Chapter 19
A Good Night’s Sleep — Part 2
Doing vigorous exercise, like fast walking, late at night alerts the sympathetic system and releases stimulating hormones and neurotransmitters that make it harder for our minds and bodies to switch to deep sleep mode. So it’s best to take exercise earlier in the day rather than before bedtime. Some people find that eating a late evening meal leads to a troubled night’s sleep, while others find it helps. So it’s best to work out which suits you. Certainly the content of food and drink before sleep matters, and the ability to tolerate late eating declines as we get older. Aged cheese, bolognaise sauce, bacon and other cured meats, including sausage, pastrami, corned beef and ham, contain hefty doses of tyramine, an amino acid that triggers brain alertness. Some Italian wines and several beers also have a high tyramine content. Tyramine stimulates the production of noradrenaline, a neurotransmitter that is part of the sympathetic nervous system’s fight-or-flight response, meaning that we feel alert and awake – ready to fight or flee! Chocolate and coffee contain caffeine, which is also a stimulant. High carbohydrate meals can disturb sleep, as can acidic foods and spicy foods. Foods that are high in fibre, such as broccoli, cauliflower and carrots, can be challenging for digestion at night and are best taken earlier in the day. The traditional ‘night cap’ is also problematic because, although we will get to sleep more quickly after alcohol, sleep cycles and length of both NREM and REM are disturbed. As the alcohol is metabolised, awakenings become more frequent, which is why alcohol disrupts sleep. The response to these stimuli is genetically programmed – in other words, some people have no problem taking tyramine-or caffeine-rich foods at night. Later on, I will discuss foods that help NREM sleep.
Chapter 5: A Good Night’s Sleep
There has been an explosion of research into new technologies to promote NREM sleep. Using sound stimulation, such as listening to pink or white noise, can enhance deep sleep and lead to better memory function the next day. White noise contains all of the frequencies audible to the human ear. Pink noise is white noise with fewer higher frequencies. It increases the intensity and slows down the speed of NREM waves, thus allowing more time to clear toxins, improving the retention of learning and memory and reducing anxiety. It doesn’t work for everyone but some report good results with it.
Other promising and exciting new technologies have not been fully validated although some are commercially available. A popular new technology is a band worn around the head with sensors to detect and track slow brain waves. A stimulus is applied by the band to the slow waves, which causes them to lengthen and slow even more, all of which may deepen NREM sleep.
Chapter 5: A Good Night’s Sleep
The optimum sleep period for adults irrespective of age is seven to nine hours. Our TILDA research has shown that getting less than seven and more than nine hours of sleep after the age of 50 are both linked to future problems with mental abilities, such as memory, concentration and learning. During slow wave sleep (NREM), the spaces between brain cells fill with additional fluid, called the cerebrospinal fluid, which bathes the brain and the spine. This washes away toxins that have accumulated during the day, including those implicated in dementia – beta amyloid and tau protein. It is important that these toxins and waste products are regularly cleared by the cerebrospinal fluid otherwise they will accumulate and block transmission of signals between brain cells. One very elegant experiment showed that missing sleep for even one night was associated with higher tau levels compared with those after one good night’s sleep in healthy middle-aged men. Given that missing one night of sleep results in an increase in the level of tau, it is likely that over time, repeated sleep disruption will have long-term detrimental effects on the brain and mental abilities. Therefore, insomnia in mid-life should be treated with the same gravity as high blood pressure and diabetes – all of which are risks for poor brain health in later life. As young medical students, we took advantage of every opportunity to attend the different faculty balls each year. It didn’t matter which discipline held the ball – a ball was a ball. So we went to the Arts Ball, the Ag Ball (Agriculture), the Commerce Ball, the Law Ball and, of course, the Med Ball. The one beauty tip at the time that I clearly recall, which was a mantra among the dedicated female ‘ballers’, was to be sure to get a good night’s sleep before the ball so that your skin looked fresh without dark rings around the eyes – our ‘beauty sleep’.
Chapter 5: A Good Night’s Sleep
We now have a biological explanation for this axiom. Researchers from the University of Manchester have discovered that ‘looking as fresh as a daisy’ after a good night’s sleep has fundamental biological roots. Collagen is one of the most abundant proteins in the body, responsible for a third of our body architecture. We can think of collagen as the body’s scaffolding. It supports the skin, tendons, bones and cartilage. Collagen provides the body with structure, ensuring integrity, elasticity and strength. It is closely aligned with sleep and with age. There are two types of collagen – a thick fixed type and a very thin ‘sacrificial’ collagen. A good analogy for the two types of collagen are the bricks in the walls of a room which are the permanent part (thick, fixed type), and the paint on the walls, which are the non permanent part (thin collagen fibrils). The collagen fibrils need to be replenished regularly because during the day, this thin collagen takes the brunt of wear and tear and is replenished during sleep. This process is governed by genes but may not work as efficiently as we get older. We look so much better after a good night’s sleep because we have replenished the sacrificial collagen necessary for skin integrity, including around the eyes where skin is thin and dark rims easily form. How often have you been asked by your doctor if you snore? Hardly ever? Or even never? Yet snoring can be an early sign of underlying health problems. Clearly, if you have a partner, you will be made aware of your own regular snoring. If you sleep alone then waking with a dry mouth may be a clue. Heavy snoring is linked to a disorder called sleep apnoea, characterised by pauses in breathing during sleep. If the pauses last for ten seconds (long enough for one or more breaths to be missed) and occur repeatedly, then oxygen levels drop. The reduction of oxygen to the heart can lead to heart attacks, strokes and decline in memory and concentration. When oxygen drops, stress hormones surge. Those hormones contribute to high blood pressure, which most people with sleep apnoea experience. Sleep apnoea is present in 3 per cent of 20–44-year-olds, 11 per cent of 45–64-year-olds, rising to 20 per cent of people over 60. It is diagnosed by an overnight sleep test called a polysomnogram, where wires on the head and chest track brain waves as well as heart and breathing patterns.
Chapter 5: A Good Night’s Sleep
Anyone who snores loudly, wakes without feeling rested or has high blood pressure, diabetes or is overweight is more prone to sleep apnoea. It is important that this is addressed as the risk of adverse health consequences declines dramatically with treatment. A very effective treatment, one that helps 90 per cent of those who adhere regularly to the method, is use of a face mask that prevents obstruction at the back of the throat by changing the pressure in the mouth and throat. The mask system is referred to as a continuous positive airway pressure (CPAP) device. Simple snoring that is not very loud and without any other symptoms can usually be handled by turning on one’s side. Sleep matters when it comes to our susceptibility to infection and to fighting infections when we do get them. During sleep, the immune system releases proteins called cytokines, whose main role is to target infections. Some cytokines also help to promote sleep. Sleep deprivation reduces both the production and the release of protective cytokines, causing a double whammy if you skimp on shut-eye.