BACK in the 1960s, the contraceptive pill unshackled sex from human nature. Could a new class of tablets be about to do the same for sleep? Introducing CX717, a drug being developed by Cortex Pharmaceuticals of Irvine, California. It's the first of what promises to be many aimed at detaching people from the daily routine of eight hours each for work, rest and play.

Tests conducted on rhesus monkeys last year suggest that CX717 can wire users to remain awake for 36 hours without the jitters, euphoria and eventual crash that come after mega-doses of caffeine or amphetamines. Further down the line are even more radical compounds—stimulants that can wipe out sleep for several days at a stretch, and pills that deliver a whole night's shut-eye in two hours.

Prompted by some energetic marketing on the part of drugmakers, scientific journals are already ablaze with excited talk of “conquering sleep”, asking whether humans will become the first species to dominate both daytime and night-time. The commotion, however, raises the more pertinent question: how much sleep do we actually need?

Lux eterna

Before the advent of the electric lightbulb, it wasn't much of an issue—people hit the hay after a couple of hours by candlelight, and stirred at daybreak. But the invention of artificial lighting, and the subsequent introduction of shift working, has progressively “detached us from the 24-hour cycle of light and dark,” says Russell Foster, professor of molecular neuroscience at Imperial College, London.

Today, our culture of long hours at work and the 24-hour availability of almost everything from convenience stores to television and e-mail have demoted sleep in our priorities. To manage fatigue, says Dr Foster, “we've fallen into a stimulant-sedation loop, where stimulants such as caffeine and nicotine are used for wakefulness during the day and sedatives such as hypnotics and alcohol are used at night to induce sleep.”

The eight-hours mantra has no more scientific basis than the tooth fairy.

That has compressed the sleep cycle. A report published last year, entitled “Insomniac Britain”, by the British Association for Counselling and Psychotherapy found that adults in the United Kingdom sleep an average of six hours 53 minutes each night. Is that enough? Not according to the ancient formula of eight hours of rest, eight hours of work and eight hours of play, which many physicians and therapists still swear by. And it's not enough for the survey respondents, many of whom considered themselves “sleep-deprived”.

But a new, contrarian school of thought is emerging. The eight-hours mantra has no more scientific basis than the tooth fairy, says Neil Stanley, head of sleep research at the Human Psychopharmacology Research Unit at the University of Surrey in Britain. He believes that everyone has their own individual “sleep need” which can be anywhere between three and 11 hours. “If you're a three-hour-a-night person, you need three; if you're 11, you need 11.” To find out, he says, simply sleep until you wake naturally, without the aid of an alarm clock. Feel rested? That's your sleep need.

Core sleep beats deep sleep

The global get-to-sleep industry—pills, lotions, “no-turn” mattresses, foam “memory” pillows and the like—has conditioned us to think we're not getting enough, adds Jim Horne, director of the sleep research centre at Loughborough University in Britain and author of the new book, “Sleep Faring: A Journey through the Science of Sleep”. What really matters, he says, is the “core” sleep, the first few hours that nourish the higher sections of the brain. Anything beyond that—including deep REM (rapid eye movement) sleep—is “non-essential” and taken for pure pleasure. Consider the domestic cat: feed it well, and it sleeps a lot; withdraw the food, and it's out hunting.

As long as you're not a zombie the next day, you're probably sleeping enough, says Dr Stanley. He appeals to the concept of “non-restorative sleep” recently put about by the German Society of Sleep Research and Sleep Medicine. In Germany, there has been a shift in emphasis: traditionally, treatment focused on reducing sleep “latency”—the interval between settling in for the night and the onset of sleep—and thus prolonging total sleep time. Now, the focus is on restoring the recuperative value of sleep and ensuring daytime functioning on a social, psychological and professional level.

In truth, however, no one really knows whether ten hours a night is any better than five. The science of sleep has not advanced an awful lot since 1834, when the first book in the English language on the subject—“The Philosophy of Sleep” by a Glaswegian physician called Robert MacNish—was published. Of course, we can now plot brainwaves, track hormones and add new taxonomies to the International Classification of Sleep Disorders (89, at the last count).

We can link sleep problems to driving and industrial accidents; to a higher rate of divorce; to increased risks of heart disease, breast cancer, diabetes, colo-rectal cancer and obesity. We're also confident of the role of sleep in reinforcing memory, learning and cognitive performance. But the real fundamentals—such as why we sleep, and why some people can function on less than others—elude us.

Used infrequently, drugs such as CX717 might be a handy standby for the odd occasion when—for whatever reason—you absolutely, positively, have to stay awake. But talk of banishing sleep for ever is “spectacularly naive,” says Dr Foster. “We don't understand the physiology of sleep, but we seem happy to regard it as something to ‘cure' and then throw away.”

Cortex Pharmaceuticals provides more information on CX717. “Insomniac Britain” is available online. America's National Sleep Foundation and Sleepnet.com offer tips on getting a good night's rest, information on sleep disorders and more.