If you sleep in a slightly cooler environment than you might be used to, your sleep will be deeper and your recovery will be faster. This was discovered by American scientists who had women sleep on a gel mattress that dissipates heat more effectively. A slightly thinner blanket might have the same effect, we suspect.

Study
Neurologists at Northwestern University had 24 healthy postmenopausal women, aged 40–75, sleep overnight on two separate occasions. On one occasion, the women slept on a more or less regular mattress, and on the other, on a gel mattress.

The gel mattress contained a layer of gel that dissipates and absorbs body heat more effectively than the filling of regular mattresses. This makes a gel mattress feel cooler than a regular mattress. The manufacturer of such mattresses, the Italian company Technogel, funded the study.

The researchers monitored the women during their sleep.

Results
During sleep, the top of the gel mattress was indeed about two degrees cooler than the top of a regular mattress. The temperature difference was greater during the first hours of sleep than in the later hours.

Click on the figure and tables below for a larger version.

The total sleep duration didn't increase as a result of sleeping on a cooler mattress, but the structure of the sleep itself did.

The total duration of deep sleep during a night on a gel mattress was almost ten minutes longer than when sleeping on a regular mattress. This equates to a 12 percent increase in deep sleep duration.

Recovery
In theory, an increase in deep sleep or slow wave sleep [another name for the same thing] could lead to better brain tissue repair, improved physiological recovery, a more effective immune system, better physical and cognitive performance, and improved mental health.

Sleeping on a cooler mattress lowered the heart rate at night by 1.6 beats per minute compared to sleeping on a regular mattress. This also indicates better recovery.