Matthew Walker, Professor of Neuroscience, University of California, Berkeley
Picture this scene. You roll out of bed, wash, and throw on some clothes, before heading out of the house. Still not fully awake, you buy a coffee as you head towards work. A few minutes later a jolt of caffeine reaches your brain, and you finally feel somewhat human again. Caffeine is not a health supplement. It is the most widely abused psychoactive stimulant on earth. Ingesting ever stronger, ever more frequent shots of caffeine is now the longest and largest unsupervised drug trial ever performed on the human race.
When caffeine enters the body it has some profound health effects. Some good. Some not so good. As it winds its way up to the brain it battles with a neuro-chemical called adenosine, elbowing it aside, then latching on to adenosine receptors in the brain. Once caffeine is settled in these brain receptors, adenosine is blocked, preventing the feeling of sleepiness. Caffeine is now inducing wakefulness, as opposed to adenosine slowly promoting sleep. The problem is that most people do not realise how long it takes to overcome a single coffee. Caffeine typically has a half-life in the human body of about seven hours, although genetic variations can speed up or slow down this process. Fourteen hours after you’ve had your morning cup of coffee there will still be some caffeine sniffing around those adenosine receptors. Put this together with a trend towards either larger, stronger, or more frequent amounts of coffee, plus the long half-life of caffeine, and that single cup of morning coffee suddenly injects enough caffeine into the body and brain for hours, all the time suppressing the neuro-chemical adenosine.
When adenosine is blocked something called sleep pressure is suppressed. Adenosine should be allowed to rise throughout the day. It should rise every single minute, peaking after twelve to sixteen hours. Once sleep pressure rises beyond a certain point the wake regions of the brain begin to shut down, then, a few hours after sunset, we should be ready to fall asleep. But we don’t, and it’s having profound health consequences.
One hundred years ago most people slept around nine hours per night. At that time, less than two percent of people slept six hours or less. By the mid twentieth century, the amount of sleep people got began to decline. Now, thirty percent of people have less than six hours sleep. Sixty-five percent of people have less than the minimum recommended account of seven hours a night sleep. This has huge health consequences, leading the World Health Organisation to label it a ‘global health epidemic’. A lack of sleep is now directly linked to developing Alzheimer’s disease. For those not worried about a distant disease sometime in the future know that being sleep deprived makes you less creative, less productive, less able to memorise, and a poorer worker, who is more likely to take the easy way out when undertaking tasks. Intelligence, motivation, effort, efficiency and effectiveness all take a nose dive in people who sleep less than seven hours. Yet, we live in a culture that overvalues people who undervalue sleep. Claiming four, five, or six hours sleep has become proud boast that makes people who have eight hours of sleep seem lazy. In reality, this is utter foolishness. A lack of sleep promotes cancer and diabetes while reducing longevity. It makes people emotionally unstable, while worsening the symptoms of poor mental health. Many people in this room will know someone who has had a heart attack, a stroke, or a heart operation. A lack of sleep promotes cardiovascular disease, even if it isn’t the only cause. But it is in childhood that sleep first benefits our health, and, as many people here today are newly minted parents, making sure your children sleep well is our first point of concern.
There are two types of sleep. The first type is called non-REM sleep. During this phase there is an epic display of neural collaboration and self-organisation in the brain. Brain cells unite together as one, then sing together in harmony. There is a unified chant, then a pause, that repeatedly ripples across the whole brain. This unified ripple knits together all the regions of the brain, opening up communication possibilities between distant brain regions. It acts as a mode of transportation, transferring memories and emotions, while removing unnecessary neural connections. All of this is caused by non-REM sleep.
