The cold wave that has brought sub-freezing temperatures to Kanto and other parts of Japan this week has no doubt led many to save on heating bills by retiring early and snuggling under their "denki mofu" (electric blanket).
But now Nikkan Gendai (Feb 4) has thrown a wet blanket on the notion that warm-as-toast bedding is a sensible way to hibernate. It says that humans, due to fewer hours of daylight during the winter months, naturally tend to sleep up to two more hours per night than they do in the summer. But should they have trouble sleeping at night, their biorhythm will become disordered, resulting in dysfunctional sleep that may even extend to the other months of the year.
Yohei Sugawara, an occupational therapist and author, advises readers how to improve their sleep. Essentially, he says, the greater the temperature that one's internal organs drops, the sleepier one will become, and the deeper one will sleep. In other words, once you fall asleep, if the internal body temperature continues to drop, and then the temperature starts rising in synch with the time to wake up, you will arise feeling well rested and invigorated.
"In order to reduce the internal body temperature, it's important to perspire and radiate heat," says Sugawara. "If bedding like an electric blanket that continually warms the entire body is used, then even if the body perspires, it becomes harder for the sweat to evaporate, and the body can't radiate heat. And because the internal body temperature doesn't drop, sleep tends to be lighter.
"Ordinarily a typical futon absorbs sweat during sleep, making it easier to radiate heat," Sugawara continues. "But electric blankets give priority to their mechanical heating function and are inferior in terms of ability to absorb sweat. Even if the blanket is only used to warm up the bedding when the sleeper first crawls into bed, it makes it more difficult for the internal body temperature to drop."
"In winter, activities by humans decline and their muscular power also diminishes," Sugawara adds. "Since the back muscles used to turn over in bed also weaken, the number of times we turn over during sleep also declines. But without turning over, air cannot be circulated between the futon and the body, making it impossible to radiate heat, and effective regulation of body heat ceases. To deal with this, people may keep the heat on in their bedrooms or put on heavier sleepwear, which makes it even more difficult for the internal body temperature to fall."
The most effective way to sleep in the winter is to devise ways to give priority to the parasympathetic nervous system, which functions when relaxing before bedtime. But in winter it becomes easier for the sympathetic nervous system to become active, and is difficult to reduce its operation before bedtime, making it harder to fall asleep.
To support the parasympathetic nerve function, Sugawara advises application of heat directly to the "senkotsu" (sacrum), a triangular shaped bone located at the bottom of the spine, just above the buttocks, where such nerves are clustered.
"First try holding a hot water bottle or thermal pack against the sacrum and then when you get into bed move the heat source to your feet," he suggests. "If you warm your ankles, the bottoms of your feet will radiate heat, causing the internal body temperature to drop, which should realize even better results."
Another suggestion is to set the timer on the heater to start warming up the room one hour before getting out of bed, so that the internal body temperature will gradually start to rise, thereby facilitating a natural process of awakening.© Japan Today