How to reduce cardiovascular crisis risk by adjusting bedroom temperature

Author: Gao Jie In the context of global warming, extreme high-temperature weather is becoming increasingly frequent. Nights, which should be a time for the body to relax and regain energy, are being quietly threatened by the rising temperatures in bedrooms, posing a serious risk to the cardiovascular health of the elderly.

A recent study published in BMC Medicine revealed the impact of nighttime bedroom temperature on heart rate and heart rate variability in older adults, providing key evidence for the establishment of indoor temperature standards during the night.

Source of the image: Research screenshot

"Keeping the bedroom temperature at 24°C for individuals aged 65 and older can reduce the likelihood of heightened stress responses during sleep," said Dr. Fergus O'Connor from the Griffith University School of Health, Sport and Human Performance.

The research team stated that the World Health Organization has only established a guideline for the maximum indoor temperature during the day (26°C), while the nighttime bedroom temperature, which is closely related to sleep quality and bodily recovery, has long been overlooked. Therefore, they focused on how elevated nighttime bedroom temperatures impact the heart rate and stress levels of the elderly, aiming to provide scientific support for ensuring the nighttime health of older adults.

How does high temperature quietly damage the cardiovascular system of the elderly? Dr. O'Connor provides an in-depth explanation of the significant burden that high temperatures place on the cardiovascular system of older adults, revealing the core mechanisms by which high nighttime temperatures affect their health. He notes that the bodily functions of the elderly gradually decline, leading to a much lower capacity for temperature regulation and cardiovascular reserve compared to younger individuals. During nighttime sleep, the body's metabolism slows down, and the autonomic nervous system enters a state of regulation and repair. In this state, the effects of high temperatures are more subtle and enduring.

When the body is exposed to high-temperature environments, the usual physiological response is an increased heart rate as the heart works harder to pump blood to the skin's surface, facilitating heat dissipation through sweat evaporation. This process may seem routine, but it conceals potential dangers. For older adults, prolonged periods of high cardiac workload can lead to heart fatigue and sustained increases in heart rate. Additionally, it can intensify physiological stress responses, limiting the body's ability to recover from the previous day's heat exposure, which can ultimately lead to a series of cardiovascular issues over time.

The study on the core relationship between temperature and health will be conducted from December 2024 to March 2025 during the Australian summer, involving comprehensive monitoring of 47 community-dwelling older adults aged 65 and above in Southeast Queensland.

To obtain the most authentic and accurate data, the research team implemented a dual monitoring method: Participants wore fitness activity trackers on their non-dominant wrist, continuously recording heart rate and heart rate variability data during sleep; simultaneously, a temperature sensor installed in the bedroom continuously monitored the nighttime environmental temperature at 10-minute intervals throughout the study period. Ultimately, the research successfully collected 14,179 valid nighttime monitoring hours, with a median bedroom nighttime temperature of 25.9℃ during the monitoring period.

The study categorizes nighttime bedroom temperatures into four gradients: <24°C, 24-26°C, 26-28°C, and 28-32°C, with <24°C serving as the reference group.

Analysis reveals that higher temperatures correlate with an increased risk of cardiovascular health issues in the elderly. Specifically, at temperatures between 24-26°C, the likelihood of significant clinical reductions in lnRMSSD (a key indicator of heart rate variability) for older adults increases by 1.4 times; this rises to 2.0 times at 26-28°C, and escalates to 2.9 times at 28-32°C. Furthermore, elevated temperatures are also associated with decreases in lnHF and lnLF (high-frequency and low-frequency heart rate variability), an increase in ln(LF:HF) (the low-high frequency ratio), and a rise in heart rate.

These data clearly indicate that an increase in bedroom temperature at night directly affects heart rate and stress responses during sleep, causing harm to the autonomic nervous system and cardiovascular system of the elderly. Notably, this effect does not differ regardless of whether participants are taking heat sensitivity-related medications, suggesting that the risk is widespread.

As climate change intensifies, the frequency of hot nights is on the rise. Dr. O'Connor notes that this could independently increase the incidence and mortality rate of cardiovascular diseases.

This study not only provides the first direct evidence of the association between nighttime temperature and the cardiovascular physiological status of the elderly in real-life scenarios, clearly identifying the critical protective threshold of 24°C, thus filling a research gap, but it also points to a direction for health protection in the summer for seniors—keeping the nighttime bedroom temperature below 24°C is key to maintaining stable autonomic nervous function and reducing cardiovascular physiological stress.

In addition, the research provides data support for the formulation of public health policies. In the future, it is necessary to incorporate nighttime indoor temperature thresholds into the framework for heat health protection. By monitoring indoor temperatures and implementing early warning systems for high-risk populations, we can reduce the adverse effects of high nighttime temperatures on the health of the elderly.