With summer fast approaching along with the inevitable heat and humidity, new Griffith University research is proving to be a timely reminder about the dangers of hot homes and the serious strain it can place on older Australians when the indoor temperature exceeds 26°C.
A team of researchers monitored the physiological effects of indoor overheating on older adults under real-world living conditions across an Australian summer in South East Queensland.
They followed 47 community-dwelling adults aged 65 years and older and monitored their heart rate and physical activity, plus temperature and humidity data between December 2024 and March 2025, cataloguing more than 64,000 hours of data.
Indoor temperatures above 26°C increased cardiovascular stress in older adults with their heart rate increasing almost twice as rapidly compared with temperatures below 26°C.
The research provided real-world evidence that hot homes were a health issue, not just a comfort issue.
Lead author Dr Fergus O'Connor from Griffith's School of Allied Health, Sport and Social Work said older adults spend most of their time indoors, yet most heat-health advice focused on outdoor temperatures.
"Indoor heat exposure can place substantial strain on the heart and can remain this way for up to several hours after exposure suggesting cardiovascular strain accumulates and persists even after the mercury begins to fall," Dr O'Connor said.
The results reinforced the World Health Organisation's temperature recommendations and highlighted the need for improved housing design, affordable cooling solutions, targeted heat-health messaging, and support for heat-vulnerable populations.
Dr Aaron Bach said for every 1°C increase in indoor temperature, heart rate increased by approximately 0.6 beats per minute.
"When the mercury reached or exceeded 26°C, heart rate increased by 1.3 beats per minute per degree Celsius, nearly double the rate observed below the threshold," Dr Bach said.
"Interestingly, it was the indoor temperature rather than humidity which was the primary factor associated with increased cardiovascular strain."
The paper 'Indoor temperatures above 26°C impose disproportionate cardiovascular strain on older adults' has been published in Temperature.
