Sleep is not only controlled by the brain’s “sleep drive.” It is also guided by body temperature. Across the day, the body runs on a rhythm: temperature is generally higher during active hours and drops as the body prepares for sleep. That drop is not just something that happens after someone falls asleep. Evidence suggests it is part of the setup process that makes sleep easier to start. This is where heated blankets and other warming sleep products fit in: they can change how heat moves through the body right at bedtime.

A key piece of the science is that falling asleep is closely linked to the body letting heat escape through the skin—especially through the hands and feet. In a controlled laboratory setting, researchers tracked a simple signal: the temperature difference between the skin at the hands/feet and the skin closer to the body’s core.

This “heat-loss” signal was the strongest predictor of how fast people fell asleep, stronger than core temperature itself, heart rate, the start of melatonin release, or how sleepy someone said they felt. The interpretation is straightforward: when blood vessels in the hands and feet open up, the skin warms there, heat leaves the body more efficiently, and the brain seems to accept that as a “time to sleep” cue.

A review that combined results from several similar controlled studies reached the same conclusion: this heat-loss pattern is one of the best predictors of sleep onset. It also noted that “lights out” and relaxation often come with a quick shift in body heat toward the skin and a drop in heart rate, and that these changes happen before sleep begins.

That’s where heated blankets can be surprisingly logical. Warming the skin—if it is mild and comfortable—can help trigger the same kind of heat shift. One study used a temperature-controlled suit to slightly increase skin temperature during the night without changing core temperature. The increase was tiny (about 0.4°C at the skin), yet it had large effects: less wakefulness at night and a shift toward deeper sleep, in both young and older participants.

The biggest changes were seen in older adults and people with insomnia. In older subjects, the mild warming almost doubled the share of deep, slow-wave sleep and sharply reduced early morning awakening risk in the experiment. Brain-wave recordings also showed stronger low-frequency activity, which matches deeper sleep.

Importantly, this is not saying “hotter is better.” The benefit came from subtle warming, not overheating. The wider sleep-temperature literature helps explain why. During sleep, the body’s ability to handle heat and cold changes, and different sleep stages do not regulate temperature in the same way. Reviews describe that sleep normally comes with lower core temperature, reduced muscle activity, and changes in automatic nervous system control that help release heat through the skin.

Warming the skin can push the system toward a sleep-friendly state, but too much heat can become uncomfortable, fragment sleep, or cause sweating that wakes someone up. The most evidence-backed idea is that comfortably warm skin supports sleep onset and depth, while maintaining a stable, not-stuffy bed climate.

Overall, the science behind heated blankets is less about “cozy vibes” and more about physiology. By gently warming the skin, especially around bedtime, the body may more easily shift heat outward and settle into the temperature pattern that normally accompanies sleep.

The strongest benefits in controlled studies appear in older adults and those with more fragile sleep, which is consistent with age-related changes in temperature regulation.