How much sleep do we need – when – and why?

 

Around a third of the population have trouble sleeping, including difficulties maintaining sleep throughout the night, particularly those who work unusual hours like shift workers. While night time awakenings are distressing for most sufferers, there is some evidence from our recent past that suggests that we had two periods of sleep each day and a period of wakefulness occurring between two separate sleep periods was the norm.

snoring and apnea

Segmented sleep is well documented across time, ranging from medical texts, to court records and diaries, and even mentioned in Charles Dickens’ book, Barnaby Rudge, which was written as late as1840.

References to the first and second sleep started to disappear during the late 17th century. This is thought to have started in the upper classes in Northern Europe and filtered down to the rest of Western society over the next 200 years and interestingly, the appearance of sleep maintenance insomnia in the literature in the late 19th century coincides with the period where these accounts of split sleep start to disappear.

Today’s society often doesn’t allow for this type of flexibility as we have to conform to today’s sleep/wake schedules, and it is generally thought that a continuous 7-9 hour unbroken sleep is probably best for feeling refreshed.

Some of the key advantages of a split sleep schedule include the flexibility it allows with work and family time, and some individuals in modern society have adopted this type of schedule as it provides two periods of increased activity, creativity and alertness across the day, rather than having a long period where tiredness builds up across the day and productivity wanes.

There are implications in this for shift workers and split sleep schedules have recently begun to emerge with some employers as a potential alternative to continuous night shift work. Some industries have introduced schedules with shorter, but more frequent shifts, so that the drive for sleep will be less with reduced time. While the challenges of night shift work cannot be fully eliminated, the advantage of some split shift schedules is that all workers get at least some opportunity to sleep at night and do not have to sustain alertness for longer than six to eight hours – much safer.

There is no tradition of an afternoon rest, like the Spanish siesta, in many countries. However some of the greatest statesmen, philosophers, writers and artists were habitual ‘nappers’ so perhaps there is a basis for it. Winston Churchill was devoted to his afternoon nap, which he called ‘that refreshment of blessed oblivion’. Henri Matisse napped after lunch, Thomas Mann for an hour before tea, and P.G. Wodehouse for an hour afterwards.

There are both mental and physical benefits to napping. A study last year published in the International Study of Behavioural Medicine, found that students who had a catnap of no longer than an hour had significantly lower blood pressure when faced with a complicated mathematical problem than those who had not slept. The study concluded that daytime napping may have a positive effect on cardiovascular health.

Another study last year, done in Germany, found that napping also helped with memory function. Participants had to learn lists of 90 single words and 120 unfamiliar word-pairs such as milk-taxi. Half were then allowed a 45–60 minute nap, while the other half watched a DVD. When it came to remembering the words, the nap group accurately remembered five times as many words and word-pairs as the DVD group. The study concluded that a short nap after a concentrated period of learning ‘plays an important role in memory consolidation’.

A NASA study of military pilots and astronauts, whose jobs are disrupted by their natural sleep cycles, worked out that the ideal length of a nap was 26 minutes and this improved performance by 34% and alertness by 54%.

On the other hand many people think they can teach themselves to need less sleep, but they are wrong, says Dr. Sigrid Veasey, a professor at the Centre

for Sleep and Circadian Neurobiology at the University of Pennsylvaniaʼs School of Medicine. “We might feel that we are getting by fine on less sleep, but we are deluding ourselves, largely because lack of sleep skews our self-awareness. The more you deprive yourself of sleep over long periods of time, the less accurate you are of judging your own sleep perception,” she said.

In support of this, Health issues like pain, sleep apnea or autoimmune disease can increase people’s need for sleep, said Andrea Meredith, of the University of Maryland School of Medicine.

 

John Redfern