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Heat waves stand out among the increasingly frequent extreme weather events that result from climate change. Their impact on health, ranging from heat strokes to worsened psychiatric conditions, is well known, but until now, there have been only local-level data. Now, thanks to a study published in May by PLoS Medicine, we have a high-resolution global map of heat wave mortality between 1990 and 2019. The analysis of geographical variations shows that Southern Europe, and particularly Italy, is among the most affected areas worldwide.

An international collaboration led by Monash University in Melbourne, Australia, collected data from 750 locations on heat wave mortality. Heat waves were defined as temperatures above the 95th percentile of the annual average sustained for more than 2 days. Researchers calculated the impact on the entire planet to obtain a global estimate of mortality.

The Overall Situation

Researchers estimate that on average, between 1990 and 2019, heat waves have caused more than 153,000 deaths per year. This toll is equivalent to 236 deaths per 10 million people, or almost 1% of total deaths during the warm seasons. There is significant heterogeneity in mortality among the various locations on the planet. The relative mortality of heat waves seems to be highest in Southern Europe. In that region, heat waves cause 2.32% of deaths during the warm seasons, or 668 excess deaths per 10 million people. Italy, where 2.47% of deaths are attributable to heat waves, is one of the most affected countries in the world, along with Malta and Greece.

On a global level, the number of deaths due to heat waves has decreased from 261 deaths per 10 million people in the 1990s to 227 in the 2010s. However, the percentage of total deaths caused by heat waves remains substantially stable around 1%. In other words, while mortality from all causes has decreased (especially in Africa), the impact of heat waves has not decreased proportionally. In Europe and much of Asia, this impact is increasing, both in terms of the percentage of deaths and the number of deaths per inhabitant, especially in Southern and Eastern Europe and Western Asia. In Italy, the estimated percentage of deaths caused by heat waves has remained substantially unchanged (from 2.47% to 2.48%).

The study has some limitations, such as the scarcity of data in regions like the Arabian Peninsula and Southern Asia. Nevertheless, it allows us to understand how the impact of heat waves varies in space and time. The study therefore provides a starting point on which various regions of the world, including Italy, can modulate their actions.

The Italian Situation

"Our results, which show that heat waves are associated with significant mortality that has varied in space and time worldwide over the past 30 years, suggest that planned adaptation is needed, based on local conditions and risk management at all government levels," said Yuming Guo, MD, PhD, professor of global health and biostatistics at Monash University and one of the main authors of the study. In Italy, heat waves have long been monitored by the Ministry of Health. The national prevention system has just restarted. Although there was a slight decrease in mortality in the summer of 2023, they remain a public health problem, especially in southern regions. In addition to the usual recommendations for the public, in July 2023, the Civil Protection Department recommended the implementation of various measures to address heat waves. The recommendations include the application of a separate "heat code" in emergency rooms to manage admissions (which totaled more than 6600 per day in the second half of July 2023), the activation of territorial clinics for 12 hours per day on 7 days per week for access related to heat effects, and the strengthening of home care. It's best to be prepared because the European climate monitoring system Copernicus forecasts an extremely hot summer.

This story was translated from Univadis Italy, which is part of the Medscape professional network, using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.