Excess of mortality in Catalonia during the summer of 2022 was related with high temperatures

The first seventeen days of July 2023 placed this month as the third warmest in the historical series in Spain, behind only 2022 and 2015 (AEMET).

Regarding last summer, a joint effort of the Catalan Health Department, the Catalan Health Institute and researchers of the Department of Physics of the UPC has shown than the main cause of the excess mortality occurred during summer 2022 in Catalonia was the high observed temperatures and not the diagnosis of influence like illness (mainly COVID-19).

They performed a retrospective study using publicly available data of meteorological variables, influenza-like illness (ILI) cases (including COVID-19) and deaths. They compare the curves of mortality, ILI and temperature analyzing the observed lag between the curves and calculating the correlation between them.

During the summer of 2022 17,551 deaths were reported in Catalonia. The observed lag and the correlation between the z-scores of temperature and all-cause deaths was 3 days and R² = 0.86, while between ILI and all-cause deaths was 22 days and R² = 0.21 (correlation closer to 1 means higher relation between the variables). This high correlation between temperature and deaths increased up to 0.91 when we excluded those deaths reported as COVID-19 deaths, while the correlation between ILI and non-COVID-19 deaths decreased to −0.19. No correlation was observed between non-COVID deaths and temperature or ILI cases in 2021.

Our study suggests that the main cause of the increase in deaths during summer 2022 in Catalonia was the high temperatures and its duration. The contribution of the COVID-19 seems to be limited.