As the night deepens, another type of sleep called REM sleep starts to dominate. It happens at the beginning of the night too, but truly benefits human health as the night progresses. During this time there is an extraordinary change in the cocktail of brain chemicals. The stress chemical nor-adrenaline shuts down. Stress and anxiety decrease. Emotional wounds are healed. REM sleep allows people to ditch bad emotional memories, and gives scientific credence to the age-old advice of ‘you’ll feel better in the morning’. This why it’s so important not to get tempted into argument, finger wagging, making big decisions, or firing off an angry text or email in the evening. By morning time you will different, you will react differently, in a more dignified fashion, and the anger and emotion will have dispersed.
During REM sleep the brain moves into a creative phase. It builds connections between seemingly unrelated pieces of information, while creating abstract knowledge, and super concepts out of the large stores of knowledge we accumulate. While non-REM sleep joins together the distant areas of the brain, REM sleep pulls together all the memories and information. During this time of sleep the brain is alert, it’s not in a semi-dormant state, and some people are thirty percent more alert during REM sleep than when they are awake.
REM sleep is dominant in infants and unborn children. When a mother has just one glass of wine the breathing rate of her unborn child drops from 381 beats per hour to just four beats. At the same time, REM sleep ceases in the child. If she continues to drink alcohol while breastfeeding, REM sleep in her baby diminishes by thirty percent.
When infant REM sleep is reduced it has monumental effects upon their linguistic and social development. It curtails their learning and absorption of languages. In contrast, infants who sleep well can deduce high level grammatical structures from new languages, all facilitated by REM sleep. Memory is aided and new skills are learned during this phase of sleep. This is why it is crucial for babies and young children to develop good sleeping patterns early in life. From the age of three-to-four months, babies can be got into a daily rhythm of sleep during the day and the night. From the age of one, key biological rhythms are kicking in that start to force the young child into routine, enabling them to get to bed at a set time, while going longer periods without waking. The key to this is putting babies to bed, during the day or night, when they are sleepy rather than when they are actually asleep. Putting the child to bed when they are merely drowsy helps them to self-soothe, teaching them the ability to put themselves to sleep, and enabling good sleeping habits throughout childhood and later life. Children who sleep longer are more intelligent, better memorisers, and better socially.
Teenagers need sleep too — lots of it. Perhaps as much as twelve hours a day, but not less than nine. Their body needs it to grow their brain and body. Stop them from sleeping and you are doing a genetic engineering experiment on them, that will impact everything from their weight to their grades to their emotions to their physical growth. They aren’t being lazy when they refuse to get out of bed.
Children are not the only people who need sleep to develop a healthy emotional life. In adults, a part of the brain called the amygdala is severely affected by sleep deprivation — and by deprivation we mean anything less than seven hours a night. This part of the brain is responsible for anger and rage. It becomes sixty percent more active in the sleep deprived, causing them to lash out at people with uncontrolled reactivity, as their emotional states swing up and down. The striatum is the region associated with pleasure and reward. This then becomes hyperactive leading to hedonic, pleasure seeking behaviour. This may lead to risk-taking, addiction, or even immorality.
Beyond the emotional and intellectual life of the brain the physical brain is very much harmed by a lack of sleep. Fully sixty percent of Alzheimer’s disease patients have at least one sleep disorder, which disrupt the transmission of memories from one part of the brain to another. This is partly why people with Alzheimer’s disease hold on to old memories but cannot form new memories: they simply cannot transmit them across the brain during the night-time due to lack of sleep.
Depriving yourself of sleep is a significant risk factor for Alzheimer’s disease. Just a few years ago, a whole new biological system was discovered in the human body. This is the glymphatic system. Within the brain there are glial cells that sit next to neurons. During sleep, these glial cells shrink by sixty percent, which enlarges the space around the neurons. Cerebral spinal fluid flows into and through this newly formed space, cleaning out junk proteins and plaques that accumulate during the day. It bathes the brain. It then drains this junk down through the body, into the liver and kidneys, where it is filtered, then expelled from the body. This remarkable process happens during sleep. When all is working properly the junk is cleared from the brain, preventing the build-up of amyloid and tau that is symptomatic of Alzheimer’s disease. Conversely, having insufficient sleep over the course of decades means that the glymphatic system has not done its job of cleaning the brain, hugely increasing the risk of Alzheimer’s disease.
