Sleep expert reveals exact amount of sleep you need at your age

Want to know why you feel tired so often? Because you’re not getting the right amount of quality sleep - check the chart to see how many hours a night you should be getting.

Our brain operates continuously, day and night, for every day of our lives.

As it goes about its 24-hour cycle, it switches functions to accommodate our changing needs – and one of the most important of those needs is sleep.

It’s an activity that occupies about one-third of our lives.

For many of us, it feels quite simple. When we get tired, we shuffle off to bed and go to sleep for the next seven to eight hours (or for some of us considerably less than that). But in many ways its purposes remain a mystery to us.

And the more that neuroscience – the study of the brain – uncovers, the more scientists have come to understand just how complicated a process it is.

Better sleep leads to better health.

Over the past five years I’ve lectured on sleep to students and staff at many universities on behalf of a major health insurer. You might ask – quite reasonably – why would an insurance company invest so heavily in an area like sleep?

The answer is a simple one: better sleep strongly correlates with better health, and better health means better business. The health effects not just of illnesses such as insomnia and sleep apnoea but also of poor or insufficient sleep are front and centre in the minds of the insurers, and increasingly in the minds of the rest of us.

In my lectures, one of my young students will almost inevitably explain away their constant studying and partying with the words: “Plenty of time to sleep when I’m dead.”

I hear similar things from hardworking executives, who claim that they’ll get all the sleep they need when they finally shuffle off this mortal coil we call life.

Ironically, death may catch up with all of these people far more quickly than they think. Put simply, extreme lack of sleep can kill, as chronic fatigue increases our risk of disease, illness and early mortality.

Both these groups have failed to understand the true significance of sleep.

As far as they’re concerned, it’s not something that needs to be focused on, let alone something that could be improved, even to the point of excellence. Why do so many of us have an acute awareness of other aspects of our health, but see sleep as something that “just happens”?

Sleep is an essential pillar of good health and needs to be taken seriously and prioritised.

I want to show you what happens when sleep is done right, and what can occur when it goes wrong. And I want to explain why. I want to persuade you that adequate sleep is essential for the health of our entire body and brain, and that we require both sleep quantity and sleep quality.

Both sleep quantity and quality are important.

Excellent sleep occurs when we get both.

But what about those of us who would desperately love to get those seven to eight hours’ sleep a night, but can’t? Maybe you suffer from a health complaint or sleep disorder, maybe your job means you sleep irregular hours, or perhaps you just can’t stop thinking about the events of the day when you turn out the lights at night.

Sleep and relaxation are so important to our overall wellbeing, but increasingly difficult to achieve in our digitally based, fast-paced, time-poor and stress-filled world.

For the vast majority of us, sleep is something we don’t think about until we have to. But ask anybody, “How was your sleep last night?” and the answer is almost always: “It could have been better.”

So why not work on making it better? Why not work towards being able to say, “I had an excellent sleep”?

If we start to look at sleep as a 24-hour process, and not just a waste of seven to eight hours, we can then begin to link the activities of our wakeful periods to our sleep periods and give ourselves a real chance of achieving an excellent sleep.

THE PURPOSE OF SLEEP

How sleep happens, and what’s going on while it happens, are complex questions, and yet at face value very simple. Sleep literally involves doing nothing but lying down and not being conscious.

The purpose of sleep is a very hot topic, widely debated among scientists. Clearly, sleep is for rest, which allows our body and brain time to recover and recharge. Periods of activity that leave us feeling exhausted need to be followed by prolonged periods of inactivity to give our system time to recover and be replenished.

Go to sleep.

But sleeping is not just resting. The amount of sleep we need is not dependent on the amount of activity we’ve engaged in.

We can usually sleep around seven hours whether we have completed hard manual labour or lain around on the lounge all day. One activity requires recuperation and the other does not, which is why exhaustion does not dictate our sleep patterns. As we’ll see, the timing and duration of our sleep are determined not by our need to rest but by our body’s circadian rhythm, our biological clock.

Our body temperature drops by one or two degrees during sleep, which suggests that sleep is about more than just resting and conserving energy. When animals hibernate, both their metabolism and their temperature drop to an almost comatose state, during which they move in and out of sleep. This process uses an enormous amount of energy and confirms just how complicated sleep is. Seeing it as simply about resting and re-energising is very much underestimating sleep.

Sleep’s role in physical healing and defusing negative emotions is well documented. But more recently, scientific theories have focused on sleep’s ability to remove weak neurological connections and improve brain function.

