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Conteúdo (article):

Internações por Condições Sensíveis à Atenção Primária no Brasil no período de 2000 a 2022: tendências e desafios
Hospitalizations for Ambulatory Care-Sensitive Conditions in Brazil from 2000 to 2022: Trends and Challenges
Hospitalizaciones por Condiciones Sensibles a la Atención Primaria en Brasil en el período de 2000 a 2022: tendencias y desafíos
Autores: Suelen Carlos de Oliveira (ENSP/Fiocruz; Unigranrio) – e-mail: suelen.c.oliveira@gmail.com – https://orcid.org/0000-0002-0090-2341
Lucia de Fátima Nascimento de Queiroz (Consultora independente) – e-mail: lfnqueiroz@gmail.com - ORCID: https://orcid.org/0000-0002-2244-349X
Carla Lourenço Tavares de Andrade (Ensp/Fiocruz) – e-mail: carla.andrade@fiocruz.br – ORCID: https://orcid.org/0000-0003-3232-0917
Mariana Vercesi de Albuquerque (Ensp/Fiocruz) – e-mail: mariana.albuquerque@fiocruz.br – ORCID: https://orcid.org/0000-0002-0763-6357
Luciana Dias de Lima (Ensp/Fiocruz) – e-mail: luciana.dias@fiocruz.br – ORCID: https://orcid.org/0000-0002-0640-8387
Elzo Pereira Pinto Junior (Cidacs – Fiocruz-BA) – e-mail: elzo.junior@fiocruz.br – ORCID: https://orcid.org/0000-0002-6977-2071
Roberta Gondim de Oliveira (Ensp/Fiocruz) – e-mail: roberta.gondim@fiocruz.br – ORCID: https://orcid.org/0000-0001-8408-6427
Eduarda Ferreira dos Anjos (Cidacs – Fiocruz – BA/ Ensp/Fiocruz) – e-mail: eduarda.anjos@fiocruz.br – ORCID: https://orcid.org/0000-0003-4322-236X
Ligia Regina Franco Sansigolo Kerr (UFC) – e-mail: ligiakerr@gmail.com - ORCID: https://orcid.org/0000-0003-4941-408X
Cristiani Vieira Machado (Ensp/Fiocruz) – e-mail: cristiani.machado@fiocruz.br – ORCID: https://orcid.org/0000-0002-9577-0301

Resumo: Analisou-se a evolução das Internações por Condições Sensíveis à Atenção Primária (ICSAP) no Brasil de 2000 a 2022, destacando tendências nacionais e impactos da COVID-19. Estudo ecológico e longitudinal com dados do Sistema de Informações Hospitalares do SUS. Foram examinadas as taxas de ICSAP e sua proporção no total de internações, considerando população estimada, distribuição regional, estadual e faixas etárias. As 56.308.152 ICSAP registradas no período corresponderam a 20,8% das internações no país. Houve redução da taxa de ICSAP por 10.000 habitantes e da proporção total de internações, com estagnação entre 2015-2019. A maioria dos estados e regiões obtiveram redução, com maior decréscimo em estados do Norte, Nordeste e Centro-Oeste. Quanto aos grupos etários, verificou-se redução de ICSAP no período, com aumento na pandemia nos grupos mais vulneráveis, além de mudanças no padrão de causas. Durante a pandemia, houve redução das taxas entre 2020-2021, que se elevaram novamente em 2022. Ressalta-se a importância de políticas que garantam acesso integral e contínuo à Estratégia de Saúde da Família, especialmente para grupos vulneráveis, além da necessidade de investimentos contínuos para conter interrupções na atenção e reduzir internações evitáveis.
Palavras-chave: Condições sensíveis à atenção primária, Estratégia Saúde da Família, Sistema Único de Saúde, Brasil.

