The Physiology behind the Epidemiology of Heat-Related Health Impacts

A direct consequence of climate change is the intensification of hot weather and extreme heat events that are epidemiologically associated with a greater risk of heat-related illnesses and other adverse health outcomes, often resulting in subsequent hospital admissions and mortality. The health risks associated with hot weather directly arise from the body's physiological responses (i.e., heat strain) to heat exposure. The magnitude of heat strain experienced and the extent of heat strain required to cause an adverse health outcome can be modulated by personal characteristics and the adoption of protective behaviors. This review presents the pathophysiological mechanisms responsible for the epidemiological association between heat exposure and a greater risk of heat illnesses (e.g., heat exhaustion, heatstroke), adverse cardiovascular events, and acute kidney injury or failure. These mechanisms are framed within the larger context that defines heat-related health risks, and we provide examples and perspectives of how physiologists are uniquely positioned to contribute to risk reduction and adaptation efforts to protect humans against the adverse health impacts of heat, while maintaining optimum well-being and performance.