The night: Why they call it the graveyard shift

 作者:福去     |      日期:2019-03-01 01:07:03
By Tiffany O'Callaghan It’s not just emergency workers who endure perma-lag (Image: Ken Schles/Gallery Stock) Read more: “The night: The nocturnal journey of body and mind“ SOMETIMES, there just aren’t enough hours in the day. Most of us have pulled an all-nighter at one time or another. There are even those who make a habit of it: Thomas Edison reputedly worked without sleep for days on end when in the throes of invention, as did his arch-rival, Nikola Tesla. But for most of us, pushing on past bedtime takes real effort. Our body’s master clock – a collection of about 50,000 neurons in the brain’s suprachiasmatic nucleus – responds to external cues, such as light, and coordinates the cellular clocks in our organs and muscles. It influences the rhythms of our autonomic system and spurs our endocrine system to secrete hormones associated with everything from sleepiness to stress – and it is extremely hard to ignore. “That’s why shift workers find it difficult to get enough sleep – during the day, the biological clock is promoting wakefulness,” says Christopher Morris, a researcher in sleep medicine at Harvard Medical School. Imagine jet lag as a way of life and you get the idea. It is not just security guards and emergency workers who have to endure this perma-lag. One in five US employees works shifts that fall at least partly outside the hours of 6 am to 6 pm, and 1 in 15 works late shifts exclusively. Many people involved in global markets log on outside normal office hours. And yet more simply keep beavering away long after the sun goes down: