Abstract
In 2022, excess mortality in Spain was the third highest on record, surpassed only by 2020 and 2015. However, only 23% of this excess has been directly attributed to extreme heat. A key limitation of this estimate is that it is based on models that may suffer from biases and methodological constraints.
To address this issue, we aimed to estimate the excess mortality attributable to extreme temperatures in Catalonia during the summer of 2022. Additionally, we assessed how the risk of death associated with extreme heat may be modified by other factors, with particular attention to socioeconomic variables.
We employed a longitudinal ecological study design covering the period from 2015 to 2022, using data aggregated at the health-area level. Generalized linear mixed models were applied for the total population and separately for individuals aged 65 years and older. These models corrected for potential biases by using small-scale geographic units and explicitly accounting for spatial variability.
Our results indicate that during the summer months of 2022, 49.41% of excess mortality was attributable to extreme heat. Both heatwaves and extreme maximum temperatures significantly increased the risk of death.
Several effect modifiers were identified as factors that further increased mortality risk on days with extreme heat. These included being 65 years of age or older, high relative humidity, extreme minimum temperatures, and low income.
Based on our findings, we propose several methodological considerations for future research: (i) minimizing exposure misclassification by using smaller geographic units than those commonly employed in similar studies; (ii) explicitly accounting for spatial variability through approaches such as hierarchical Bayesian spatiotemporal models; and (iii) controlling for both spatial and temporal dependencies.