Abstract: The present study analyzed the evolution of hospitalizations for Ambulatory Care-Sensitive Conditions (ACSC) in Brazil from 2000 to 2022, highlighting national trends and the impact of COVID-19. This work is an ecological and longitudinal study, using data from the Hospital Information System (SIM) of the Brazilian Unified Health System (SUS). This study analyzed ACSC rates and their proportion of total hospitalizations, considering an estimated population, regional and state distribution, and age ranges. A total of 56,308,152 ACSCs were recorded during the period, corresponding to 20.8% of all hospitalizations in the country. A decrease was found in ACSC rates per 10,000 inhabitants and in the proportion of total hospitalizations, with stagnation observed between 2015-2019. Most states and regions saw a decline, with the largest decreases found in the North, Northeast, and Midwest regions. Regarding age ranges, a decrease in ACSC was observed during the period, with an increase during the pandemic among the most vulnerable groups, along with changes in cause patterns. During the pandemic, rates decreased between 2020-2021, only to rise again in 2022. The importance of policies ensuring comprehensive and continuous access to the Family Health Strategy (FHS) in Brazil is highlighted, especially for vulnerable groups, as is the need for continuous investments to prevent disruptions in care and reduce avoidable hospitalizations.
Keywords: Ambulatory care-sensitive conditions, Family Health Strategy, Brazilian Unified Health System, Brazil.
Resumen: Se analizó la evolución de las Hospitalizaciones por Condiciones Sensibles a la Atención Ambulatoria (HCSAA) en Brasil de 2000 a 2022, destacando tendencias nacionales e impactos de la COVID-19. Se trata de un estudio ecológico y longitudinal con datos del Sistema de Información Hospitalaria del SUS. Se examinaron las tasas de HCSAA y su proporción en el total de hospitalizaciones, considerando la población estimada, la distribución regional y estatal, así como los grupos etarios. Las 56.308.152 HCSAA registradas en el período representaron el 20,8% de las hospitalizaciones en el país. Hubo una reducción en la tasa de HCSAA por 10.000 habitantes y en la proporción total de hospitalizaciones, con estancamiento entre 2015-2019. La mayoría de los estados y regiones presentaron reducciones, con mayor disminución en los estados del Norte, Nordeste y Centro-Oeste. En cuanto a los grupos etarios, se observó una reducción de HCSAA en el período, con un aumento durante la pandemia en los grupos más vulnerables, además de cambios en el patrón de causas. Durante la pandemia, las tasas disminuyeron entre 2020-2021, pero volvieron a aumentar en 2022. Se destaca la importancia de políticas que garanticen el acceso integral y continuo a la Estrategia de Salud de la Familia, especialmente para los grupos vulnerables, además de la necesidad de inversiones continuas para evitar interrupciones en la atención y reducir hospitalizaciones evitables.
Palabras clave: Condiciones Sensibles a la Atención Ambulatoria, Estrategia de Salud de la Familia, Sistema Único de Salud, Brasil.
 
