Is an Adjustment in the Recommended Indoor Temperature Upper Limit of 26°C Required During Higher Levels of Humidity?

What this Trial Is About

Researchers are studying how indoor humidity affects physical stress, especially in older adults aged 65 to 85 years, during heat exposure. The study focuses on whether the current recommended indoor temperature limit of 26°C needs adjustment when humidity levels change, as higher humidity may worsen heat stress by reducing sweat evaporation. This is important because climate change is increasing both temperature and humidity, which could increase health risks for vulnerable people. Participants will experience four different indoor conditions on separate occasions: 26°C at 45% humidity, 26°C at 15% humidity, 26°C at 85% humidity, and 31°C at 45% humidity. Each session lasts 10 hours, simulating a daylong heat exposure. By comparing similar perceived temperatures (humidex), investigators aim to understand how both temperature and humidity affect the body’s response to heat. During the study, researchers will measure core body temperature, heart rate, blood pressure, balance, cognitive function, mood, thirst, and fluid loss before and after exposure. They will use various scales and tests to assess physical and mental effects of heat and humidity. The study uses a randomized design with single masking and will monitor participants throughout the 10-hour exposure periods to gather detailed information on heat strain and comfort.

Influence of Indoor Humidity on Physiological Strain in Older Adults During a Simulated Heat Wave