Your bedroom temperature could be putting your heart in serious danger, study warns

Heat places extra demands on the cardiovascular system, according to lead study author Dr. Fergus O'Connor from Griffith University in Queensland, Australia.

When the human body is exposed to heat, its reaction is to work harder to try and circulate blood to the skin surface for cooling, he noted.

"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," O'Connor stated in a press release.

The team followed 47 adults living in southeast Queensland averaging 72 years of age.

While many sleep observations are conducted in special clinics, this was a "free-living" study, meaning the participants carried on with their normal activities and sleep schedules.

Sensors were then placed directly in participants' bedrooms to record the temperatures, monitoring over 14,000 nighttime hours of sleep in total.

The temperature at which the heart began to show signs of disruption was a little more than 75 degrees Fahrenheit.

Between 79 and 82 degrees Fahrenheit, the odds doubled. Above 82, the risk was nearly triple compared to cooler rooms.

"For individuals aged 65 years and over, maintaining overnight bedroom temperatures at 24 C (75.2 F) reduced the likelihood of experiencing heightened stress responses during sleep," O'Connor said.

While the study shows a strong link between heat and heart stress, its observational design means that it doesn't definitively prove heat is the only cause, the researchers acknowledged. 

As the study only focused on older adults in Australia, it may not apply to other populations.

O'Connor emphasized a gap in temperature guidance - while there are guidelines for maximum daytime indoor temperature, there are no equivalent recommendations for nighttime conditions.

The study was published in the journal BMC Medicine.