Introduction
The organization of Primary Health Care (PHC) services in Brazil has a historical trajectory marked by advances and setbacks over time. The creation of the Family Health Program (Programa Saúde da Família – PSF) in 1994, which later became the Family Health Strategy (FHS), is a milestone for PHC and the Unified Health System (SUS).
In the following decades, the ESF became a priority on the federal health agenda1,2 due to its relevance in expanding access, changing the care model, and financing SUS3,4. The priority nature of this strategy was also expressed in initiatives to train professionals, encourage research, and innovate in evaluation.
PHC evaluation initiatives, by governments or researchers in the country, were based on expert recommendations5,6 and experiences from other health systems. Evaluation methodologies focus on the structure and organization of the system, access, and quality of health care7-10. In addition to using direct indicators, such as vaccination coverage and lifestyle changes, these employed indirect indicators, including hospitalizations for PHC – Ambulatory Care-Sensitive Conditions (ACSC).
ACSCs are those for which high-quality primary care – "first-contact, accessible, continuous, comprehensive, and coordinated," as defined by the World Health Organization (WHO) – can prevent hospitalization, or in which early intervention can prevent complications or severity11. Indicators related to ACSCs have been used in other countries, sometimes referred to as "hospitalizations for ambulatory care-sensitive conditions (ACSC)" or "avoidable hospitalizations"11-17, including during the period of the COVID-10 pandemic18,19.
In 2008, the Brazilian Ministry of Health established a list of ACSCs20, consisting of nineteen groups of diseases whose hospitalizations could be prevented or diminished by high-quality, timely, and qualified ACSC21. Since then, Hospitalizations for ACSC have been used in SUS monitoring and evaluation studies, aiming to analyze PHC performance and improve health system management9, 22-27.
Comparative research on the adequacy of the indicator to analyze the effectiveness of PHC, as well as the results achieved in different socioeconomic contexts and health system configurations, has represented a fruitful field of study. It is important to note that the resolution capacity of PHC varies regionally, statewide, and municipally within SUS itself, highlighting the importance of observing the diversity of ACSCs within these distinct contexts.
Although there are numerous studies on hospitalizations for ACSCs of various scopes, there is a scarcity of national and longitudinal research covering longer periods. Furthermore, beginning in 2020, the COVID-19 pandemic changed the pattern of hospitalizations in the country, suspending elective care and shifting the system toward combating the health emergency. The changes in the number and severity of hospitalizations, with different patterns across age ranges and regions, highlighted the need to analyze how ACSCs behaved in this context. Among the publications on the topic, this study stands out for its long period of analysis (2000 to 2022) and for its identification of variations in the magnitude of rates and the pace of admissions throughout both regions and states, in addition to highlighting the age ranges most likely to benefit from specific measures.
The questions guiding the study were: What was the evolution of ACSCs in Brazil between 2000 and 2022? How was this evolution affected by the COVID-19 pandemic?
The present study aimed to (i) analyze the evolution of ACSC in Brazil in a time series of more than two decades, from 2000 to 2022, and (ii) identify national trends and the repercussions of the COVID-19 pandemic.

Methods
This work presents an ecological, longitudinal, descriptive study, conducted using publicly available, unrestricted secondary data extracted from the reduced databases of hospital admission authorizations (Autorizações de Internações Hospitalares – AIH) from the SUS Hospital Admissions System (Sistema de Internações Hospitalares do SUS – SIH-SUS) of the Ministry of Health (MoH). Hospitalization data from 2000 to 2022 in Brazil were collected monthly and organized annually and by state, highlighting the effects of the COVID-19 pandemic. Data for 2022 were accessed in January 2024. The databases were manipulated using SAS, version 9.4, software, and graphs were constructed in Excel.
The evolution of hospitalization rates for ACSCs per 10,000 inhabitants and the share of ACSCs in total hospitalizations were analyzed, considering the Brazilian population, estimated by the Brazilian Institute of Geography and Statistics (IBGE) as a whole, by regions and states, and by age ranges.
Data analysis on causes of hospitalization was performed for the 19 diagnostic groups that make up the ACSCs within all age groups. Regarding prenatal and childbirth-related illnesses, our study considered complications affecting pregnant and postpartum women that could have been prevented with quality primary care.
The six main causes of hospitalizations at the beginning and end of the study period were highlighted for the population under five and over sixty years of age, based on the relevance of ACSCs in these age groups, both in terms of rate and proportion of hospitalizations.
The estimated or potential coverage indicators for the FHS and PHC were obtained from the MoH website. On the webpage, accessed in May 2023 (https://sisaps.saude.gov.br/painelsaps/saude-familia), PHC coverage was available for the years 2007 to 2022, and FHS coverage from 2007 to 2020. Given changes in funding that required the registration of the covered population, the MoH adopted the term "potential coverage" for the purposes of comparability of the series28. The potential coverage of Family Health Teams (FHTs) was estimated, considering the number of teams and the recommended population coverage per team (3,500 people) in relation to the total population. The formula used by the MoH in 2022 was:

Estimated or potential coverage of FHT = (in FHT x 3500) x 100 / IBGE population estimate

The second indicator considers the estimated potential coverage of all PHC services recognized by the MoH, taking into account FHTs or PHC teams with configurations that are distinctly from the FHS, including teams working in Street Clinics (FHT-SC), with the riverside population (FHT-RP) or the prison population (FHT-PP):

