Chronic Heat Exposure Poses Growing Health Threat Amid Climate Change

In recent weeks, extreme heatwaves have grippedd the United States, China, and Europe. Yet scientists warn that persistent high temperatures—even those not meeting official heatwave criteria—can also pose serious health risks. In many regions, prolonged periods of moderately elevated temperatures may lead to chronic conditions such as kidney dysfunction, sleep apnea, and depression. Researchers at the University of Miami emphasize that the cumulative health impacts of long-term heat exposure remain significantly understudied.

Experts note that climate change is increasing the number of high-temperature days globally, highlighting the urgent need for more comprehensive research. While heatwaves are typically defined as brief periods when temperatures exceed a certain threshold, baseline temperatures in tropical and subtropical regions may already be dangerously high. In Miami, for instance, the heat index—a measure combining temperature and humidity—exceeds 90°F (32°C) on about half of all days annually.

Compelling evidence comes from studies on agricultural workers in Central America, linking long-term heat exposure to chronic kidney disease. Access to hydration, shade, and rest can slow kidney decline, but research on other health risks remains limited. A University of Washington analysis of seasonal high-temperature regions found no definitive evidence that these areas experience higher mortality—yet.

Nonetheless, prolonged heat can exacerbate existing health issues. Research from Arizona State University shows that high temperatures alter blood distribution and can worsen conditions related to inflammation and circulation. Some medications, such as diuretics or certain antipsychotics, may become less effective—or even harmful—during heat exposure by impairing sweating or reducing fluid levels.

Urban heat retention at night also disrupts sleep. Studies reveal that hot nights increase the risk of sleep apnea, with global warming linked to an annual average loss of 44 hours of sleep per person. This disruption, with little seasonal adaptation, may contribute to cardiovascular, metabolic, and broader health decline. Cognitive performance is also at risk—research among U.S. high school students shows that classroom learning efficiency drops significantly on hotter days.

Vulnerable populations are most affected, often lacking access to adequate cooling resources. The University of Miami researchers note that these communities are frequently overlooked in studies, despite bearing the brunt of long-term heat exposure. As the planet continues to warm, addressing the impacts of chronic heat will become increasingly critical.