(Updates with study participants in eighth paragraph.)
Oct. 19 (Bloomberg) -- Tokyo office workers slept at least 30 minutes less than their counterparts in New York, Paris, Shanghai and Stockholm each night, averaging six hours, or 14 percent less than the recommended minimum, a study said.
Workers in Tokyo went to bed at 12:18 a.m. on average, according to the joint study by Stanford University and Ajinomoto Co., a Japanese foodmaker that sells a sleep supplement called Glyna. The U.S. National Sleep Foundation recommends seven to nine hours a night.
The study was presented at a meeting of the World Sleep Federation in Kyoto today along with other research that highlighted sleep deprivation among Japanese. A separate study presented at the forum found an “extremely serious” lack of sleep among middle-school students in Japan.
“Most of the people in Tokyo are sleep-deprived,” said Makoto Bannai, a senior researcher at Ajinomoto, which sponsored the study. “They need to know better sleep can bring more efficiency to daily activities.”
The office-worker study found that people in Tokyo got 36 minutes less sleep than New Yorkers and 54 less than Parisians. Only 23 percent of Japanese got more than seven hours of sleep, it said.
The study surveyed 180 men and women from each of the five cities, who were 30 to 60 years old. They attributed their sleep trouble to work and personal stress, outdoor noise and the weather, among other reasons.
A study presented by Kyoto Prefectural University found that Japanese middle-school students slept an average of 6.9 hours a night. Teens need more than nine hours a night to function best, according to the Arlington, Virginia-based National Sleep Foundation.
The research involved 1,545 middle school students who were 12 to 15 years old at 13 public schools in Kyoto, western Japan.
--Editors: Nicholas Wadhams, Terje Langeland
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