The body is very much effected by a lack of sleep. Two scourges of our time are cardiovascular disease and diabetes. Every single year there is an experiment on the hearts of 1.5 billion people. This experiment happens in the month of March, when daylight saving time begins, and the clocks go forward. That night, almost everyone loses one hour sleep. The next day, there is a spike in heart attacks. The reverse is also true: when we gain an hour’s sleep in October, there is a dip in heart attacks. Of course, this risk is worsened by the diets we eat and the exercise we fail to do. Nevertheless, it shows the power of just a solitary lost hour of sleep on human health.
This spike in heart attacks is backed up by other data from around the world. A large study of half a million people found that sleep deprivation led to a 45% increased risk for cardiovascular disease. Having six hours or less on a regular basis increases the risk of a heart attack by 400%. While regularly having between 5-6 hours sleep leads to a 300% increased risk of hardening of the arteries. This is worsened by a parallel reduction in human growth hormone, which otherwise would heal the body, and, under normal circumstances, heal the inner lining of damaged blood vessels.
Diabetes often goes hand in hand with cardiovascular disease. There is a strong association between diabetes and sleep deprivation. This hypothesis has been tested in sleep laboratories, where a lack of sleep induces pre-diabetes in a very short time. The cells of our body become less receptive to insulin, that washes away the sugar we eat, leading to rising blood sugar, insulin resistance, and eventually diabetes.
Now imagine that we had a gene editing tool that altered the very DNA that makes up your body. An editing tool so powerful that it could edit, then change, how over 700 genes work. Such an editing tool exists, and has always existed. It is sleep. Less than six hours of sleep distorts the expression of 711 genes. Some are revved up. Some are slowed down. Gene expression involved in inflammation and cardiovascular disease is increased. At the same time, gene expression involved in optimal immune response, weight, and cholesterol, is reduced, meaning that the immune system and the heart is further compromised. All done by a lack of sleep.
As the immune system is compromised, natural killer cells that target tumours, preventing them from developing, are reduced. Just one night of four hours’ sleep obliterates natural killer cells by seventy percent. Go without enough sleep on a consistent basis and the immune system remains in chronic, compromised state, increasing the risk of cancer. This risk is so great, and the evidence so convincing, that the Danish government has started paying compensation to women who worked the night shift in government jobs, then developed breast cancer. Working the night shift raises the risk of cancer to such a degree that the World Health Organisation has labelled night work as carcinogenic.
Yet sleep is obviously not the only challenge to human health. We eat food awash in inflammatory omega-6 vegetable and seed oils, which are possibly the most damaging food known to Man. A single hot meal of food cooked in vegetable oil, or foods containing vegetable oils, leads to a hardening of the arteries that lasts for twenty-four hours. At the end of this short time period, your arteries temporarily resemble those of an eighty year old. Even a cigarette only damages arterial lining for four hours. These oils then store in body fat for up to two years, triggering inflammation, which in turn triggers heart disease and cancer, while also impacting upon our hormones. They put the brain in a vice-like grip, reducing memory, creativity, and cognitive function. These oils are everywhere. In chips. In curry. In samosas. In burgers and kebabs. In bread. In croissants and cakes. They are the scourge of our time. If you only make one health change this Suhba it should to make a firm intention never to have vegetable or seed oils again. You can easily find or make delicious feasting food without it. Add together a poor diet, with a lack of exercise, a higher ethnic or genetic risk for cardiovascular disease, then throw in a persistent lack of sleep, and you are throwing away your life.
Throughout history there have been correctives to various populations. These correctives have included war, famine, viruses, and infections. One of the most devastating pandemics was the Black Death in the fourteenth century that killed two hundred million people. The plague haunted the European and Muslim world well into the nineteenth century killing millions of people. When European diseases travelled across the Atlantic to the New World with the slave trader Christopher Columbus and other colonial European nations, new diseases spread through Native American tribes, killing up to one hundred million of them. In 1918, Spanish flu infected 500 million people, killing another one hundred million people.
