminal stages³.

Studies on the global burden of diseases allow identifying and comparing changes in disease patterns worldwide, as well as understanding variations, neglected conditions, risk factors, and the possible impacts generated by the high burden of diseases in different countries, thus serving as an effective tool to assist in the formulation of health policies, in the decision-making of health professionals and researchers, and in assisting the development of prevention strategies⁹.

In this context, our study aims to describe the variations of mortality rate for CKD secondary to hypertension, in Brazil, between 1990 and 2019.

METHODS

This is an epidemiological study, with a quantitative approach and descriptive character, that analyzed data from the Global Burden of Disease Study (GBD), a software that stores global, national, and regional data on diseases, including prevalence, incidence, deaths, and disability-adjusted life years. The GBD is led and administered by the Institute for Health Metrics and Evaluation at the University of Washington, which enables timely, relevant, and scientifically valid evidence to improve health policies and practices.¹⁰

The information used was collected from January 3 to 8, 2022, and was obtained through the latest available version of GBD, version 2019, its online version is available on the Institute’s website (https://vizhub.healthdata.org/gbd-compare/). The tool adopts an uncertainty interval of 95% (UI 95%) considering uncertainties arising from the following components: sample size used, adjustments to data sources for the estimation of all-cause mortality, regression model specifications for Gaussian space-time processes, model life table systems, and specifications and estimations of the specific cause model.¹¹

The data presented in this study refer to mortality from chronic kidney disease secondary to hypertension, in Brazil, from 1990 to 2019. The analysis lists the mortality rate per 100,000 inhabitants, adjusted by federative units; the comparison of mortality in Brazil in 1990 and 2019; and the proportional distribution of the number of deaths per region, according to gender and age group.

Additionally, the data were analyzed and expressed by descriptive statistics, with absolute and relative frequency distribution. This study uses secondary data from GBD – a tool that stores health information from around the world – and is free from identification and rights of use. Thus, it was not necessary to submit the study to the Research Ethics Committee (CEP) involving human beings, as mentioned in Resolution No. 510/2016 of the National Health Council.

RESULTS

The mortality rate for CKD secondary to hypertension showed an increase over the years and in a heterogeneous manner among all units of the Brazilian federation (Figure 1). Among the States, in 1990, Paraíba led with a rate of 3.2 deaths per 100,000 inhabitants, followed by Rio de Janeiro and Minas Gerais, with 2.91 and 2.88, respectively. From 1996, Rio de Janeiro surpassed Paraíba and came to occupy first place, with the mortality rate estimated at 3.79 in the following years. The most recent data available – 2019 – shows the State of Rio de Janeiro with the highest mortality rates. In 2019, the states of Rio de Janeiro, Rio Grande do Sul, and Paraíba recorded the highest mortality rates: 7.44, 6.65, and 5.97, respectively.

Table 1 shows the comparison of the mortality rate of CKD due to hypertension in Brazil, between 1990 and 2019. For all age groups and both sexes, it is possible to observe the increase in the mortality rate in the country. In 1990, the mortality rate per 100,000 inhabitants was 2.41 deaths; whereas in 2019, the estimate was 5.38.

Regarding the average estimate of the number of deaths due to CKD secondary to hypertension in the studied period, we observed that in all units of the federation there was an increase in the number of deaths (Table 2). In the North region, the state of Pará had the highest values for both years: 93, in 1990, and 345, in 2019. In the Northeast, the state of Bahia had the highest number of deaths, with 296, in 1990, and 937, in 2019; followed by the state of Pernambuco: 183 and 511, in 1990 and 2019, respectively. In the Midwest region, the state of Goiás had 93 deaths, in 1990, and 363 deaths, in 2019, making it the State with the highest number of deaths. In the South and Southeast regions, the highest numbers of deaths were observed in the states of São Paulo and Rio Grande do Sul – São Paulo with 809, in 1990, and 2,486, in 2019; and Rio Grande do Sul with 242, in 1990, and 751, in 2019. We identified an increase in the number of mortality in all regions, with the Southeast region presenting the highest percentage – 1,684 (47.24%), in 1990, and 5,313 (45.55%), in 2019 – followed by the Northeast region, with 1,020 (28.78%), in 1990, and 3,199 (27.43%), in 2019 (Table 3).

Regarding the distribution of mortality by sex, we found that mortality was higher among males for both years, with a proportional distribution of 53.2%, in 1990, and 50.6%, in 2019. Thus, we can observe that there was a reduction in the difference in the number of deaths between the sexes (Table 4).

According to the deaths distributed by age group, the highest number was observed among individuals in the age group of ≥70 years, with 2,045 and 8,123 deaths, in 1990 and 2019, respectively. Followed by the age range of 50 to 69, with 1,211 deaths, in 1990, and 3,152, in 2019. In the range of 5 to 14, for both years, no death was identified by the disease (Graph 1).

