Sleep - is this your missing ingredient to a long and healthy life?
In today’s fast-moving world, there is a tendency to feel that we have not achieved, seen or interacted enough. In this over-stimulating environment, something has to give, and for many, the sacrifice is both the quantity and the quality of our sleep. On average we sleep 1.5 hours less than we did a century ago (summarised in 1). Research into the health effects of sleep deprivation over the last decade or so has revealed the devastating impact of a sleep deficit. It seems that sleep deprivation can affect not only our mood and ability to concentrate, but contributes to a range of serious health problems. We know that diet and exercise are crucial to health, but it seems that sleep quality and quantity is at least as important. Here is what we discovered.
Sleep deprivation upsets our hormones
Sleep deprivation has been shown to alter both metabolic and endocrine function, affecting the secretion of growth hormone and cortisol, and the metabolism of glucose by insulin. In addition, the secretion of leptin and ghrelin, hormones that regulate our appetite, is disturbed following sleep deprivation, resulting in increased food intake and weight gain. Overall, chronic sleep deprivation has been linked to a higher risk of both weight gain and developing type II diabetes. (Summarised in 2).
Sleep deprivation causes inflammation, affects cardiovascular health and damages our DNA.
Lack of sleep increases the activity of our sympathetic nervous system, increases blood pressure, and kick-starts inflammation. These three effects probably combine to bring about the higher risk of developing cardiovascular disease that is seen with sleep deprivation. (Summarised in 1 and 3). Some studies show that sleep deprivation also damages our DNA, either by increased oxidation of DNA or reduced ability to repair it, and this damage could increase the risk of cancer (4).
Sleep deprivation damages the brain
We all know our brains don’t function well after a bad night’s sleep. It has long been known that sleep deprivation reduces our cognitive function - our reasoning, memory, attention and language abilities. It also affects our mood, making us more irritable and more depressed (5). A recent study showed that sleep loss activates immune cells within the brain itself, causing them to ingest more synapses in the brain, possibly because the synapses are worn out from over-use. The increased activation of one of these cell types, the microglial cell, is thought to make the brain more susceptible to other types of damage (6).
Now it has been shown that beta-amyloid, the toxic protein that accumulates in the brain in Alzheimer’s disease, is normally cleared from the brain during a phase of sleep known as deep non-REM (rapid eye movement) sleep. When deep non-REM sleep is blocked, beta-amyloid protein builds up in the brain. Chronic lack of non-REM sleep therefore can cause sufficient beta-amyloid build up to cause Alzheimer’s disease (7).
If that wasn’t enough, mortality from all causes increases with chronic sleep deprivation by around 10% (summarised in 3).
How to improve your quality of sleep
Achieving sufficient, good quality sleep is clearly crucial to our health, but for some, a good night’s sleep is elusive. Here are some things you can do to help:
Optimise melatonin secretion
Melatonin is secreted into our brains at night to help promote sleepiness. Because of our use of artificial light which can delay our production of melatonin, we go to bed later than ever, and may have trouble sleeping when we do go to bed. In particular, screens and energy-efficient light bulbs (fluorescent and LED lights) are a problem, because they emit blue light, and blue light suppresses melatonin production more than any other wavelength of light (8).
We can improve our production of melatonin by exposing our eyes to unfiltered daylight, preferably in the morning, for 30-60 minutes a day. In the evenings we should aim to minimise our exposure to artificial light, particularly blue light, aiming to avoid looking at screens for at least an hour, preferably longer, before we plan to go to bed. While asleep we should aim for complete darkness, but if we need night lights for nocturnal wanderings, we should use dim red lights so that melatonin production is not turned off, and we can get back to sleep.
At certain times in our lives we can be overwhelmed by feelings of anxiety and other emotionally distressing states that keep us awake at night. There are a number of ways to deal with these emotions so that they don’t interrupt our sleep. Writing down feelings, talking them through with a trained professional or a trusted friend, performing breathing meditation, playing calming music, and getting enough exercise during the day are just some methods of dealing with these thoughts.
Exercise, food and drugs
Taking regular exercise helps reduce levels of anxiety, improves the quality of our sleep, and reduces the amount of time it takes to get to sleep. Caffeine, nicotine and alcohol taken within a few hours of sleep can stimulate and increase anxiety and reduce the quality of sleep.
There is some evidence that foods high in tryptophan, an amino acid that is used to make the neurotransmitter serotonin, can help us feel sleepy. This is particularly so when consumed with carbohydrates, which help with uptake of tryptophan into the brain. Tryptophan is found in high protein foods like nuts, soy, dairy, fish and meat. Certain foods like tart cherries or cherry juice are thought to help boost levels of melatonin, and have been found to improve length of sleep in some studies.
Keep it cool
Many people over-heat their bedroom. We sleep better when the temperature is between 15-20 degrees Celsius.
Sticking to a bed-time routine like going to bed at around the same time each night, and creating a night time routine for getting ready for bed helps prime our bodies for sleep. Bon nuit!
Nagai, M. et al (2010) Sleep Duration as a Risk Factor for Cardiovascular Disease- a Review of the Recent Literature Curr Cardiol Rev. 6: 54–61.
Sharma, S. and Kavuru, M. (2010) Sleep and Metabolism: An Overview Int J Endocrinol. Published online 2010 Aug 2.
Mullington, J.M. et al (2010) Sleep Loss and Inflammation Best Pract Res Clin Endocrinol Metab. 24: 775–784.
Everson, C.A. et al (2014) Cell Injury and Repair Resulting from Sleep Loss and Sleep Recovery in Laboratory Rats Sleep. 37: 1929–1940.
Lo, J.C. (2016) Cognitive Performance, Sleepiness, and Mood in Partially Sleep Deprived Adolescents: The Need for Sleep Study Sleep 39: 687–698.
Bellesi, M. et al (2017) Sleep Loss Promotes Astrocytic Phagocytosis and Microglial Activation in Mouse Cerebral Cortex Journal of Neuroscience 37: 5263-5273
Mander, B.A. et al (2015) β-amyloid disrupts human NREM slow waves and related hippocampus-dependent memory consolidation Nature Neuroscience 18:1051–1057 (2015)
Harvard Health Letter Blue light has a dark side: Exposure to blue light at night, emitted by electronics and energy-efficient lightbulbs, can be harmful to your health. Updated: September 2, 2015Published: May, 2012