Maintaining a bedroom temperature of around 24°C overnight can help reduce stress responses in older adults during sleep, according to new research from Griffith University.
The study, led by Dr Fergus O’Connor from Griffith’s School of Allied Health, Sport and Social Work, examined how higher night-time bedroom temperatures affect heart rate and physiological stress in people aged 65 and over. The findings suggest that keeping bedrooms at 24°C while sleeping lowers the likelihood of heightened stress responses during the night.
Dr O’Connor explained that exposure to heat triggers a natural physiological reaction in the body, causing the heart rate to rise. As temperatures increase, the heart works harder to circulate blood towards the skin in an effort to dissipate heat and cool the body. While this response is regular, prolonged periods of elevated heart activity place additional strain on the cardiovascular system and reduce the body’s ability to recover from heat exposure accumulated during the day.
When the heart continues to work harder for extended periods overnight, this added stress can interfere with the restorative functions of sleep. Over time, such strain may have implications for overall cardiovascular health, particularly in older adults who are more vulnerable to heat-related stress.
To capture real-world data, participants in the study wore fitness activity trackers on their non-dominant wrist to continuously monitor heart rate and stress indicators. Bedroom temperatures were recorded using installed temperature sensors, allowing researchers to closely track environmental conditions throughout the Australian summer-long data collection period. This approach enabled the team to assess how naturally occurring temperature variations influenced physiological responses during sleep, rather than relying on laboratory-based simulations.
The findings provide some of the first real-world evidence demonstrating how increased bedroom temperatures can affect heart rate and stress responses overnight. According to Dr O’Connor, the results highlight an often-overlooked aspect of thermal health: night-time indoor conditions.
The research also has broader implications in the context of climate change. Rising global temperatures are increasing the frequency of hot nights, which may independently contribute to higher rates of cardiovascular illness and mortality. This occurs not only through direct heat exposure but also by disrupting sleep and impairing the body’s autonomic recovery processes that generally take place overnight.
Despite the known risks associated with excessive indoor heat during the day, clear guidance for nighttime temperatures is lacking. While there are established recommendations for maximum indoor daytime temperatures, set at 26°C, no equivalent standards exist for overnight sleeping environments. The researchers suggest that developing evidence-based guidelines for nighttime bedroom temperatures could play an essential role in protecting cardiovascular health as climates continue to warm.
More information: Fergus K. O’Connor et al, Effect of nighttime bedroom temperature on heart rate variability in older adults: an observational study, BMC Medicine. DOI: 10.1186/s12916-025-04513-0
Journal information: BMC Medicine Provided by Griffith University