Estimated or potential coverage of PHC team = (in FHT x 3500) + (in PHC team 20 h x 1750) + (in PHC team 30 h x 2625) + (SISAB population of FHT-SC, FHT-RP and FHT-PP*) X 100/ IBGE population estimate

The FHS\'s estimated population coverage data from 2000 to 2006 were no longer available online, but they had been obtained from the MoH website in May 2017 and were included in the research group\'s archives. At that time, the MoH also estimated coverage based on the number of funded teams and the recommended population coverage per team, which was approximately 3,500 people.
Because this study used secondary, publicly accessible data with de-identified information, the research was not submitted to a Human Research Ethics Committee.
Results
Between 2000 and 2022, 56,308,152 hospitalizations for PHC-sensitive conditions were recorded in Brazil, corresponding to 20.8% of the 270,855,504 total hospitalizations. These hospitalizations cost SUS approximately R$39,539,942,995 and R$258,654,667,294.76, respectively, with an average cost of R$751.93 for hospitalizations due to ACSCs and R$959.43 for general hospitalizations.
Between the first and last years analyzed, the hospitalizations due to ACSC (HACSC) rate decreased from 174.1 to 93.7 per 10,000 inhabitants (Figure 1), and the proportion of total hospitalizations decreased from 24.3% to 16.1% (data not shown). The rate of decline varied over time. The decrease in HACSC cases until 2019 accompanied the increase in FHS coverage (Figure 1). A downward trend was observed in the HACSC rate per 10,000 inhabitants between 2000 and 2008, when FHS expansion was observed, followed by a small increase between 2008 and 2010, a further decrease between 2010 and 2016, and stagnation between 2016 and 2019. Between 2020 and 2021, the first two years in which the country was most affected by the COVID-19 pandemic, the rates reached their lowest levels. The monthly analysis (data not shown) showed a decrease, beginning in March 2020, the month in which COVID-19 hospitalizations began to increase. In 2022, the rate rose again, remaining below the 2019 level.

Figure 1
Decrease in ACSC between 2000 and 2022 occurred in all regions of the country, following the national trend, with differences in rates of decline between regions and state (Table 1).

Table 1
In 2000, the South region presented the highest rate (225.1), followed by the Midwest (210.2), Northeast (186.1), North (184.1), and Southeast (141.2) regions. In 2022, the South region had the highest rate of ACSC per 10,000 inhabitants (112.6), despite a negative variation of 50%, representing the second largest decrease among the regions during the period studied. The lowest rate was in the Southeast (86.7), also with the smallest percentage in decline (-38.6). The North, Northeast, and Midwest had, respectively, rates of 98.4, 94.3, and 89.3 per 10,000 inhabitants. The states with the highest rates of HACSCs per 10,000 inhabitants, by year analyzed, were: Rondônia in 2000 (303.8%), Piauí in 2009 (225.9%), and Maranhão from 2019 to 2022, all three of which are located in the North and Northeast regions of Brazil.
The variation in the ACSC rate from 2000 to 2022 was negative in most states and in all regions of the country. The largest decreases occurred in Paraíba (-68.2%), Goiás (-66.0%), Alagoas (-65.3%), Mato Grosso (-63.1%), Tocantins (-62.6%), Rio Grande do Norte (-61.6%), and Rondônia (-60.8%). The states with the largest decreases are in the North, Northeast, and Midwest regions. Only Amazonas (27.7) and Roraima (189.3) showed an increase during the period.
Between 2020 and 2021, when the non-pharmaceutical measures (masks and social distancing in 2020-21) and pharmaceutical measures (vaccination in 2021) recommended to control the COVID-19 pandemic were implemented in the country, the national rate of hospitalizations for ACSCs per 10,000 inhabitants decreased by -1.4%, followed by a 23.5% increase in 2022.
Although declines in ACSCs were observed for all age ranges between 2000 and 2022, there were variations among them. The age ranges with the highest rates of HACSCs were among the elderly, over 80 years of age; the elderly, aged 60 to 79 years, and children, aged 0 to 4 years. In these three age ranges, the downward trend in ACSCs was most evident, in terms of the population rate per 10,000 inhabitants (Figure 2). Among those over sixty, there was a continuous decrease between 2000 and 2007, with a sharp decline between 2007 and 2008 and between 2019 and 2020, in the latter case in the context of increased hospitalizations due to COVID-19. However, between 2020 and 2021, rates rose again for the three most sensitive age ranges (over 80, 60 to 79, and children aged 0 to 4).

