long hours and sleep for only six or seven hours a night really do need that extra time in bed at weekends to stave off sleep deprivation.
The thesis that many people are chronically sleep-deprived is not without its sceptics, however. Yvonne Harrison and Jim Horne at Loughborough University have argued that we all have the capacity to sleep more than we usually do, but only in the way that we can carry on eating after our physiological need for food has been satisfied. In support of their sceptical position, Harrison and Horne have cited, for example, an experiment in which healthy young adults slept for up to ten hours a night for two weeks, getting an extra hour or so of sleep each night. This additional sleep produced some improvements in their reaction times and a slight reduction in daytime sleepiness. However, there were no significant improvements in the volunteers’ subjective ratings of their own mood or sleepiness.
Scientists are paid to be sceptical, and counterblasts are an essential part of scientific debate. Nonetheless, such arguments must be set against all the other strands of evidence showing that chronic sleep deprivation is a real and widespread phenomenon. We have considered some of that evidence and there is more to come. First, though, what about you?
‘… Are you going to bed, Holmes?’
‘No: I am not tired. I have a curious constitution. I never remember feeling tired by work, though idleness exhausts me completely.’
Sir Arthur Conan Doyle, The Sign of Four (1890)
There is no universal, one-size-fits-all figure for the right amount of sleep. Individuals differ considerably in their sleep requirements. The conventional standard of eight hours a night is somewhat arbitrary, though not far off the mark for most people. But the best yardstick for you is your own preferred sleep duration. You can measure this by conducting a simple, if time-consuming, experiment on yourself. You will need two weeks of complete freedom from the tyranny of work schedules and alarm clocks, which means you will probably have to wait until your next long holiday (and possibly much longer if you have small children).
What you do is this. Every night for about two weeks, go to bed at approximately the same time. Make a note of the exact time just before you turn off the light to go to sleep. Then sleep to your heart’s content until you wake spontaneously the next morning – not with the aid of an alarm clock. Note down the time when you woke up and, ideally, a more precise time for when you think you fell asleep the night before. (All being well, this should have been within 10–20 minutes of turning out the light.) Your time of waking should be when you first became fully conscious, not when you eventually stumbled out of bed. Then calculate how long you spent sleeping. The experiment will work much better if you do not roll over after waking and doze for a further hour or two before getting up.
Ignore the figures for the first few days, because you will probably be sleeping longer to compensate for your prior sleep deficit. We tend to feel sleepy on relaxing holidays and at weekends because reality has finally caught up with us; when the usual pressures and stimulation that keep us going through the working week are suddenly removed, we sleep more to catch up on the backlog. This extra sleeping is only transitory, however. Once you have caught up and reached equilibrium you should start to feel livelier and more energetic during the day. Unfortunately, by that time the holiday has usually ended and the normal regime of late nights and early mornings resumes.
After a few days, your nightly sleep duration should settle down to a stable figure. Take the average over the final few days: this represents your preferred sleep duration. It should be somewhere between seven and nine hours, although not everyone fits this pattern. Unless you are elderly or have an unusually relaxed lifestyle, your preferred sleep duration will probably be longer than the time you normally spend sleeping. If the difference is very large – say, two or three hours a night – you could be storing up serious trouble for yourself.
Why all this sleep? – seven, eight, nine, ten hours perhaps – with a living to make, work to be done, thoughts to be thought, obligations to keep, a soul to save, friends to refrain from losing, pleasure to seek, and that prodigious host of activities known as life?
Walter de la Mare, Behold, This Dreamer. (1939)
Another reason for believing that sleep deprivation is widespread is that we sleep less nowadays than our ancestors did. There has been a major shift in sleep patterns in industrialised nations over the past century, the net result of which is less sleep.
William Dement of Stanford University has argued that humanity is in the midst of a ‘pandemic of fatigue’. Dement estimates that people in industrialised countries now sleep on average an hour and a half less each night than they would have done a century ago, and that most of us consequently walk around with an accumulated sleep deficit of 25–30 hours. If true, this means we would have to sleep for an extra two hours a night for two weeks to clear the backlog and return to equilibrium. Some of us come close to doing just that when we take a two-week holiday.
Lifestyles in industrialised societies have altered radically over the past century in ways that have consistently eroded the status of sleep and dreaming, leaving many of us now probably sleeping less than at any other period in human history. We live in an era when many people work long hours, where we have vastly more opportunities for entertainment and leisure, and where sleep is widely regarded as the poor relation to other pursuits. Humanity has inadvertently created lots of reasons for not sleeping.
One reason for not sleeping is that there is always so much work to do. Many sectors of society now work longer hours, on more days, than ever before. In early nineteenth-century Britain there were some 40 days in the year when the Bank of England shut its doors to observe saints’ days and anniversaries. By 1830 the number of such holidays had dropped to 18 days a year, and nowadays there are fewer than ten. Not only do we spend longer at work, we also spend longer getting to and from work, as commutes have grown both in distance and duration. Time spent stuck in a car or public transport is time that cannot be spent in bed. Ironically, the technological revolution has failed to free us from the shackles of paid work. Quite the reverse, in fact – it has given us the wherewithal to work more productively all day, every day. James Gleick made the point beautifully in Faster, his glorious exposé of our no-time-to-lose society:
Marketers and technologists anticipate your desires with fast ovens, quick playback, quick freezing, and fast credit. We bank the extra minutes that flow from these innovations, yet we feel impoverished and we cut back – on breakfast, on lunch, on sleep, on daydreams.
Cheap mobile communications enable us to stay in touch wherever we are, 24 hours a day. Copious amounts of caffeine, the world’s most popular psychoactive drug, help to keep us awake as we squeeze ever more into the day. The puritan work ethic and the cult of time management nag us to do a little bit more at the beginning and end of each day. So we get less sleep. But that is stupid, because people who cut back on their sleep achieve less and feel bad into the bargain. They end up stumbling through the day, fatigued and underperforming, without even realising what they are doing to themselves. They become, to quote one scientific paper, borderline retarded.
The idea of being able to get by on little or no sleep might appeal to some driven souls who would rather use the extra time for other things. (Some people seem to find being at work easier than living a real life.) In J. G. Ballard’s short story ‘Manhole 69’, a scientist who has entirely expunged the need to sleep from three human volunteers sneeringly declares that:
