Study links warmer bedroom temperatures to higher heart stress during sleep

A growing body of research suggests your nighttime thermostat setting may affect more than just comfort—it could also play a role in heart health.

A recent study published in BMC Medicine found that warmer bedroom temperatures during sleep were linked to higher heart rates and reduced heart rate variability (HRV), a key indicator of how well the body is recovering and managing stress.

Hotter Nights, Heavier Strain on the Heart

Researchers observed that participants sleeping in warmer environments showed signs that their autonomic nervous system was under greater strain rather than resting and recovering.

The study found that when bedroom temperatures rose above 75°F (24°C), the risk of reduced HRV increased by around 40%. At temperatures above 82°F (28°C), the likelihood of lower HRV was nearly three times higher.

Experts say these changes may signal that the heart is working harder overnight instead of resting.

“Cooler temperatures at night could help to reduce stress on the heart while you sleep,” said Joyce M. Oen-Hsiao.

Why Heat Affects Sleep and Heart Function

Health specialists explain that the body naturally lowers its core temperature during sleep to support deeper rest. However, warmer rooms can interfere with this process.

When the environment is too hot, the body may increase blood flow to the skin to release heat, which can raise heart rate. Excess sweating can also lead to mild dehydration, further affecting cardiovascular function.

“Warmer temperatures can place extra stress on the body during sleep,” said Robert L. Gottlieb.

Sleep specialist Alex Dimitriu added that disrupted temperature regulation may also reduce time spent in REM sleep, the stage associated with memory, mood, and cognitive recovery.

Study Findings and Limitations

The study monitored 47 older adults in Queensland, Australia, who wore heart-tracking devices while sleeping. Bedroom temperatures were recorded throughout the night, ranging from below 75°F to as high as 90°F (32°C).

While the data—spanning more than 14,000 hours of sleep—showed a strong association between heat and heart stress markers, researchers noted several limitations. The study was small and did not account for whether participants used air conditioning or fans. It was also observational, meaning it could not prove direct cause and effect.

What Experts Recommend

There is no universal “perfect” sleep temperature, but prior research typically places the ideal range between 68°F and 77°F (20°C to 25°C).

The World Health Organization advises that indoor temperatures should generally not exceed 79°F (26°C), although it does not provide specific nighttime guidance.

Experts stress that personal comfort still matters. However, frequent night sweating or disrupted sleep may indicate that your bedroom is too warm.

During heatwaves, cooling strategies such as air conditioning, fans, or improved ventilation may help support both sleep quality and cardiovascular health.