DISCUSSION

CKD affects, approximately, 10% of the world’s population and every year there has been an increase in the prevalence of CKD, both in Brazil and worldwide. The development of the disease is mainly related to diseases such as diabetes and SAH.^12,13 Accordingly, this study showed, indirectly, that the prevalence of CKD in Brazil has been increasing, since the mortality rate showed a significant increase in all federative units, between 1990 and 2019 (Figure 1). This increase can be explained by the high prevalence of nocturnal hypertension, a resistant and uncontrolled asymptomatic hypertension, which causes long-term hypertensive nephroangiosclerosis.¹⁴

Kidney disease, in many cases, is asymptomatic or oligosymptomatic, expressing signs only when progressing to further stages of severity, which makes early diagnosis difficult.¹⁵ A study conducted with hypertensive patients in the state of Santa Catarina pointed out that 45% of these patients surveyed already had stage 2 CKD, which shows the importance of early detection of the disease for a proper management focused on its control.¹⁵ An important parameter used for the detection, evaluation, treatment, and prognosis of CKD is the glomerular filtration rate (GFR), since it helps to understand the number of functional nephrons.¹⁶

CKD can be defined by the presence of the following factors: sustained reduction of GFR below 60 mL/min/1.73m.; proteinuria, with presence of albumin in urine ≥30 mg for 24 hours; abnormalities in urinary sediment; hematuria; or a histology suggestive of injury.^5,6

According to the results of this research, the mortality rate and the overall number of deaths due to CKD increased in Brazil. This finding is similar to that seen in another study that revealed a growth in the number of patients of the Unified Health System (SUS) with CKD, undergoing dialysis treatment, along with high numbers of deaths from treatment abandonment.¹³ The results are also in agreement with the increase in prevalence and death from CKD in other parts of the world.¹⁷

Regarding the regions of the country, the Southeast region had the highest mortality rates due to CKD, followed by the Northeast region. A study that analyzed the situation of CKD in Brazil found that the highest prevalence of CKD was in the Southeast and Northeast region of Brazil, which can be explained by the high population density of these regions. Additionally, the high rates of death in the region can also be explained by the process of population aging, the epidemiological and demographic transition, and the increase in diseases such as SAH.^18,19

Mortality due to CKD secondary to SAH in males was higher than in females for all the analyzed years. Similarly, a previous study evaluating patients treated in a hemodialysis service showed that men are the most affected by CKD due to hypertension than women, as shown in another study that observed that men had higher blood pressure values, lower GFR, and higher serum creatinine levels in relation to women, suggesting a greater risk.²⁰ Older women, however, presented events contrary to those observed in younger women, a relationship that did not occur in the analysis among men. This shows that differences in gender and age should be considered.^21-23 Such differences are possibly related to the protective effects of estrogen in women and/or the deleterious effects of testosterone in association with bad life habits in men, which causes a faster decrease in GFR in the male population.²⁴

Regarding age groups, the vast majority of deaths were observed at ages above 50 years, specially in patients over 70 years of age, which corroborates other studies that showed that the highest mortality rate due to CKD was present in the age group above 60 years.²⁵ Moreover, it was observed that individuals aged 45 years are among the most prevalent population in dialysis treatment centers^7-8.

In this sense, aging is an important risk factor, since, in this process, events such as arteriosclerosis with concomitant progressive loss of renal function, evidenced by the reduction of GFR with advancing age, may further compromise renal function in the presence of diseases such as SAH, which presents itself as one of the most prevalent diseases in the elderly, generating direct stress on the renal system.²⁶

In the context of the detection and prevention of CKD and SAH, primary health care stands out as an important measure, which, with programs such as HiperDia, can perform follow-up and request tests during consultations, in order to identify and reduce early diseases related to SAH and diabetes, which are the main risk factors for the development of CKD.²⁷

Annually, billions of money is directed to the treatment of CKD patients worldwide, which generates a direct impact on the economy and local development of countries, showing the importance of prevention strategies for the main risk factors for CKD, such as SAH, as well as a timely diagnosis.²⁸

This study has limitations, regarding not only those inherent to the Global Burden of Disease Study but also those of the data sources, which depend on the accuracy with which the underlying cause of death is attributed, which can be complicated when multimorbidities are present. Nonetheless, this study showed the importance of describing mortality from CKD secondary to hypertension in Brazil, and may, in the future, support not only new policies but also comparative and intervention studies that monitor the transitions in trends of prevalence, incidence, and mortality of SAH and CKD.

With this study, we observed that the burden of CKD in Brazil increased in the last 30 years along with its mortality, which increased in all regions and federative units of the country; the Southeast being the region with the highest estimates of deaths in all years analyzed. Mortality was mainly higher among males but showed a tendency toward the inversion of this reality. Regarding the age group, deaths were higher in individuals over 70 years of age.

Thus, with SAH being an important risk factor for the development of CKD, we would like to draw attention to strategies and efforts aimed at the early identification and prevention of the disease, in concomitance with the strengthening of strategies for early detection of CKD, so that adequate management and treatment is carried out in a timely manner, in order to mitigate the risk of evolution to the terminal stage of the disease.

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