The Importance of Sleep

For most of us, sleep is something we take for granted. We look forward to it as a reward for a day’s hard work, time out from our ever-increasingly busy lives. In fact, we spend about a third of our lives sleeping…but we still know so little about it. Why do humans sleep? What purpose does it serve? And why does lack of it make us so distressed?

There are two main theories for why we sleep. One theory suggests that during wakefulness, the brain depletes its stores of certain chemicals such as proteins and cholesterol. Increased production of these and other “macromolecules” have been found during sleep, suggesting that shutting down allows the brain to restock essential energy reserves.

Another theory put forward more recently points to memory processing being a critical activity during sleep. We know that the brain is constantly dealing with vast amounts of incoming information. Experiences we have frequently – such as driving the car, reading, or everyday tasks we do at work – result in strengthened connections between neurones in the brain. That is, memory is formed when there are stronger synapses (the gaps between neurones), and these synapses form when we repeatedly engage in the same activity. If you like, it’s nature’s way of ensuring we don’t have to completely concentrate on every single little step needed to complete a task. The theory is that by shutting down our capacity to keep taking in new stimuli, the brain gives itself time to sort out those experiences that are meaningful and important, and “prune” those that won’t be needed in the future.

The next more common question is how much sleep do we really need, and what should we do if we’re not getting enough?

During sleep, our brains go through roughly four 90-minute cycles of electrical activity, each cycle repeated 5-6 times. Stage 1 is the “on-ramp” to sleep, a gradually lengthening of brain waves lasting 5-15 minutes. Stage 2 restores fatigued muscles and replenishes alertness, and is often disturbed with a feeling of falling or jerking muscles. Stage 3, lasting about 60 minutes, is “slow-wave sleep” and is associated with restoring levels of particular chemicals in the body such as growth hormones that repair bone tissue, and prolactin that regulates the immune system. Disturbances to this stage of sleep can have serious health consequences. And the deepest sleep is found at Stage 4 (REM or rapid eye movement sleep), which is dreaming sleep. Disturbances of this level of sleep affects alertness, concentration, judgement, and problem-solving.

Alarmingly, a recent review of 15 studies of over 470,000 people across 8 countries found that “short sleepers” – those regularly getting less than 5 hours’ sleep per night – significantly increased their risk of heart disease, diabetes, stroke and cancer. It’s still not clear why these risks are so dramatically increased, but one suggestion is that sleep deprivation disrupts the brains patterned tasks required as we progress through each sleep stage, and this causes disruptions to the immune system, thereby making us more at risk for other health problems.

Whilst there is still much to be learned about the brain and sleep, there are some simple take-homes messages:

  1. Aim to get at least 8 hours sleep every night; secondly, if you have to sacrifice this, aim for “power naps” targeted at Stage 2 sleep for as little as 3 minutes to refresh the brain. Focused relaxation techniques such as Mindfulness can help induce this level of sleep.
  2. Avoid caffeine and nicotine, or any other stimulants. It is best to avoid consuming any caffeine (in coffee, tea, cola drinks, chocolate, and some medications) or nicotine (cigarettes) for at least 4-6 hours before going to bed. These substances act as stimulants and interfere with the ability to fall asleep.
  3. Develop sleep rituals, things to remind your body and mind that it is time to sleep, and don’t take “active” rituals to bed. For example, taking your laptop to bed just to “finish off this last bit of work” in effect trains the brain to link bed with mental activity, and this is the opposite of what you want. Do some simple relaxing stretches beside your bed, flick through magazine or read something light, or listen to some calming music to prime the brain for rest.
  4. Physical activity throughout the day has consistently been linked to better sleep patterns. Unfortunately many of us have very sedentary lives and don’t move anywhere near enough for good health. Taking a walk in the evening, doing a workout, or simply spending more time on your feet (for example, replacing your office desk with a standing desk) all keeps the body more active.
  5. Change the physical environment at night to make it more natural. Some suggestion has been made that overhead lights are the worst thing for our brains at night because the brain interprets this as similar to sunlight, and stays alert. At night, turn off overhead lights and replace with lamps below eye level, and avoid screen-based devices for at least 2 hours before bedtime.

Dr Kate Lemerle

Published on February 8, 2016 by Kate Lemerle