By Patrick Holford
Sleep.
Sleep is how the brain recovers. There is now overwhelming evidence that sleep is a ‘brain essential’ and just like Goldilocks, it seems we need just the right amount. Getting too much, or too little, increases our risk for cognitive decline.
If you want to put a number on it, it appears the optimal amount of sleep for brain health is seven hours in total. And, for the light sleepers among us, there is some debate about whether it needs to all be in one go – one study found that a nap after physical exercise was in fact good for the brain, reducing the risk of cognitive impairment.
However, for those of us with problems sleeping, or who get consistently less than the recommended seven hours, we may be literally doubling our risk of age-related cognitive decline. A UK study of Whitehall civil servants, started in the 1980’s, examining their health from the age of 35 and onwards found that ‘persistent short sleep duration at age 50, 60, and 70 compared to persistent normal sleep duration was also associated with a 30% increased dementia risk’. But it’s not just future risk of dementia that lack of sleep cranks up: it’s our ability to function the next day and to feel good. Lack of sleep decreases empathy and increases negative emotions.
Sleep can be thought of as the brain’s housekeeper. During sleep, blood and cerebrospinal fluid circulation improves, and waste products of brain metabolism get removed. These waste products include both oxidants and amyloid protein, associated with Alzheimer’s and brain inflammation, which starts to accumulate after just one night of sleep deprivation. That’s a big reason your brain needs this downtime.
One of the key powerhouses that helps clean up our brains while we sleep is melatonin. So why doesn’t melatonin do this all the time? As nightfall approaches, our brains convert serotonin into melatonin. Deep in the centre of our brain – the centre of our soul according to the philosopher Descartes, or the ‘third eye’ chakra in Yoga – melatonin is made in the pineal gland. Sensitive to light, most likely through receptors at the back of our eyes, the pineal is the only endocrine gland in contact with the outside world. Darkness stimulates the production of melatonin, whereas exposure to light (cue that late night phone scrolling!) suppresses production.
Melatonin, then, keeps us ‘in sync’ with the day/night cycle. (Indeed, some frequent flyers find that taking melatonin supplements can help them adjust more quickly to a new time zone and avoid the tired-all-day feeling of jet lag and give them a better night’s sleep.)
Increasing levels of melatonin help us fall asleep and keep us asleep, so what is melatonin actually doing?
Although there are many by-products of the day’s brain activity, one big slice of the toxins that accumulate in the brain are various oxidants. Apart from all the antioxidants and polyphenols we can eat to keep our brains young, melatonin is perhaps the most important antioxidant helping to disarm these oxidants and restore the mitochondrial energy factories to full function.
Melatonin is made from a type of tryptophan, 5-HTP, a potent antidepressant. Melatonin is also a powerful anti-inflammatory and supplementation has been used to speed up recovery from cancer, covid and cardiovascular disease.
Melatonin, then, is crucial for brain health and sleep routine, and a loss of this natural circadian rhythm, and lower brain levels of melatonin are found in those with cognitive decline.
But there’s something else going on while we sleep, and particularly as we dream, that supports brain health.
All being well, after about 30 minutes, we enter a period of deep sleep when our heart rate reduces, our blood pressure drops and our breathing becomes slower. This is the most restorative stage of sleep when tissue repair and regeneration occurs. After around 90 minutes, we then shift to a period of REM (rapid-eye-movement) sleep, which is when most dreaming occurs. As far as the brain is concerned, the most critical phases of sleep are these bursts of REM sleep. Lasting about 30 minutes, we move back and forth between deep sleep, lighter sleep and REM,on average between three to five times a night, with the REM stage ideally accounting for around 25% of our overall sleep time.
During the night, and especially during the deep and REM sleep phases, our brains also produce higher levels of growth hormone. This hormone helps with the repair and regeneration of our body’s tissues while melatonin helps clear out the waste products of metabolism.
However, when we are stressed, high levels of the stress hormone cortisol suppress REM sleep and growth hormone production, diverting energy away from repair, and effectively speeding up the brain’s ageing process. In fact, people who are deprived of REM sleep won’t feel fully rested on waking and in turn are more likely to get depressed. When they do get a chance to sleep, they will often have longer periods of REM sleep, of which suggests that our brains need this time while we’re asleep to process what’s been happening in our lives. One theory is that negative emotions such as anger, fear, sadness, or frustration, often suppressed in our hectic lifestyles or the modern workplace, can be experienced and released during dreaming. To test this theory, when we have a strong negative emotion in a dream, it’s useful to track back to our experiences the day before when we felt a similar emotion.
A good night’s sleep might help us process a bad day at the office, major stress, or prolonged anxiety, stress or overwhelm, age the brain and increase our risk of cognitive decline and dementia in the future. This has been shown by tracking people who have had two or more major stressful events such as death of a spouse, child or grandchild, divorce, financial or health problems, but also perceived psychological stress in adulthood and levels of neuroticism.
Stress is also linked to our perception of control in our lives. One study assessed people’s work based on two criteria: how demanding the job was and how much control the person had. Those who did worse both for depression and cognitive decline had both high demands and low control over the circumstances. For example, a classic example of high stress might be caring for a parent with dementia and dealing with various NHS and social service bureaucracies. Another would be a stressful job where you don’t have the power, or the budget, to make necessary changes. Having too many unfinished things is also a classic source of overwhelm.
But what is stress actually doing to our brain?
The best way to understand this is to talk about the two main stress hormones, Adrenaline and Cortisol, both essential for keeping us safe and alive. Adrenalin is short-acting, kicking in, in under a second and lasting for up to an hour (but usually less). It’s what we needed to get away from the sabre-toothed tiger, or feel ready to take on a sporting challenge or that big presentation. Cortisol, on the other hand, is long acting and its level cycles throughout the day. In the morning, cortisol levels rise to kick start our day and in the evening, as we approach sleep, our cortisol levels should be reducing. But if our cortisol level is high at night we’ll have difficulty getting to sleep and if it’s low in the morning, we’ll be reaching for the caffeine before we’ve opened our eyes.
At an evolutionary level, our ‘stress’ reaction is vital to our survival..
However, when we get stuck in reacting stressfully, sleeping poorly or waking up with stressful thoughts, and operating with a background level of anxiety, we end up with continuous elevated cortisol as a result. This is bad news as excess cortisol is linked by many studies with worsening overall cognitive functioning, memory, slower thinking and poorer social skills, and ultimately, a greater risk of dementia and Alzheimer’s in our later years.
What’s actually going on in the brain is that cortisol triggers these stress responses in the limbic brain which includes the hippocampus. This part of the brain then feeds back to put the brakes on further cortisol release. But, with prolonged stress, or anything else that triggers hippocampal shrinkage, the brakes on cortisol don’t get fully applied so you get into a negative loop of continued cortisol leading to increased hippocampal brain shrinkage.
But this isn’t the only negative feedback chemical keeping us stressed out and stuck. The psychologist and philosopher Oscar Ichazo uses the term ‘doors of compensation’ to describe those things we reach for when we’re stressed, and not all of them are good.
Drinking alcohol, smoking or taking drugs, and sugar are common choices to make us feel better in the short term but the long-term effect is anything but. .
Alcohol, for example, causes an immediate increase in the calming neurotransmitter GABA, which also switches off adrenalin – at least for an hour or so. But there are two main problems with this. Firstly, the effect wears off and drinking too much in the evening actually shuts down GABA receptors the next day, cue the negative cycle of feeling more anxious and more stressed. The second is that alcohol is a neurotoxin and, ultimately, contributes to a brain downgrade, increasing the risk of dementia. It also negatively impacts the quality of our sleep, as the brain ‘shuts down’ rather than getting on with the vital repair and regeneration it needs during those vital hours of shut eye.
Another favourite ‘door of compensation’, especially among those who don’t drink, is sugar.
This is partly because of the ‘feel good’ effect of glucose, stimulating the brain’s reward system but, which in excess, leads us to continue to crave sugar more and more. But what makes the combo of sugar and stress particularly insidious is that glucose cranks up the adrenal system, magnifying the response to stress and corresponding cortisol levels. Just in case you’re wondering, other foods high in protein or fat don’t do this. It is specifically sugar or glucose.
We routinely ‘cope’ with stress by drinking alcohol or eating sugar or both then, the likelihood is that, the next day we’ll feel more dopey and anxious or stressed on waking due to the lack of GABA receptors and lower blood sugar levels. Invariably, we are more inclined to reach for that morning cuppa Joe – a caffeinated drink and something sweet to eat. This then sets you up for more cortisol release, which makes us more stressed so, by the evening, we need more alcohol. This combo increasingly shrinks our hippocampus, the part of the brain which gives the feedback signal to switch off cortisol. Result? We live in a constant state of stress. This is a cycle we need to get out of.
Here are some some simple steps to support your brain and feel better:
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And if you want to get more support and more tools on how to deal with stress and support, then make sure you join us in our next webinar.
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Thank you for reading!
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