8 reasons to sleep 8 hours

Regardless of our determination to ‘need’ less sleep, so we can socialise for longer, exercise before work, watch more TV, I’ve been convinced by Matthew Walker’s captivating book ‘Why we sleep’, that the consequences of missing even an hour of sleep on the odd occasion can have more sinister effects than anyone has appreciated before.

What is sleep?

Contrary to historic beliefs, ‘sleep is not the absence of wakefulness’. Sleep is a complex, active and deliberate series of stages that the brain goes through every night. The three types of sleep (light Non-Rapid Eye Movement/ NREM, deep NREM and Rapid Eye Movement/ REM) all serve an array of different functions which means missing any of these types of sleep will cause impairment of the body and brain.

In an attempt to summarise the compelling evidence that Walker narrates in his book, here are the 8 reasons I’ll be getting into bed on time tonight.

1.      Learning and Remembering

Sleep is essential for forming new memories and preventing forgetting. The short term memory store (the Hippocampus) is temporary and has limited capacity. Sleeping overnight or taking a nap helps to move memories from this short term store into the larger long term storage site of the cortex whilst making more room in the hippocampus for new information.

The phrase ‘brain like a sieve’ really is true if you don’t free up short term memory by taking a snooze. Research shows that typically, sleep improves memory retention by 20 to 40% compared to the same time spent awake.

There is also evidence linking lack of sleep to Alzheimer’s although more research is needed to establish whether poor sleep is a contributor to the development of the disease.

2.      Muscle memory

Sleep helps us to master physical tasks such as playing the piano. Musicians often report struggling with a piece of music then waking up suddenly able to play with no problems. Research showed that compared to people who didn’t sleep between performances (they were tested in the morning and evening); people who slept (tested in the evening and next morning), showed a 20% increase in performance speed and a 35% increase in accuracy.

3.      Sports performance

Over 750 studies have been conducted on the relationship between sleep and human performance. Less than 8 hours of sleep and especially less than 6 causes an array of physical impairment including reaching physical exhaustion 30% quicker, impaired ability to cool down through sweating, decreased muscle strength, and significantly higher risk of injury.

4.      Heart attack and stroke

Adults over the age of 44 who sleep less than 6 hours a night are 200% more likely to suffer a stroke or heart attack in their lifetime. Combined with a culture of some of the world’s longest working hours, this figure rises to 500% in Japan.

5.      Cancer

A large European study of 25,000 people showed a 40% increase in the likelihood of getting cancer in individuals who slept 6 hours or less compared to those who slept 7 hours or more. Similar associations have been found across other studies including one with 75,000 women across 11 years.

6.      Weight gain and diabetes

There is a very strong correlation between lack of sleep and weight gain and the biology behind this relationship is proven. The less you sleep, the more weight you gain. Individuals who sleep less than 6 hours a night are also significantly more likely to develop type 2 diabetes.

7.      Starting a family

Men who sleep less than 6 hours a night have been found to have a 29% lower sperm count. Women with erratic working patterns that disrupt sleep are 80% more likely to have fertility problems shown in a study of 100,000 females.

8.      Drowsy driving

Sleepy drivers cause more deaths than drunk drivers and drug drivers combined.

The most common cause of sleep related car accidents is a momentary lapse in concentration called a microsleep. These can last just a few seconds during which the eyelid either partially or fully closes. During a microsleep your brain becomes completely unaware of the outside world and terrifyingly, you normally have no awareness that its happened. Your ability to act or react by braking or steering is momentarily ceased which depending on your speed of travel could result in an accident after just 2 seconds. Microsleeps occur in people who routinely sleep less than 7 hours a night.

A simple but clever experiment shows us just how severe these momentary lapses in concentration are, even in people who consider themselves good sleepers. Participants look at a screen and are asked to press a button every time a light is flashed. When given 8 hours sleep, people acknowledge almost every light. After one night of no sleep, people don’t slow down in their reactions, they miss the lights altogether. The number of lapses in concentration increases by 400%. Alternatively, after 4 hours sleep for 6 nights, the lapse in concentration is just as bad as if they’d missed a whole night.

Driving on less than 5 hours sleep increases your risk of a car crash by 3 times. Less than 5 hours and you’re 11.5 times more likely to be in an accident. The stats go on.

Although a drunk driver is slow in responding or braking, a tired person stops responding altogether.

The collection of research showing how poor sleep impairs every system in the body and brain, continues to grow. So put down your espresso martini and pick up an eyemask. It’s time to obsess about sleep.