Regional Disparities in Stroke Hospitalization and Mortality Associated with Long-Term Fine Particulate Matter Exposure: A Nationwide Ecological Study in Spain.
Ramírez-Moreno J, Martín Hernández V, et al. • Medical sciences (Basel, Switzerland) • 2026
PM2.5 showed the largest positive ecological correlation with age-standardized stroke mortality rate among all pollutants examined (r = 0.264, p < 0.001), but overall pollutant-outcome correlations were weak and heterogeneous, and regional variation in stroke burden was not adequately explained by the available air-pollution indicators.
Key Findings
Results
PM2.5 showed the largest positive ecological correlation with age-standardized stroke mortality rate (ASMR) among all pollutants examined, though the correlation remained weak.
The correlation between PM2.5 and ASMR was r = 0.264, p < 0.001
Despite statistical significance, the correlation magnitude was characterized as 'weak' by the authors
This was the strongest association found among all pollutants examined in the study
Associations with hospitalization and other pollutants were described as 'small and inconsistent'
Results
There was marked regional variation in stroke hospitalization rates across Spain's 17 autonomous communities from 2013 to 2021.
Mean age-standardized hospitalization rate (ASHR) was 20.1 ± 5.4 per 10,000 population
The study covered Spain's 17 autonomous communities over the period 2013 to 2021
The dataset comprised 306 sex-specific region-year observations
Regional variation in stroke burden was not adequately explained by the available air-pollution indicators
Results
Overall ecological correlations between air pollutants and stroke outcomes were weak and heterogeneous in direction.
Pollutant-outcome correlations were described as 'weak and heterogeneous in direction'
Multiple stroke outcomes were assessed: age-standardized hospitalization rate (ASHR), crude hospitalization rate (CHR), crude mortality rate (CMR), age-standardized mortality rate (ASMR), case fatality rate (CFR), and in-hospital mortality index (IMI)
PM2.5 was weakly associated with ASMR, while associations with hospitalization metrics were small and inconsistent
No single pollutant demonstrated consistent, strong associations across multiple stroke outcomes
Methods
The study used an ecological design with aggregated data, limiting causal and individual-level inference.
The study was a 'nationwide longitudinal ecological study using aggregated stroke indicators'
Stroke data came from INCLASNS and air-pollution data from MITECO
Sex-stratified analyses were 'considered exploratory because pollutant concentrations were measured at the regional-year level and were not sex-specific'
Authors explicitly stated that 'these ecological findings do not support causal or individual-level inference and warrant confirmation using higher-resolution exposure and individual-level data'
Discussion
Regional variation in stroke burden in Spain was not adequately explained by the available air-pollution indicators alone.
The study examined multiple pollutants in relation to stroke outcomes across 17 autonomous communities
The authors concluded that 'regional variation in stroke burden was not adequately explained by the available air-pollution indicators'
This suggests other classical vascular risk factors and environmental determinants may play a larger role in explaining regional disparities
The authors noted 'considerable regional heterogeneity in incidence and mortality reflecting differences in classical vascular risk factors and environmental determinants'
What This Means
This research examined whether long-term exposure to air pollution—particularly fine particulate matter (PM2.5)—could explain regional differences in stroke hospitalizations and deaths across Spain's 17 regions between 2013 and 2021. Using publicly available national health and environmental data, researchers analyzed over 300 region-year data points and found that while PM2.5 had the strongest statistical link to stroke death rates among the pollutants studied, the association was still weak. Other pollutants showed even smaller and inconsistent relationships with stroke outcomes. The average stroke hospitalization rate was about 20 per 10,000 people, but this varied considerably across regions.
The study found that differences in air pollution levels between Spanish regions do not adequately account for the wide variation in stroke rates seen across the country. This suggests that other factors—such as differences in classical cardiovascular risk factors like high blood pressure, diabetes, obesity, or lifestyle factors—likely play a larger role in driving regional stroke disparities. The researchers also noted that because the study used regional averages rather than data from individual patients, it is not possible to draw conclusions about how air pollution affects any particular person's stroke risk.
This research suggests that future studies should use more detailed, individual-level data and finer-grained pollution measurements to better understand the relationship between air quality and stroke. At a public health level, the findings highlight that stroke prevention in Spain likely requires addressing a broad range of risk factors beyond air pollution, and that environmental policies alone may be insufficient to close regional gaps in stroke burden.
Ramírez-Moreno J, Martín Hernández V, Olivera A, Mata N, Hernández M, Sedas P, et al.. (2026). Regional Disparities in Stroke Hospitalization and Mortality Associated with Long-Term Fine Particulate Matter Exposure: A Nationwide Ecological Study in Spain.. Medical sciences (Basel, Switzerland). https://doi.org/10.3390/medsci14040475