In a recent study published in Nature Medicine, researchers estimate mortality due to heat in Europe in the summer of 2022, which was Europe’s hottest summer on record. To this end, epidemiological models were used to determine that 62,862 individuals died in Europe due to heat-related causes, which is the second highest in recorded history after the summer of 2003.
Study: Heat-related mortality in Europe during the summer of 2022. Image Credit: Eli Mordechai / Shutterstock.com
European summer heat
Greenhouse gas (GHG) emissions have resulted in significant global climatic change, which has increased the frequency of extreme weather events, including heatwaves and intense summers.
The last eight years have been the hottest globally, with 2022 being the fifth warmest year ever recorded. Europe remains one of the worst regions affected, with ambient temperatures an average of 1 °C warmer than before the industrial revolution.
Research predicting future climate has cautioned about the health implications of global warming. In fact, heat waves are associated with the worst morbidity and mortality impacts of any extreme weather event.
Europe experienced the worst heat wave in history in 2003 when 71,449 excess deaths were recorded between June and September. The consequential panic resulted in the rapid design and implementation of various strategies to protect high risk individuals, including the elderly, women, and socioeconomically disadvantaged. The effectiveness of these policies is contentious, with limited evidence favoring the strategies.
Europe experienced its hottest season on record in the summer of 2022. Intense heat waves resulted in droughts and fire across many regions, with Eurostat, the European statistical office, reporting unusually high mortality during the season. However, the entire European region has not yet quantified heat-related mortality.
About the study
In the present study, researchers utilize epidemiological models to quantify the mortality burden between May 30, 2022, and September 4, 2022. Moreover, the researchers elucidate age- and sex-specific heat risks and compare their findings with mortality reports from the summer of 2003.
Weekly all-cause mortality data was compiled and classified from Eurostat by sex and age. The final dataset comprised 21,913,050 male and 22,000,519 female deaths between January 2015 and November 2022. High-resolution temperature data was also acquired from ERA5-Land for model calibration.
Temperature and mortality data between January 2015 and December 2019 were used to calibrate epidemiological models, which were then used to estimate age- and sex-specific mortality for 2022. Statistical analyses comprised a quasi-Poisson regression model, which was used to evaluate temperature-mortality relationships in each of the 823 identified European regions.
Subsequently, a meta-regression analysis was performed using country, location-specific temperature average, temperature interquartile range, and proportion of citizens 80 years or older as predictors.
Study findings
Epidemiological models estimate that 62,862 people died due to heat-related complications in Europe in 2022. Of these, 61,672 individuals died between March 30, 2022, and September. 4, 2022. Countries near the Mediterranean Sea were the worst affected, with Italy, Greece, Spain, and Portugal reporting 295, 280, 237, and 211 deaths/million, respectively.
Age was a significant predictor of death, with significant increases in mortality observed with age. Individuals between ages 0-64, 65-79, and 80+ years comprised 4,822, 9,226, and 36,848 deaths, respectively.
Men had a 43% higher probability of mortality in the 0-64 age group; however, this trend was reversed in the 65-79 and 80+ cohorts, in which females had a 6% and 121% increased likelihood of mortality, respectively.
Temperature data revealed that Europe’s summer mean temperature has been increasing at a rate of +0.142 °C each year since 2013. This is particularly alarming when compared to the +0.028 °C yearly increase reported between 1991 and 2012.
The summer of 2022 was also confirmed to be the hottest season in recorded European history, with a mean temperature of 20.30 °C, which was higher than the previous hottest summer of 2003 at 20.20 °C. Regression analyses suggest that 35.3 additional individuals die/million for every 1 °C temperature increase.
Conclusions
The current study utilized epidemiological models to investigate and quantify heat wave-related mortality in the summer of 2022 in Europe. These models indicate that age has a vital role in resilience to heat stress, with older individuals at an increased risk than those up to 64 years of age.
Previous studies have shown that the risk of heat wave-related death has reduced since 2003 in many European countries. The study findings disprove this observation and highlight how, while interventions may have helped in the short-term, mortality across the continent in 2022 matched and almost exceeded the record-breaking mortality of 2003.
Despite the fact that many European countries activated heat prevention plans during the summer of 2022, the estimation of over 60,000 heat-related deaths suggests that prevention plans were only partially effective.”
The study findings call on European governments to design and implement novel solutions to prevent and adapt to heat stress. Unless policies and interventions can improve human adaptation to heat, 68,116 individuals will die every summer by 2030, 94,363 individuals by 2040, and 120,610 individuals by 2050.
Researchers gain new understanding of how immune cells respond to heat during fever