Ancient Japanese poetry is full of sleeplessness. So is modern life. The ancients needed no sleep doctors, sleep scientists or sleep consultants — as we do — to explain and cure their wakefulness. They knew the cause only too well — love-longing. The cure was obvious, though not always within reach.

President magazine last month titled an extended feature on sleep “The Sleep Revolution.” Japan needs one. It sleeps very badly.

Love, strangely enough, draws only a passing glance — rather a cold one, the emphasis on hormones rather than emotions. Physiology comes more naturally to us than poetry. Instead of love eroding sleep, we say sleeplessness erodes love. President recalls a 2005 study by the condom-maker Durex that calculated for sleep-deprived Japan an average 45 per capita couplings per year — a third fewer than Greece, the world leader.

South Africa leads the world in sleep. An OECD survey ranks it first among 30 nations in minutes of sleep per night, 553. China is second with 542, America seventh with 528, Spain 11th with 516, Germany 24th with 498 and Japan last with 442.

Eros is implicated but not central. Sleep deficiency is too broad a problem for a single culprit. Contributing factors are legion. Modern life itself must stand trial. It does. Charges dismissed — other modern nations, on the evidence, sleep well enough. What drives sleeplessness in Japan? Japan’s ways of coping with modern life. They won’t do, says President.

Masashi Yanagisawa, director of the Tsukuba University-based International Institute for Integrative Sleep Medicine, writes in President of European colleagues’ astonishment when visiting Japan at a sight so common here it passes all but unnoticed — people sleeping on trains. Europeans don’t, it seems. Maybe, the visitors speculate, it’s a reflection of how safe Japan is. No, says Yanagisawa — of how tired Japan is.

Japanese who make a virtue of exhausting themselves and their subordinates at work are misguided, Yanagisawa says. He cites a 2016 Rand Corporation study: mental sluggishness resulting from sleep deficiency costs the economy roughly 3% of gross domestic product — in Japan’s case, ¥15 trillion a year.

The quality of our sleep depends on the quality of our wakefulness. This is so self-evidently true — whether “quality” is measured in socio-economic terms as productivity or in personal terms as happiness — that mass sleep deprivation must rank among a society’s more colossal failures.

Sleep grows ever harder to snuggle up to. Life no longer conduces to sleep. It itself never sleeps. It’s awake 24/7 — and seduces, distracts and entices us into suppressing our weariness and keeping it company. There’s so much to do, and only so many hours in the day. That’s true everywhere but Japan is conspicuously immoderate in robbing the night of its due. It turns more of night into day than other nations do. Night takes its revenge.

It attacks on two fronts: exhaustion and disease. Diseases linked to sleep deprivation run the gamut — depression, cancer, dementia. The immune system suffers, with sinister implications in a time of plague. The links are vague and expressed in percentages. As an individual you may escape the worst. Why run the risk? Because risk is inherent in all striving and most pleasure. Well, it’s up to you.

Sleep rebuffed rebuffs in turn. The night owl begins by disdaining sleep and ends insomniac — unable to sleep. Surveying 500 businesspeople aged 20 to 69, President found 74.2% claiming sleep trouble. It runs across the age spectrum: 77% of those in their 20s, 83% of those in their 30s, 63% in the 60s. Waking from a bad night leaves you bleary of eye and equally so of mind — say 70% in their 20s and 95% in their 30s. No fewer than 87% in their 20s, 83% in their 30s and 75% in their 40s and 50s feel sleepy during the day. This is what visiting Europeans see when they ride Japanese trains.

What’s to be done? For those who like that kind of thing, there’s gadgetry galore — “sleep trackers” that measure and dissect your sleep in terms of heart rate, brain waves and so on. Sleep consultant Nao Tomono, a sports health researcher based at Juntendo University, doesn’t mention these in her contribution to President’s feature. Her “sleep lessons” stress a more naturalistic approach.

Bananas are good, avocadoes likewise — both rich in protein. Power naps are OK but not after 3 p.m. Don’t sleep on trains. Body temperature, room temperature, room lighting, background music all come into play. Regulation will vary with individual taste but not beyond upper and lower limits. Woo sleep with care and it will respond.

The question arises: why not simply pop a sedative? It’s an option, but merits caution. Dependency and unknown long-term side-effects are the risks. Consult a doctor, weigh the odds, and make your choice.

“To sleep, perchance to dream,” said Hamlet. Not “perchance” — inevitably, says President. We dream on average four dreams a night. A dreamless sleep is a night of forgotten dreams. Remembered dreams sent our ancestors to prophets, diviners, fortune-tellers. Today we consult scientists, as President does Kyoto University psychologist Toshio Kawai. A dream of a snake may mean a pending shedding of skin — a life change, in other words. Children often dream of being able to fly; adults, of losing that ability. In an adult it suggests coming to terms with reality, experienced mostly as friction.

Lastly — for how better to conclude a discussion of sleep than with the most fundamental question of all — what is sleep? Answer: We don’t know. We know it when we experience it, or at least — since asleep we know nothing — when we wake from it. But definition eludes us. Will artificial intelligence need sleep? Will worries keep it awake? Will wakefulness affect its sanity? “Sleep science” has barely scratched the surface.

Michael Hoffman’s latest book is “Cipangu, Golden Cipangu: Essays in Japanese History.”

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