New research from Griffith University indicates that maintaining a bedroom at 24°C (75°F) during the night can lower stress responses and improve heart efficiency for people aged 65 and older. The study highlights how heat disrupts sleep recovery, particularly amid rising nighttime temperatures due to climate change. Findings were gathered using wearable trackers and room sensors during an Australian summer.
Researchers at Griffith University have identified a potential benefit in keeping bedrooms cooler at night for older adults. Led by Dr. Fergus O'Connor from the School of Allied Health, Sport and Social Work, the observational study examined the impact of nighttime temperatures on heart rate variability and stress levels in individuals aged 65 and over.
Participants wore fitness activity trackers on their non-dominant wrist to monitor heart-related data during sleep. Temperature sensors in their bedrooms recorded conditions continuously over the Australian summer. The results showed that a bedroom temperature of 24°C reduced the likelihood of heightened stress responses, allowing the heart to function more efficiently.
Dr. O'Connor explained the physiological effects: "When the human body is exposed to heat, its normal physiological response is to increase the heart rate. The heart is working harder to try and circulate blood to the skin surface for cooling. However, when the heart works harder and for longer, it creates stress and limits our capacity to recover from the previous day's heat exposure."
The study provides the first real-world evidence linking higher bedroom temperatures directly to elevated heart rates and stress during sleep. Dr. O'Connor noted the broader implications: "For individuals aged 65 years and over, maintaining overnight bedroom temperatures at 24°C reduced the likelihood of experiencing heightened stress responses during sleep."
With climate change increasing hot nights, these findings are timely. "Climate change is increasing the frequency of hot nights, which may independently contribute to cardiovascular morbidity and mortality by impairing sleep and autonomic recovery," Dr. O'Connor said. Currently, guidelines exist for daytime indoor temperatures, capping them at 26°C, but none for nighttime conditions.
The research, titled 'Effect of nighttime bedroom temperature on heart rate variability in older adults: an observational study,' was published in BMC Medicine in 2025.