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Cooler bedroom temperatures help the heart recover during sleep:

Maintaining a bedroom temperature of 24°C [75°F] at night while sleeping reduces stress responses in older adults, according to new Griffith University research.

Dr Fergus O'Connor from Griffith's School of Allied Health, Sport and Social Work assessed the effect of increasing nighttime bedroom temperatures on heart rate and stress responses in older adults.

"For individuals aged 65 years and over, maintaining overnight bedroom temperatures at 24°C reduced the likelihood of experiencing heightened stress responses during sleep," Dr O'Connor said.

"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."

Study participants wore fitness activity trackers on their non-dominant wrist, and the bedroom temperature was monitored via installed temperature sensors throughout the Australian summer-long data collection period.

The data from the study provided the first real-world evidence of the effect of increasing bedroom temperature had on heart rate and stress responses.

"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.

"While there are guidelines for maximum daytime indoor temperature, 26°C, there are no equivalent recommendations for nighttime conditions."

Journal Reference: O'Connor, F.K., Bach, A.J.E., Forbes, C. et al. Effect of nighttime bedroom temperature on heart rate variability in older adults: an observational study. BMC Med 23, 703 (2025). https://doi.org/10.1186/s12916-025-04513-0

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