We all want to sleep well.

And we do all kinds of things, some of them crazier than others, to get a good night’s sleep.

But what you do to the air in your bedroom could be worse for your sleep than a number of other seemingly “harmful” activities.

So, if you’re somewhat older (that could be even 65…or even 50), you’ll want to do this with the thermostat in your bedroom.

What You Should Set Your Thermostat At in Your Bedroom

Keep your bedroom under 75 degrees at night.

That is the takeaway from new research from Griffith University, where investigators tracked bedroom temperatures and heart activity in adults aged 65 and older during the Australian summer.

The findings suggest that once nighttime bedroom temperatures rise above about 75.2°F, the cardiovascular system may start working harder even while a person is asleep.

For older adults, that matters.

The body generally becomes less efficient at handling heat with age, and hot nights can make it more difficult to recover from daytime heat exposure.

Naturally, when the body gets hot, it tries to cool itself by moving more blood toward the skin.

That requires the heart to beat faster.

During the day, that response may not seem unusual. During sleep, however, the body should shift toward rest and recovery. If the heart continues working harder through the night, some of that recovery may be lost.

Researchers looked at heart rate variability, or HRV, to gauge how much physiological strain participants were experiencing.

HRV measures small differences in the amount of time between heartbeats. In general, healthier overnight recovery is associated with greater activity from the parasympathetic nervous system, often called the body’s “rest-and-digest” system.

Lower HRV can suggest the body is under more stress.

What Researchers Found

The study followed 47 adults aged 65 and older who were living independently in southeast Queensland, Australia.

Participants wore Fitbit Inspire 3 trackers, and sensors continuously measured bedroom temperatures. Researchers collected data during one summer, from December 2024 through March 2025.

They analyzed more than 14,000 hours of nighttime data.

The typical bedroom temperature was about 78.6°F, meaning many participants were regularly sleeping in rooms warmer than the level associated with the lowest physiological strain.

The pattern was fairly clear.

Compared with nights when bedrooms stayed below 75.2°F, the odds of a meaningful reduction in one important HRV measure increased as rooms became hotter.

At 75.2°F to 78.8°F, the odds were about 40% higher. Between 78.8°F and 82.4°F, they were roughly twice as high. At temperatures between 82.4°F and 89.6°F, they were nearly three times as high.

Hotter rooms were also associated with higher heart rates and other changes suggesting greater activation of the body’s “fight-or-flight” response.

In other words, the body appeared to be working harder when it should have been resting.

What This Means at Home

The study does not prove that a bedroom above 75°F directly causes heart disease, and it was relatively small. It also involved older adults living in one region of Australia, so the findings may not apply equally to everyone.

Still, the research raises a practical issue that is likely to become more important as nighttime temperatures rise.

Keeping a bedroom below about 75°F may be worth considering, especially for older adults and people who already have difficulty tolerating heat.

Air conditioning is the obvious solution, but it is not equally affordable or available to everyone. Fans, lighter bedding, closing blinds during the hottest part of the day, improving airflow, and moving sleeping areas to cooler parts of the home may also help.

People taking medications that affect hydration, blood pressure, or temperature regulation may have additional reasons to be cautious during periods of extreme heat and should discuss concerns with their healthcare provider.

The bigger point is simple. Heat exposure does not stop mattering when someone goes to bed.

A hot bedroom can keep the cardiovascular system working when the body would normally be trying to recover. For older adults in particular, a slightly cooler room may make nighttime rest easier on the body.