Más allá de los mapas temáticos: la armonización de unidades estadísticas y sanitarias para visualizar los determinantes sociales de la salud

An inclusive research group is said to be that group of researchers that does not discriminate against its own because of their background or their training in the past. This entry is worth it for the EvaluAES group to obtain the accreditation of an inclusive group, with a physicist and a geographer presenting and commenting on health evaluation things in the past XIV EvaluAES Workshop. Santiago Royo Sierra (Aragonese Institute of Health Sciences, IACS) and Olga de Cos Guerra (University of Cantabria) deploy and discuss a promising tool to apply in the evaluation of health policies and services.

And if you don’t want it, the EvaluAES group would like to remind you that this principle of the Universal Declaration of the Rights of the Researcher, without distinction of race, sex, religion, nationality, backgroundopinion or any other personal or social condition or circumstance, remains in force in the call for abstracts of the next XV EvaluAES Workshop, which remains open until November 17. We do not know if in 2026 we will advance the clocks once again, but what we have advanced is the XV EvaluAES Workshop, which will be held next year on February 6 at the University of Granada.

Job summary (Santiago Royo-Sierra)

In health services research, it is essential to understand how social and socioeconomic determinants influence population health and health system performance. However, part of the information needed to understand this relationship, which refers to the socioeconomic situation of the reference population of the National Health System (SNS), is referred to at the level of administrative area and not health area. This is because healthcare is organized territorially based on the population assigned to a Primary Care team, and the reference limits of these teams do not have to be subject to territorial administrative limits. That is, a Basic Health Zone (ZBS), the minimum reference unit of the SNS, can cover several municipalities or refer only to a neighborhood or a part of a neighborhood, depending on the characteristics of the population (ie, age, sex, population density, rurality, geographical dispersion of urban centers, etc.)

The National Institute of Statistics (INE) systematically collects a multitude of socioeconomic data, characterizing the population at the census section level (minimum administrative territorial unit of reference), which could be reused to approximate the measurement of the social determinants of health and contextualize the evaluation of the performance of health services. Initiatives such as Mortality in small areas of cities in Spain and Socio-Economic and Environmental Inequalities (AVERAGE) have recognized the value of this information to evaluate the health status of the population, proposing the calculation of a deprivation index at the municipal level for the entire Spanish population. This socioeconomic information—whether in the form of a synthetic index or as independent variables of income level, educational level, etc.—is of special interest for the evaluation of equity of access to the health system and for the evaluation of the performance of health services. The problem posed by the reuse of this information is the incompatibility of its geographic reference units. The INE publishes its data at the census section level, while the management of Primary Care in Spain is articulated around the ZBS. This geographical misalignment (Figure 1), an issue studied in depth in the area of ​​geostatistics and described in the article by Zhukov et al. (2023)prevented the direct connection of both sources of information, a challenge that our recent job in Gaceta Sanitaria tries to overcome.

Figure 1. Real example of misalignment between census tract (red area-INE map) and basic health zone (gray area-VPM Atlas map).

The Solution: A Robust Method for Data Mapping

Our study proposed a rigorous method to reconstruct the ZBS from the INE census sections. The process, which is detailed in the article product of this jobinvolved the alignment, assignment and integration of more than 36,000 census sections in the 2405 ZBS of the Spanish territory through 7 steps, using the INE digital maps 2022 and Atlas Variations in Medical Practice (VPM) 2018. Thus, we convert each polygon of each census section into a point (centroid) to assign them to each ZBS in a census section to ZBS ratio of N:1. Next, we validate this assignment with a minimum of 95% of the area of ​​the section contained in the ZBS (Figure 2) and reconstruct the new limits of the ZBS from the limits of the census sections assigned to it (Figure 3).

Figure 2. Real example of a census section (red area-INE map) assigned to basic health zone (gray area-VPM Atlas map) exceeding 95% of the area threshold.

Figure 3. Real example of the reconstruction of the new limits of a basic health area (right) from the limits of the census sections (left).INE map) that have been assigned to you.