Figure 2
An analysis of HACSCs by cause, considering the age ranges of children under five and the elderly, shows significant changes during the period.
Between 2000 and 2022, among the six main causes of ACSCs among children under five, hospitalizations due to infectious gastroenteritis and its complications decreased (from 172.6 to 41.5 per 10,000 inhabitants) and hospitalizations due to asthma (from 89.8 to 24.3 per 10,000 population). Hospitalizations due to lung diseases increased from 21.5 to 61.5 per 10,000 inhabitants; hospitalizations due to bacterial pneumonia increased from 16.4 to 36.4 per 10,000 inhabitants; due to kidney and urinary tract infections rose from 7.5 to 14.2/10,000 inhabitants; and those caused by diseases related to prenatal care and childbirth rose from 1.5 to 15.3/10,000 inhabitants (Figure 3).

Figure 3
Among the elderly population (over sixty years of age), there was also a decrease in HACSC rates for most causes between 2000 and 2022 (Figure 4), although HACSC rates remained higher in this age group than in others and showed changes in the composition of the most frequent causes.
In 2000, the six leading causes of HACSC per 10,000 inhabitants in the population of over sixty years of age were: heart failure (195.9), lung disease (129.4), cerebrovascular disease (101.5), infectious gastroenteritis and its complications (52.6), hypertension (48.7), and diabetes mellitus (43.8). In 2022, the main causes of HACSC in this population group, per 10,000 inhabitants, were cerebrovascular diseases (56.7), followed by heart failure (51.8), kidney and urinary tract infections (32.2), lung diseases (24.7), diabetes mellitus (22.4), and angina (20.5). It is important to highlight the increase in the rate of kidney and urinary tract infections, which is the only one, among the six most frequent causes of hospitalization, to increase in the period for this age range, from 20.2 in 2000 to 32.2 per 10,000 inhabitants in 2022.

