Insomnia is now Japanese national disease

Sleeping hours Japanese people daily take are one of the shortest in the world. An international comparison of sleeping hours made public by the Organization for Economic Cooperation and Development (OECD) in 2009 revealed that Japanese sleep for seven hours and 50 minutes per day on average, which was shortest along with that of South Koreans. However, according to an article published in October 2015 by The New York Times, Prof. Jerome Siegel and his colleagues at the Semel Institute for Neuroscience and Human Behavior at University of California Los Angeles (UCLA) found in their new study that sleeping hours and insomnia have no correlative relationship. Then, what is the cause of sleep disorders such as insomnia?




To begin with, insomnia is a condition where people develop some health troubles such as daytime sleepiness, distraction or fatigue after a spate of symptoms like having difficulty falling asleep at night or keeping asleep, awakening too early in the morning or sleeping too shallowly to feel satisfied. According to a study by the Japan Preventive Association of Lifestyle-related Disease (JPALD), about one in every five Japanese is annoyed with those symptoms. We may say insomnia is now one of Japanese national diseases.




Prof. Siegel’s team researched the sleep patterns of three different hunter-gatherer tribes (two in Africa and one in South America) who live in industrially undeveloped areas and found that these people sleep six and a half hours per night on average. While 20% of Japanese adults suffer from chronic insomnia according to JPALD, the U.S. team found that the ailment occurred in only 2% of the hunter-gatherers. The sleep patterns of the three tribes were found to be so similar to each other that Prof. Siegel surmised, “This is how all our ancestors slept.” Surprisingly, any word meaning insomnia did not exist for two of the three groups. This seems to suggest that there is no correlation between the amount of sleep and insomnia. Prof. Siegel’s team thinks that the fall of ambient temperature might have sent a signal urging the human body to take sleep. Its research found that all the three hunter-gatherer groups almost always fell asleep as temperatures began to fall at night and woke up as the temperatures were rising again. This suggests that humans may have evolved to sleep during the coldest hours of the day, perhaps as a way to conserve energy, Prof. Siegel said.




The popularization of heating and cooling equipment such as air-conditioners and electric carpets, which did not exist before the industrial revolution, has brought dramatic changes to the living environment. Moreover, it is pointed out that blue light emitted from computers and smartphones causes eye fatigue and awakening effect that can lead up to insomnia. Can’t we say that the industrial development brought by electronic devices such as blue light-emitting laptops and smartphones is largely to blame for our sleep problems?(Written by Yuto Yawta)





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