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All in a night's sleep

All in a night's sleep

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What does your body do when your eyes close for the night? Rosie Brogan looks into the mysterious world of 40 winks.

One of the biggest myths about sleep is this: when our bodies drift off, our minds shut off. In fact, the brain is roughly 80 per cent activated during sleep. As Jennifer Ackerman eloquently explains in Sex, Sleep, Eat, Drink, Dream: A Day in the Life of Your Body: “Sleep is a remarkable journey of five stages repeated cyclically over the course of the night. These are richly varied states involving shifts in brain waves, body temperature, and biochemistry, in muscle and sensory activity, in thoughts and in level of awareness. Though the depth and quality of the journey may differ from person to person, from age to age, the pattern is more or less the same; four or five active cycles, each about an hour and a half long, alternating between quiet deep sleep and active REM sleep.”

Feeling sleepy?

Your body shepherds you through the evening, creating a ‘wake maintenance’ zone from around 6-9pm. Two or three hours later (unless you’re a chronic early riser), your circadian rhythms rev down and the brain’s pineal gland produces more melatonin, making you drowsy.

Stage 1 and 2 sleep

You stop hearing faint sounds and smelling lingering scents around you. As the University of Missouri describes it, these are relatively light phases sleep and “if someone is awoken during one of these stages, he or she will often report not being asleep at all.”

Stage 3 and 4 sleep

Not a lot of difference exists between these two stages, apart from the delta wave (high amplitude brain wave) content of each. These waves are associated with deep sleep, and there’s 50 per cent more of them in stage four—making it the most difficult stage from which to wake someone up, and the most likely stage during which you’ll sleep talk. It’s also the phase that allows for physical growth and development—so it’s especially important for kids.

REM sleep

No it’s not a rock band (well it’s that, too). ‘R.E.M’ stands for rapid eye movement and it’s characterised by sudden loss of muscle movement and dreaming (you can also dream during non-REM sleep, but it’s less vivid). Here, the eyes move rapidly under the eyelids, but no one seems to know why!

As the night wears on, you move from stage one to REM and then back up the scale again. Yet towards the end, the length of your delta sleeps decreases, until finally, you don’t delta sleep at all.

The alarm rings and you jump out of bed. Morning has broken.

Did you know?

Smoking can produce physiological changes that make it harder for you to get a good night’s kip. According to the American Journal of Epidemiology, a study on smoking and sleep architecture reports that smokers find it harder to fall asleep and also sleep more lightly when compared to non-puffers.

References available on request