Twenty-Seven Ways a Heat Wave Can Kill You: Deadly Heat in the Era of Climate Change.

Heat waves, sporadic events of extreme heat, pose a threat to human life. Deaths in excess of 70 000 people during the 2003 European heat wave, 10 000 people during the 2010 Russian heat wave, and high death tolls from numerous other heat waves1 are staggering demonstrations that extreme climatic conditions are already exceeding human thermoregulatory capacity. The area of the planet experiencing heat wave conditions similar to those that have killed people is expanding and is currently inhabited by ≈30% of the world’s human population.1 Because the planet will warm another 1°C by 2100 if we curtail greenhouse gases or 3.7°C if we do not, our choices for deadly heat are now between more of it or a lot more of it.1 Here we carried out a systematic synthesis of deadly heat physiological pathways to make the point that the human body is sensitive to heat and that heat waves can harm anyone (even the young and healthy2,3) in ways that extend beyond cardiovascular diseases. We suggest that only the rapid reduction of greenhouse gases paired with large economic investment in adaptation will help us escape the health risks of heat waves. Ambient conditions that prevent body heat dissipation (eg, too hot, too humid, or both) trigger dangerous physiological responses or pathways that have been a topic of considerable medical interest for “military personnel, athletes, and occupations exposed to extreme heat, such as mining.”4 To systematically synthetize these deadly pathways, we searched online databases (ie, PubMed and Google Scholar) using the key words pathophysiology and heat illness , heat stroke , or heat stress . We categorized pathways in a table listing physiological mechanisms by columns and vital organs impacted by rows. We performed secondary searches combining as key words the mechanism (column name) …