The virus of our own time may well take a different form. As we have often mentioned, many people are infected with the virus of internet addiction, smart-phone addiction, messaging addiction, or simple overuse of electronics. When the iPad is used in the evening, people lose significant amounts of REM sleep, damaging their intellectual creativity. Even one evening of iPad use leads to a reduction of the sleep hormone melatonin, which then stays persistently low for several days afterwards. This makes it more difficult to get to sleep, along with less sleep. It is problematic to use computers and phones in the evening even for a few days a week, as melatonin remains constantly suppressed. This effect is worsened in infants and children. Backlit screens used after sunset causes sleep deprivation. As we have just heard, sleep deprivation induces all manner of diseases. Our devices may well be contributing to our physical and cognitive decline, and early death, by reducing the amount of sleep we have.
This fast-paced, dopamine inciting, information saturated world, pinging us with messages and updates from across the globe never stops. Our brain never gets a rest. The only time we do get a rest from it all is when we finally put them down and our head hits the pillow at night. But here’s the thing: only resting from information overload, messages, calls, and the screen just before sleeping is perhaps the worst thing you can do. When we stop and slow down only at this time it leads to rumination and reflection. The brain finally has time to think for itself away from interruption. This leads to a form of psychological distress that causes insomnia, altered patterns of brain activity, while promoting hormones that raise adrenaline and cortisol. There needs to be a switching off from overactive thought several hours before bedtime. In addition, several times throughout the day there needs to be a period of switching off, deep thought, and reflection, such that the brain gets to rest at times other than when our head hits the pillow at night. The perfect time for this is after each obligatory prayer. A short period of time of dhikr, of reflection, or of gratitude is perfect for resting the brain and helping to sleep at night.
The traditional Muslims of Damascus really knew what they were doing when it came to bio-chronological health. They did their memory work early in the morning, which we now know is the very best time for memorisation. At the other end of the day, the habit of older Damascenes was to excuse themselves from guests and duties at 10.00 pm to go to sleep. They did this in with their innate Damascene manners: with politeness, with the offer of leaving food and drink for any guests, but to bed they went, without fail. This is probably the ideal time to repair to bed. It is not the ideal time to hit up a late night fried chicken or kebab shop, nor to remain on the screen getting your electronic dopamine fix.
Beyond a fixed, earlier bedtime, beyond getting off the screen in the evening, there are a number of things a person can do to help deepen their sleep. It starts in the morning, by restricting your caffeine intake to this time, and having only one coffee or none at all. In fact, once your body gets used to not having caffeine, the small amount of caffeine in decaffeinated coffee is enough to induce alertness, without jeopardising your sleep or health. At some point during daylight hours there needs to be that thing many of you dislike. Namely, exercise. It helps with sleep. Then, throughout the day, periods of quiet reflection and gratitude, away from distraction. After Maghrib, screen time needs to be slowly reduced, until, by Isha, devices are put to bed until the next day. Then, when you put the lights on in your house during the evening, they should be warm yellow lights, not operating on the blue light frequency. They should be up-lighters or lamps, rather than ceiling lights, as ceiling lights have the effect of mimicking the sun shining down upon on, keeping us awake. As Isha enters, the temperature of house needs to be lowered. Anyone married to a Pakistani wife knows the battle for control of the heating thermostat. But lowered it must be. The ideal temperature of a house after Isha is 18 degrees Celsius. Then, once daylight has completely faded, favour and close blackout curtains. Socialising with friends and family should stop by 10:00 pm, as should work. People will soon get used to your strange habits. There will be times when this is not possible, but make it a general rule. Then, aim for between seven and nine hours sleep per night. Less than seven hours and you really are damaging your brain, heart, hormones, immune system, and reducing your life, especially if this is combined with the evil that is vegetable oil.