"Since I've been staying home for a while because of the coronavirus, I'm no longer able to get up in the morning," a university student in Tokyo said with a wry smile.
She used to get up at 6 a.m. for the first class, work part-time from the evening and go to bed before the day changed. Even during spring break, her daily life did not change much as she had to attend brass band club activities in the morning.
However, due to the spread of the coronavirus, the club has been suspended since late February, and entrance to the campus has been restricted. This all allowed her to become idle, and she ended up watching online videos until about 3 a.m., chatting with her friends on the Line communication app and waking up at around noon. She became a night owl.
At her university, online classes started after the Golden Week holidays. The 20-year-old said she managed to wake up during class but said: "I'm spacing out in the morning and feel weird. I sometimes can't fall asleep at night. My life hasn't gotten back to normal."
Like this student, abnormal sleep rhythms caused by telework and school closures in response to the virus may be causing many people to feel unwell even after their daily routines return to normal, in what is referred to as "social jet lag."
"As in this case of people staying home, our biological clocks often become skewed during a long vacation, and the condition [of social jet lag] often occurs after people return to their lives after vacation," said Akita University Prof. Kazuo Mishima who specializes in psychiatry.
Our body temperature falls at night, with hormones that stimulate sleep rising, thus making us drowsy. During the day, our body temperature and blood pressure rise, and hormones that increase wakefulness are secreted, thus prompting us to be active. This circadian rhythm is controlled by our biological clocks, which are controlled by the suprachiasmatic nucleus in the hypothalamus of the brain.
Jet lag occurs when our biological clocks are not synchronized with when it is usually time to sleep.
"There is a social jet lag that many people experience in their normal lives but which is hard to notice, though it's not as big a gap as this time," Mishima said.
A typical example is staying up late and sleeping late over the weekend, when many people do not work.
Even a few hours' difference in the time you sleep or wake up between weekdays and weekends can cause fatigue and daytime sleepiness, reducing work and study performance. Hormone imbalance increases the risk of high blood pressure, diabetes and depression, and also is linked to the development of cancers such as breast cancer in women and prostate cancer in men.
Whether you have social jet lag can be checked by comparing the medial times of when you sleep and when you wake up on weekdays, and when you do them on weekends.
For example, if you go to bed at midnight and wake up at 6 a.m. on weekdays, but sleep at 2 a.m. and wake up at 10 a.m. on holidays, the median time is 3 a.m. on weekdays and 6 a.m. on weekends, meaning you have a social jet lag time of three hours. If you repeat this cycle, your biological clock will become skewed, throwing you into the same state you would feel as if you were traveling around India and Southeast Asia every weekend.
"If this lag is two to three hours, or more, you will get tired easily, and it will affect your mind and body," said Kurume University Prof. Naohisa Uchimura who specializes in neuropsychiatry.
Unlike temporary jet lag caused by overseas travel, social jet lag, which is repeated on weekends, has a long-term effect, and the greater the degree of the time lag, the higher the health risk becomes.
An international survey of 150,000 people found that 30% of them had more than two hours of social jet lag.
"The key is to get up at the same time in the morning and be exposed to the morning sun even if you go to bed at a different time," Uchimura said.
If you still feel drowsy, Uchimura advises to keep the time you wake up on weekdays and holidays within two hours, or take a nap lasting 20 to 30 minutes before 5 p.m.
Read more from The Japan News at https://japannews.yomiuri.co.jp/
