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BOUND TO PLEASE / Did you get 8 hours of therapy last night?

The Japan News

By Tom Baker / Japan News Staff WriterWhy We Sleep: Unlocking the Power of Sleep and Dreams

Matthew Walker

Scribner, 360pp

“How wonderful is Death, / Death and his brother Sleep!” So wrote poet Percy Shelley 200 years ago. Today, scientist Matthew Walker has a different take on the subject: “the shorter your sleep, the shorter your life.”

Walker is a professor of neuroscience and psychology at the University of California, Berkeley, where he directs the Center for Human Sleep Science.

In “Why We Sleep,” he shines a light on the mysterious hours of unconsciousness we experience each night. Various studies, many of which involve measuring the brain activity of sleeping volunteers, reveal important things happening behind our closed eyelids.

For example, the brain transfers recently acquired knowledge from short-term memory to long-term memory while we sleep. This saves the things you want to remember, and makes your decluttered short-term memory more receptive the next day.

You may know the phase of sleep in which we dream is called rapid eye movement (REM). But did you also know dreaming de-links memories of traumatic events from the emotions that accompanied them? This lets us remember the worst days of our lives without reliving their terror or grief. The nightmares that are part of post-traumatic stress disorder indicate this system has broken down — an insight that helped Walker contribute to developing a treatment for that aspect of PTSD.

REM is also the time when new connections are made among brain cells. This is especially crucial for unborn babies, whose developing brains spend a huge amount of time in REM, peaking at 12 hours a day in the last two weeks before birth.

Walker warns that alcohol strongly suppresses REM, which is one reason expectant mothers should avoid it. It also explains why severe alcoholics may experience hallucinations called delirium tremens. The brain’s need to dream, if suppressed too often, begins to assert itself during waking hours.

Non-REM sleep, or NREM, has its own benefits, including improvements in motor skills learned during the day. Also, fluid bathes the brain during NREM, flushing out toxins that include amyloid protein, the buildup of which is associated with Alzheimer’s disease.

Walker advises athletes to get plenty of sleep before a big event — and after. “Post-performance sleep accelerates physical recovery from common inflamation, stimulates muscle repair, and helps restock cellular energy.”

This advice is not just for athletes. Walker cites a Japanese study that found students who sleep more get better grades. Another Japanese study found workers who sleep less have more cardiac arrests.

He also cites a study measuring the economic cost of sleep loss. Japan’s figure is the worst of several listed, at 2.9 percent of GDP. As a recent Yomiuri Shimbun editorial noted, “Japan’s labor productivity per hour is among the lowest of major countries.” Maybe the answer is shorter working hours and longer sleeping hours.

This fascinating book explains circadian rhythms, jet lag, the effect of caffeine, drowsy driving and much more. Walker describes so many ill effects of sleep deprivation, a modern epidemic, that he concludes with a statement that might intrigue Shelley: “lack of sleep is a slow form of self-euthanasia.”

On the bright side, if this book inspires you to get eight hours of sleep at night, you can start each day with the gratifying knowledge that you’ve already accomplished something.

Where to Read

Anywhere but in bed. Turn off the lights and drift away.

Maruzen price: ¥4,614 plus tax (as of Feb. 16)Speech

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