Turning up heat may be costing you sleep in winter
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As winter cold intensifies, many people respond by cranking up indoor heating. But sleep specialists warn that excessive warmth can be one of the biggest obstacles to a good night’s sleep, as it interferes with the body’s natural temperature regulation.
When room temperatures rise too high, peripheral blood vessels dilate excessively, preventing internal heat from being released. As a result, the body’s core temperature remains elevated, making it harder to fall asleep.
Core body temperature refers to the temperature maintained by vital internal organs such as the heart, lungs and liver. For healthy sleep, core temperature needs to drop by about 0.5 to 1 degree Celsius before bedtime. This cooling process also promotes the release of melatonin, the hormone that induces sleep. Overheating suppresses this natural decline, delaying the onset of sleep.
Experts recommend keeping indoor temperatures between 18 and 22 degrees Celsius, with humidity levels maintained at 40 to 60 percent. Sohn Yeo-ju, a professor of family medicine at Ewha Womans University Seoul Hospital, said, “When indoor temperatures are kept between 18 and 22 degrees, the body regulates heat most smoothly, allowing it to naturally enter a sleep-ready state.” She added, “If the room is too cold, however, the sympathetic nervous system becomes activated to preserve body heat, disrupting sleep continuity.”
Humidity control is just as important as temperature. When humidity drops below 40 percent, respiratory membranes can dry out, causing breathing discomfort during sleep. Levels above 60 percent, on the other hand, can encourage the growth of mold and dust mites, increasing allergy-related sleep disturbances and reducing deep sleep.
Adjusting daily habits can also help regulate body temperature naturally. Having a warm bath or foot soak at 38 to 40 degrees Celsius one to two hours before bedtime dilates peripheral blood vessels. Once you move into a cooler bedroom, heat dissipates more efficiently through the skin, allowing your core temperature to gradually fall and sleep to come more easily. Sohn said this method supports a healthier sleep rhythm than relying on artificial sleep aids.
To counter reduced melatonin production caused by shorter daylight hours in winter, experts advise getting sufficient natural sunlight during the day and avoiding exposure to blue light from smartphones and other digital devices at night. “The key to good winter sleep is creating an environment where core body temperature can decline naturally,” Sohn said. “When temperature homeostasis breaks down, both physical and mental rhythms are disrupted, so careful environmental management is essential to restore the body’s balance.”
This article from the Hankook Ilbo, the sister publication of The Korea Times, is translated by a generative AI system and edited by The Korea Times.