Estimating the temporal adaptation and spatial vulnerabilities of the heatwave mortality risk in Greece

IntroductionGlobal temperatures are rising due to anthropogenic greenhouse gas emissions. Record-breaking temperatures observed in Europe during the summer of 2022 were associated with more than 60,000 heat-related deaths, with countries near the Mediterranean Sea, particularly Greece, being most affected. This study explores the death toll of prolonged heat periods in Greece, its spatial disparities, and how these patterns have changed over time.MethodsWe retrieved individual-level data on cause-specific mortality in Greece during 2000-2019 from the Hellenic Statistical Authority. The data included information on age, sex, cause of death, region of residence (Nomenclature of Units for Territorial Statistics, level 3; NUTS3), and date of death. Daily maximum temperatures during 2000–2019 at 0.25° x 0.25° resolution were retrieved from ERA-5 reanalysis data. We considered six heatwave definitions, combining two durations (>2 and >3 days) and three temperature thresholds (90th, 95th, and 99th percentiles). A Bayesian hierarchical Poisson model was developed, accounting for spatiotemporal variation in heatwave effects using Gaussian priors. We also controlled for national holidays and population-weighted relative humidity.ResultsWe observed 177,112 cardiovascular deaths and 39,646 respiratory deaths in individuals aged 65 and older in Greece during 2000–2019. A strong association was found between heatwaves and cardiovascular and respiratory mortality under all definitions. Evidence of spatial variation in heatwave effects was weak, as was evidence of temporal adaptation. However, for the most extreme heatwave definition, we observed an increasing trend in the effect of heat over the study period. Over 20 years, 6,926 (95% CI: 6,260–7,587) cardiorespiratory deaths were attributed to heatwaves, equating to approximately 350 deaths per year.ConclusionHeatwaves impose a significant mortality toll in Greece. While the effect of heatwaves on mortality has not changed over time in most heatwave definitions, the increasing trend of the effect of extreme heatwaves calls for immediate action to mitigate future risks.Funding:EUREST-RISE