Study Redefines Dangerous Heat Thresholds for Seniors and Adults

Researchers at the University of Sydney have identified new temperature‑humidity limits at which the human body begins to suffer serious stress. The study finds that healthy young adults start experiencing dangerous thermal strain between 26 °C and 34 °C, while seniors are at risk from as low as 21 °C, especially when humidity impedes sweat evaporation. Each degree above 24 °C raises the risk of cardiac events by about 3.5 %, and prolonged exposure can lead to dehydration, kidney failure and arrhythmia.

French health broadcasters have echoed the findings, warning that extreme heat increases dehydration risk and that alcohol consumption should be avoided because it worsens fluid loss and can overload emergency services. They advise staying well‑hydrated, using cool‑mist devices rather than fans in very hot, dry air, and keeping indoor temperatures below 20 °C at night to aid recovery for vulnerable populations.