Figure 4
Discussion
The downward trend in HACSC in Brazil between 2000 and 2022 identified in this study corroborated the results of previous national longitudinal studies9,22,29-33, highlighting the sharp decrease recorded in the initial period of the analysis, between 2000 and 2008. Several studies have pointed to a negative correlation between HACSC and the expansion of the FHS in the country, reflecting efforts to strengthen PHC within SUS during this period, as well as the effectiveness of the FHS model in addressing health inequalities.
Previous research has explored the relationship between PHC and HACSC at the macroregional31,34, state23,30,35,36, and municipal24,37,38 levels; and/or analyzed these relationships across different age ranges7,25,34,39-41, with relevant contributions. The analysis by macroregion and state conducted in this study corroborates the conclusions of other studies, according to which structural inequalities and in the implementation of the FHS are driving the differences in declines in ACSC. Despite the high rates of ACSC per 10,000 inhabitants observed between 2000 and 2022 in the South region, the highest rates were concentrated in some states in the North and Northeast, while the largest declines were observed in states in the North, Northeast, and Midwest regions.
Municipal-based studies have been important in analyzing the relationship between health care configuration and HACSCs. Macinko et al.22 found that, from 1999 to 2007, greater PHC coverage was associated with lower rates HACSCs, while a greater presence of private beds was associated with higher rates of HACSCs22. Boing et al.42 and Castro et al.8 recognized the correlation between a greater availability of physicians in PHC services and a decrease in HACSCs. Castro et al.9 found that municipalities with lower PHC quality showed HACSC rates of 21.2% higher than did municipalities with the highest ratings in the Primary Care Quality Improvement Program (PMAQ-AB), even in socially vulnerable contexts.
In the state of Rio de Janeiro, Hone et al.30 found that each additional FHS visit was associated with a 3% lower rate of HACSCs, a 63% lower rate of 30-day readmissions for any non-congenital cause, and a 57% lower rate of 30-day readmissions for HACSCs. According to the authors, the elderly, those with less education, the unemployed, and those with higher incomes showed the greatest declines in HACSCs associated with the FHS30.
The situation in Rondônia stands out, as it recorded high rates of HACSCs per 10,000 inhabitants between 2000 and 2022. Freitas et al.43, analyzing ACSCs among children in the state, highlighted the low coverage of basic sanitation and a high proportion of pregnant women with fewer than six prenatal appointments. In this state, 42.8% of ACSCs were recorded among children under nine years of age, with higher ACSC rates recorded in smaller municipalities44. This indicates the need to expand access to health care for vulnerable groups, as well as coordinate public policies to improve living conditions.
In the analysis by age range and cause, among the population under five years of age, a notable decrease was observed in hospitalizations for infectious gastroenteritis and its complications. While the incidence of these infections can be diminished by access to safe water, basic sanitation, and preventive measures (food hygiene, rotavirus vaccination), in turn reducing hospitalizations due to these causes, depends on timely care in PHC for children with gastrointestinal symptoms (e.g., oral rehydration therapy, medications in appropriate cases). Santos et al.45 associated the decrease in hospitalizations of children due to gastroenteritis and other causes with factors such as planning by FHS teams, operations carried out during special hours, the existence of child care facilities in the units, and the availability of vaccines.
However, the study revealed an increase in hospitalizations for prenatal and childbirth-related illnesses in this age range, associated with congenital syphilis. Figueredo et al.46 reported macroregional variability in limitations on access to syphilis treatment in PHC, finding that penicillin administration is not a majority practice in a a great majority of municipalities in the Southeast and Northeast regions. A study on HACSCs in children under five years of age in Minas Gerais, between 2008 and 2018, found that congenital syphilis is related to social vulnerability and gaps in prenatal care47. Other studies have highlighted flaws in health system management, referral and counter-referral actions, integration between epidemiological surveillance and PHC actions, the institutionalization of continuing education programs, and basic care, including the administration of penicillin by PHC services48,49. The observed decline in HACSC in the population over sixty years of age was previously confirmed in national9,33,41 and regional23,26,30,50 studies. The main causes of HACSC among the elderly were circulatory system diseases; respiratory system diseases; and endocrine, metabolic, and nutritional disorders, with a 61.5% decrease in hospitalization rates for heart failure and a 27.3% increase in hospitalizations for pneumonia. It is important to note that, in this age range, there was an increase in kidney and urinary tract infections during the period, the relevance of which has been highlighted in previous studies26,50-52. Pinto et al.50 highlighted the following as important measures to prevent hospitalizations for this cause among the elderly: stratification by risk and vulnerability; longitudinal consultations; emphasis on self-care and home care; and collaboration between FHS teams and caregivers of elderly individuals to ensure ongoing care, such as regular fluid intake and pneumococcal immunization.
Another key comment concerns the intensity of the decline in HACSC rates at different points in time, with a slight slowdown observed between 2015 and 2019. Although the limitations of this study do not allow for inferences between the policies of successive governments and the evolution of HACSC, previous studies have raised hypotheses in this regard. Barros et al.38 found that fiscal austerity policies resulted in reduced PHC spending in municipalities with greater socioeconomic deprivation, particularly between 2015 and 2016. Santos et al.45 warned of a slower decline in HACSC rates between 2015 and 2019, a period of austerity and economic crisis in the country.
The diminished impact of the COVID-19 pandemic on HACSC behavior, observed in this study, has also been recorded in previous studies. Viola53 found reduced care and hospitalizations for various PHC-sensitive conditions in five cities (Manaus, Belo Horizonte, Recife, Brasília, and Florianópolis) from 2017 to 2021. Dalberto54 and Gama and Silva55 reported similar declines in HACSC, followed by upward trends, likely resulting from the accumulation of demand caused by restrictions imposed on the population during the most critical period of the pandemic. Further research is warranted to explore the factors behind this decline, which is not necessarily related to improved PHC, but rather to difficulties in accessing hospital services due to physical distancing, fear of contamination, and/or overloading of services with COVID-19 care.
In summary, the results of this study reinforce the merits of implementing policies focused on comprehensive and continuous care, such as the FHS model, along with investments in health promotion and prevention, in an attempt to reduce hospital admissions for conditions that could be treated in PHC51. Furthermore, the results also corroborate the assertion that, during health crises such as the COVID-19 pandemic, to avoid disruptions in health care, increased public funding and the adoption of adaptive strategies in the planning and delivery of health services are necessary56,18,19.
The limitations of using the ACSC indicator have been highlighted in previous studies, which highlighted an underreporting of hospitalizations, inaccuracies in diagnostic classification, and limited coverage of the ACSC index51. These factors highlight the need for improved health data recording. In the data on FHS and PHC coverage, any fluctuations that may be related to changes in calculation criteria established by the MoH did not compromise the analysis of the overall trend. Despite the mandatory collection and recording of race/color information in the SUS Information Systems since 2017, the improvement in the quality of its completion in hospital information systems has been recent and gradual; the absence of this information represented 35.4% of all hospitalizations in 2008, falling to 23.3% of all hospitalizations and 22.4% of all HACSCs in 2021, with significant territorial variation57. The gaps in this information hindered the analysis of ethnic-racial inequalities in access to and use of services, along with health outcomes during the study period. The prospect of improved recording quality after the elimination of the "no information" option for the race/color information reinforced the importance of conducting studies that explore this important dimension of Brazilian inequality.
This study was limited by its descriptive nature, the analytical omission of bed availability, and its focus on national rates, which failed to provide in-depth explanations for the causes of changes in HACSCs during the period, as well as the persistence of spatial and intergroup disparities. Further research is warranted to analyze the correlation of ACSCs with socioeconomic (income, ethnic/racial), territorial (municipal), and regional inequalities; in bed availability (considering public-private composition); and with health system characteristics (management, organization, and care), including records during the COVID-19 pandemic.
Regarding the use of ACSCs to assess the health system, despite the limitations identified in the literature, their importance is associated with their magnitude, as they accounted for over 20% of all hospitalizations in the country during the period analyzed in this study. This fact highlights the need to monitor ACSCs, as well as to carry out in-depth studies on the structure and effectiveness of PHC strategies, aiming to subsidize public policies to strengthen SUS and improve the health conditions of the Brazilian population.

