Introduction to Sleep
What is sleep?
Sleep is characterised by reduced levels of consciousness and alterations in neural activity which promote physical and mental repair. Sleep occurs in stages and there are two major divisions of our sleep state. These are known as rapid eye movement (REM) and non-rapid eye movement (Non-REM). Non-REM is further divided into four different stages. These stages occupy approximately 80% of sleep, with the theta and delta stages often referred to as “deep sleep”. REM occupies approximately 20% of sleep and occurs in 90 minute cycles. Non-REM is characterised by reduced brain activity or ‘rest’ whilst REM sleep is characterised by heightened neural activity.
Nerve-signalling chemicals called neurotransmitters largely control the sleep-wake cycle by acting on different groups of nerve cells in the brain. Neurotransmitters such as serotonin and norepinephrine are released to keep the brain active whilst we are awake, whilst melatonin increases as light levels fall to promote sleep. Sleep also helps to clear adenosine from the brain which builds up during the day and contributes to increases in sleep urge and reductions in cellular metabolism. The sleep-wake cycle is also regulated by other factors such as eating and exercise routines and therefore keeping these in check will help to maintain good sleep.
How much sleep is enough?
The amount of sleep an individual requires depends on a number of factors, including age. Infants require approximately 16 hours a day and teenagers require approximately 9 hours. For most adults, research indicates 7 to 9 hours per day is optimum; however women in the first 3 months of pregnancy often require more than usual.
The amount of sleep required is individualised, however ensuring we get enough is vital. Up to 45% of the world's population doesn't get enough sleep. The widespread practice of “burning the candle at both ends” in modern times has created a state of sleep deprivation in many that is considered the norm, but in reality, may be harming our health and reducing our ability to function optimally on a daily basis.
Risks of Sleep deprivation
Effects of sleep deprivation
Research shows that sleep loss (less than 7 hours per night) may have wide-ranging effects on health by increasing the risk of; obesity, diabetes, cardiovascular disease, hypertension, depressive moods and performance.
Obesity: 61.9% of the UK population is currently classified as overweight or obese. A lack of sleep can contribute to this as it can lower levels of leptin, a hormone produced that suppresses appetite, and increase levels of ghrelin, a hormone that stimulates appetite. Thus, a lack of sleep may result in greater cravings for calorie-dense foods and increase portion sizes. Often when we are tired we opt for high-sugar, calorie dense foods such as chocolate, sweets or biscuits to provide us with an energy boost. These types of foods are a ‘quick fix’ which impair blood glucose levels and further reduce energy levels, resulting in a negative cycle. Research indicated a U shaped relationship between BMI and sleep whereby too little or too much sleep can be detrimental to weight.
Diabetes: Sleep deprivation can lead to increases in cortisol in an attempt to stay awake, which increases glucose release into the bloodstream and thus impairs blood sugar balance. Chronic impairments in blood sugar have been shown to lead to insulin resistance – a precursor for type 2 diabetes. Adults who reported 5 hours of sleep or less were 2.5 times more likely to have diabetes in old age.
Cardiovascular disease and Hypertension: Reduced sleep has been linked with increased activation of the fight or flight system which increases blood pressure, heart rate and reduces the ability to digest food. This, alongside factors such as being glucose intolerance and overweight, increase the risk of cardiovascular diseases such as heart attacks and strokes.
Cognitive Performance: Sleep is required to enable us to think clearly, react quickly and create memories. Studies show that sleep deprivation directly affects one’s ability to make clear decisions and multi-task. This can result in lower cognitive performance, reduced work productivity and increased stress.
Mood: Studies have shown individuals limited to only 4.5 hours of sleep a night for 1 week reported feeling more stressed, angry, sad and mentally exhausted. Upon resuming normal sleep their moods dramatically improved.
Jet-lag: Jet-lag type is a temporary circadian rhythm sleep disorder that occurs when there is a transitory mismatch between the timing of the sleep-wake cycle caused by a change in time zone. Individuals may experience disturbed sleep, decreased subjective alertness, general malaise and somatic symptoms such as gastrointestinal disturbance.
Minimize this by adjusting mealtimes and sleep patterns closer to the schedule of your destination prior to leaving. In addition, maintaining good hydration during your flight by drinking water can reduce the effects of jet lag.
Interventions
Good Sleep Hygiene
Sleep hygiene is a variety of different practices that are necessary to have quality night-time sleep and full daytime alertness. The following tip sheet demonstrates some areas to focus on and to avoid to aid with good sleep hygiene.
Kommentare