The key to the success of the method was its high efficiency: the programmatic assignment managed to locate 99.7% of the census tracts automatically (only ten census tracts required manual assignment), with more than 93% of them exceeding the overlap threshold of 95% of the area.

To validate the process of assigning census section to ZBS, we verified that the distribution of individual net income among the ZBS reconstructed from the census sections was consistent with the original distribution. To illustrate these results, we show the quintiles of average net income (€) per capita in the new ZBS map of the SNS (Figure 4).

Figure 4. Distribution (quintiles) of the average net income per capita by basic health zones (ZBS) for the National Health System in Spain in 2022. Source: Own elaboration based on data from the National Institute of Statistics. Household income distribution atlas.

Utility and implications for decision making.

The main contribution of this work is the creation of an analytical resource of great value for research and policy formulation. Integrating socioeconomic information into ZBS enables a new ability to model or adjust the influence of social determinants on the equity and efficiency of the health system.

This new map allows researchers to analyze and evaluate:

• The geographic variation in health and the use of health services in relation to the socioeconomic level of each area;
• The impact of the sociodemographic characteristics of the population on access to health services;
• The impact of health policies on reducing health inequalities.

Furthermore, the proposed method has been designed to be easily reproducible and adaptable to future updates of both census tract maps and ZBS. The code and materials. used are available under an open source license (CC-BY 4.0 International) in a GitHub repository, promoting transparency and collaboration in the scientific community.

In essence, this solution provides a robust and reliable method that systematically connects socioeconomic and health data, laying the foundation for more accurate research and more informed decision making. We hope that this resource encourages the inclusion of the large-scale socioeconomic perspective in health services research, contributing to system improvement and the promotion of equity. From this forum we encourage all readers to take a look at the repository and use the tools they provided for their future research in this area.

Santiago Royo Sierra (Aragonese Institute of Health Sciences, IACS), presenting their work at the last XIV EvaluAES Workshop in Santander.

Comments (Olga de Cos Guerra)

The aforementioned contribution represents a contribution of interest in four fundamental axes. The study stands out, first of all, for its methodological contribution, since the authors propose an automated, updateable and exportable methodological gateway for the assignment of statistical data referring to a census unit (section) that is transferred to the health management unit (ZBS). Secondly, this study represents a notable contribution if it is contextualized in the National Public Health Strategy (2022), which incorporates references to the importance of the social determinants of health for equity in health matters. Thus, the commented study presents points of convergence with the article by C. Bentué and I. Quílez (2023) where the authors harmonize sociodemographic data at the ZBS level, using a spatial overlap method to generate a synthetic index of social vulnerability for the elementary health management units of the Spanish autonomous communities.

Olga de Cos Guerra (University of Cantabria), commenting on the work in the past XIV EvaluAES Workshop in Santander.

At the same time, the challenge of health equity is often made difficult by the circumstances associated with demographic and social change, with populations experiencing an aging process that can lead to special needs in certain detailed areas (such as neighborhoods in urban centers). In this context, having harmonized census data at the health unit level opens important opportunities for sociodemographic analysis and diagnosis that can help prevention and resource management based on real needs with a multi-scalar perspective. In this way, another aspect of the aforementioned study is valued, which is its interest for prevention and management, in line with the concept of geoprevention to advance spatially differentiated strategies that contribute to the design of more effective actions (De Cos et al., 2021).

If research and transfer necessarily go hand in hand, and feed each other synergistically, this contribution – aligned with the opening of geographical data to society initiated with the INSPIRE Directive (2007/EC)– shares its harmonized cartographic database with the community under an open source license in the research group’s GitHub repository Data science for health policies and services. From this cartographic base, the community will be able to advance in the sociodemographic research of the health management units, integrating the layer in a geographic information systems (GIS) environment and launching the geoprocesses and spatial analysis operations for progress, based on what the aforementioned contribution provides.

Finally, it should be noted that this work was also presented at the XLIV AES Conference, held in June 2025 in Madrid, and won the award for best oral communication.

Santiago Royo Sierra being awarded for the best oral communication. XLIV AES Conference.