Photo/IllutrationIn Tokyo's trendy Shibuya, elated supporters converged upon the district's iconic pedestrian scramble after the final whistle at around 1 a.m., on June 29. (Takayuki Kakuno)

I have been sort of under the weather since last week, and I know why. This is the price I am paying for staying up well past midnight to watch World Cup soccer games on television.

I have attacks of overwhelming drowsiness during the day and suffer from lingering fatigue. I wish there were a prescription for “pro tempore night owls.”

Tsukasa Sasaki, senior researcher at the Ohara Memorial Institute for Science of Labor, which is known for its advanced labor- and sleep-related studies, noted, “Even if you stay up late two nights in a row, your body clock will readjust itself to some degree if you get back to keeping regular hours on the third day.”

This, Sasaki explained, is the reason why many companies designate every Wednesday as the “no overtime day.” Going home early on Wednesday mitigates the damaging consequences of putting in long overtime on Monday and Tuesday, he said.

The key to minimizing irregularities in one’s circadian rhythm is said to lie in what is known as “anchor sleep.”

Like a ship at anchor, even just a brief shut-eye at night can help restore the circadian rhythm. Specifically, Sasaki advised, taking a minimum two-hour nap between the hours of midnight and 4 a.m. should do the trick.

All these are good, practical tips. We have much to learn from the “sleep-related wisdom” of hospitals, factories, retail stores and other establishments where there are night shifts or night watch duties.

That said, however, sleep patterns have always varied among individuals throughout human history.

According to “Yume to Nemuri no Hakubutsushi” (Natural History of Dream and Sleep) by Takashi Tachiki, Leonardo da Vinci was one extreme case: He established his own unique pattern of resting for 15 minutes every four hours.

The other extreme was Albert Einstein, who slept solidly for 10 hours-plus every night. Anecdotally, he came up with his theory of relativity while lying in bed.

The more one researches sleep and awakening, the deeper the subject gets.

Although Japan has been eliminated from the World Cup in Russia, the games are nearing the climax. I intend to drop my “anchor sleep” firmly, and take in all the excitement that awaits.

--The Asahi Shimbun, July 5

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Vox Populi, Vox Dei is a popular daily column that takes up a wide range of topics, including culture, arts and social trends and developments. Written by veteran Asahi Shimbun writers, the column provides useful perspectives on and insights into contemporary Japan and its culture.