Conclusion
This study found that the national rate of HACSCs in Brazil showed a continuous downward trend from 2000 to 2022. However, the following were observed: (i) variations in the magnitude of the rates and the pace of decline across regions and states; (ii) a greater decline in rates at the extremes of life, that is, in the age ranges under five and over sixty; (iii) differing behavior within the various cause groups, with a decline in hospitalizations for some causes and a worrisome increase in hospitalizations for others; and (iv) the effects of the COVID-19 pandemic on HACSCs, with a decrease in 2020 and 2021 and an increase in 2022 to levels below those of 2019.
The decrease in HACSC rates during this period occurred in a context marked by expanded access to PHC in Brazil. However, the decline did not occur at the same pace at different points in time, nor in the same manner throughout regions, age ranges, or causes.
The increase in hospitalizations due to prenatal and childbirth-related illnesses in children under five years of age, and in hospitalizations due to kidney and urinary tract infections among the elderly, highlighted gaps in organization and care in PHC that urgently need to be addressed in order to reduce morbidity from preventable conditions that can lead to complications, sequelae, and death.

Acknowledgements
We are grateful for the financial support from the NIHR/SEDHI Global Health Research Unit and for their contributions to the project\'s discussions.
CVM and LDL are CNPq Research Productivity Fellows and FAPERJ Scientists of Our State.

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