SLEEP AND BRAIN PERFORMANCE

Believe it or not, sleep can actually help us become more intelligent and develop better problem-solving and decision-making skills, reasoning and judgment.

The act of learning involves a highly efficient ability to remember information. If we learn something before going to sleep, or even having a nap, the brain replays that information many times while we sleep.

We’ll wake up remembering it better than before we went to bed. The process begins when we take information that we captured with our five senses, then temporarily store it in our brain’s memory-holding tank, called the hippocampus.

Sleep affects our ability to learn and make memories.

Processing this information requires us to transfer it to the outer layer of the brain, the cortex. The cortex then proceeds to consolidate (choose what is important and discard what is not), edit (rearrange and restructure), and file what we’ve learned into our long-term memory until we need to retrieve it again. This is called long-term potentiation. Connections between relevant neurons (nerve cells) are strengthened, including memories.

Meanwhile, to avoid overactivity and optimise energy use, less important connections are weakened or removed. This means that when we are awake, significant connections will become stronger.

Our old memories must be connected to our new ones to help reinforce learning and, most importantly, improve accessibility. Our very old memories regularly need to be stimulated, so that the connections, and the memories attached to them, are not lost. This same process also takes place when we develop new skills. It goes on during sleep because it’s the most efficient time for the brain to do it. There are no distractions, and no new information is demanding attention.

It’s been found that different types of memories are consolidated during different stages of sleep. If we wake in the second half of the night, when most of our dream sleep occurs, we don’t consolidate learned motor skills. If we wake early in the night, we may lose our verbal learning. During deep sleep, our brain is actively carrying out the task of converting fresh experiences into long-term memories.

In dream sleep, an area of the brain called the associative cortex is particularly active. This allows us to come up with new and useful ideas, link concepts and thoughts in novel ways, or simply tap into our creative process.

Our brain continues to work on problems that baffle us, and it may come up with the right answer only after we’ve rested. Only in the dream phase of sleep is our brain capable of carrying out this process, and it’s mostly during this stage that our brain reinforces, organises and maintains our “memory files”.

Sleep also provides an opportunity for the brain to remove information and a wide variety of by-products that it doesn’t need. The complex ongoing cellular activity of the brain produces material that needs to be treated as waste and removed. While this occurs all the time, during sleep the brain is particularly active in its waste management.

Stan Rodski’s new book on sleep.

WHEN SLEEP GOES WRONG

When sleep goes right, our brain is successfully acquiring new information and finding creative solutions through our dreams. When sleep goes wrong – either we don’t get enough, or it’s poor in quality – there can be a whole array of consequences, both short- and long-term.

How much sleep do I need?

Our sleep requirements vary considerably throughout our lifetime. Although there is no magic number of hours that guarantees a satisfying slumber, the graph opposite is a good general guide to sleep needs across our lifespan.

As it shows, sleep is especially important to children as they rapidly acquire and reinforce learned information.

Infants sleep more than half the day, with extended periods of dream sleep, to optimise brain efficiency. Our sleep needs tail off as we reach adolescence, then are further reduced in the final few decades of life.

Depending on your age, here is the number of hours’ sleep you should aim for each night, according to the science from multiple medical fields.

Age in Years	Recommended amount of Sleep
0-1	14-15 hours
1-3	12-14 hours
3-6	10-12 hours
7-12	10-11 hours
12-25	8-9 hours
26-64	7-9 hours
65+	7-8 hours

We’ve just been looking at how important sleep is for our brain and body.

In spite of this, quite a few people skimp on sleep hours and try to get by with the least number possible. Studies suggest that many adults “survive” on less than six hours’ sleep per night, possibly less if they have electronic devices in the bedroom that go off and interrupt their sleep cycle.

Sometimes this may be due to misinformation about sleep. More often than not, the students I talked about in my introduction believed they slept as much as they needed to: sometimes as little as four hours. The reality is that four hours are not nearly enough for an excellent sleep. Sleeping so little on a regular basis will in fact impair not just their immediate performance but also their longer-term health and wellbeing.

Book author Stan Rodski.

Excellent sleep is about not only the quantity of sleep but also the quality. It’s not just that many people aren’t getting enough sleep, it’s also that their sleep is often punctuated by wakefulness. Over time, lack of quality sleep can lead to chronic health problems, or cause chronic problems to worsen.

This is an edited extract from The Neuroscience of Excellent Sleep by Dr Stan Rodski, Harper Collins, out now, $35.

Originally published as Sleep expert reveals exact amount of sleep you need at your age