A new study from Griffith University has found that indoor temperatures above 26°C increased cardiovascular stress among adults aged 65 and older, doubling heart rates in some instances.
The research, published on Thursday, tracked nearly 50 community-dwelling adults aged 65 and older between December 2024 and March 2025. Participants wore wearable fitness trackers while temperature and humidity sensors were placed in their homes.
Lead author Dr Fergus O'Connor from Griffith's School of Allied Health, Sport and Social Work said the findings align with the World Health Organisation's recommended indoor occupancy threshold of 26 degrees. "Physiologically, it makes sense. As temperatures get higher, the cardiovascular [blood] vessels and system has to work harder and harder," he said.
The study found heart rate increased by about 0.6 beats per minute for every one-degree increase in indoor temperature. Co-author Dr Aaron Bach said that when temperatures reached or exceeded 26°C, heart rate increased by 1.3 beats per minute per degree, “nearly double the rate observed below the threshold.”
O’Connor said that while marginal increases in heart rate may seem inconsequential, stress is easily elevated in older adults. “It starts adding into the thousands of additional beats in a day that otherwise wouldn't have been made,” he said. “The stress keeps compounding.”
Health worker Michelle Byard brings her 85-year-old mother from the Sunshine Coast to her own air-conditioned home in Brisbane during hot weather. Her mother's rental lacks sufficient cooling. “The landlords haven't put in air-conditioning for her, so we've had to get a portable device,” Byard said. “But in the middle of summer … it's not that effective, and still does cost extra money to run.” Byard, a member of the Queensland Community Alliance, said older people worry through summer. “For years I've been aware that extreme heat, the summers here in Queensland in particular, are causing stress for people,” she said. “It's not only discomfort; it's around their health as well.”
Sweltering Cities founder Emma Bacon said the findings should prompt action. "Unfortunately, too many people are in low-energy efficiency homes that get hot and are expensive to cool," Bacon said. "The percentage of older Queenslanders living in rentals is increasing, which means they're more likely to be living in a home that puts their heart health at risk. A clear way to make sure older Queenslanders aren't being put at risk of heart health issues is to bring in minimum standards for rentals – all of us need healthy housing."
Analysis
Why This Matters
- The study provides direct physiological evidence linking indoor heat to cardiac strain in seniors, a group already vulnerable to heat-related illness and death.
- As Australia's rental market tightens and summers intensify, older renters may face worsening health risks without minimum housing standards for cooling.
- The findings could inform policy debates on rental property regulations, energy efficiency subsidies, and heat health warnings.
Background
The research comes as south-east Queensland experiences early-season temperatures in the mid-30s. Older adults are particularly susceptible to heat stress due to reduced cardiovascular function and, often, limited access to air conditioning. The World Health Organisation recommends keeping indoor temperatures at or below 26°C for vulnerable populations. Australia's rental laws currently lack binding minimum temperature standards in most states.
Key Perspectives
Dr Fergus O'Connor (Griffith University): said the physiological link is clear: as indoor temperatures rise above 26°C, the cardiovascular system works harder, leading to an elevated heart rate that compounds throughout the day.
Emma Bacon (Sweltering Cities): said the findings should be a wake-up call, calling for minimum rental standards to ensure all homes are healthy and safe during heat events.
What to Watch
- Whether Queensland or other state governments introduce minimum energy-efficiency or cooling standards for rental properties.
- Expansion of the study to other regions or populations to gauge broader heat-health impacts.
- Upcoming summer heatwave events that could test the resilience of older residents in poorly insulated homes.
Checked
12 claims in this story checked against 1 source: 11 supported.
Show each claim
- Partly supportedIndoor heat can double heart rates in some older Queenslanders.WA Today - Latest News: “The results showed indoor temperatures above 26 degrees increased the age group’s cardiovascular stress, doubling their heart rate in some instances, compared to temperatures below 26 degrees.”
- SupportedThe research found cardiovascular stress rises above 26°C.WA Today - Latest News: “The results showed indoor temperatures above 26 degrees increased the age group’s cardiovascular stress”
- SupportedSweltering Cities founder Emma Bacon warned that older renters’ heart health is at risk.WA Today - Latest News: “The percentage of older Queenslanders living in rentals is increasing, which means they’re more likely to be living in a home that puts their heart health at risk.”
- SupportedThe study tracked nearly 50 community-dwelling adults aged 65 and older between December 2024 and March 2025.WA Today - Latest News: “The research, led by Griffith University and published on Thursday, collected data from nearly 50 community-dwelling adults in south-east Queensland aged 65 years and older. Between December 2024 and March 2025, the participants were given wearable fitness trackers”
- SupportedLead author Fergus O’Connor said the findings align with the WHO’s recommended indoor occupancy threshold of 26 degrees.WA Today - Latest News: “Lead author Dr Fergus O’Connor from Griffith’s School of Allied Health, Sport and Social Work said the findings reflect the World Health Organisation’s recommended indoor occupancy threshold of 26 degrees.”
- SupportedO’Connor said: “Physiologically, it makes sense. As temperatures get higher, the cardiovascular [blood] vessels and system has to work harder and harder.”WA Today - Latest News: ““Physiologically, it makes sense. As temperatures get higher, the cardiovascular [blood] vessels and system has to work harder and harder,” he said.”
- SupportedHeart rate increased by about 0.6 beats per minute for each one-degree increase in indoor temperature.WA Today - Latest News: “For every one-degree increase in indoor temperature, heart rate increased by approximately 0.6 beats per minute.”
- SupportedCo-author Aaron Bach said that at or above 26°C, heart rate increased by 1.3 beats per minute per degree, nearly double the rate below the threshold.WA Today - Latest News: “Co-author Dr Aaron Bach said when the mercury reached or exceeded 26 degrees, heart rate increased by 1.3 beats per minute per degree Celsius. “[That’s] nearly double the rate observed below the threshold,” Bach said.”
- SupportedO’Connor said the extra beats add up to thousands in a day and that the stress keeps compounding.WA Today - Latest News: ““It starts adding into the thousands of additional beats in a day that otherwise wouldn’t have been made,” he said. “The stress keeps compounding.””
- SupportedByard said her mother’s landlords had not installed air-conditioning, so they got a portable device, which was ineffective in mid-summer and cost extra to run.WA Today - Latest News: ““The landlords haven’t put in air-conditioning for her, so we’ve had to get a portable device,” Byard said. “But in the middle of summer … it’s not that effective, and still does cost extra money to run.””
- SupportedByard said extreme heat, particularly Queensland summers, causes stress for people and affects their health, not only their comfort.WA Today - Latest News: ““For years I’ve been aware that extreme heat, the summers here in Queensland in particular, are causing stress for people,” she said. “It’s not only discomfort; it’s around their health as well.””
- SupportedBacon said the percentage of older Queenslanders living in rentals is increasing, putting them more likely to live in homes that risk their heart health.WA Today - Latest News: ““The percentage of older Queenslanders living in rentals is increasing, which means they’re more likely to be living in a home that puts their heart health at risk.”
