This week on the blog we’re deep diving in to the world of sleep cycles. Prior to researching about this my knowledge begun and ended at knowing there were stages of sleep, and one of those stages was REM. I really enjoyed writing this one – I hope you will too! Grab a cup of tea – this is a long one…
Stages of Sleep & Sleep Cycles
Typically there are five stages of sleep, and sleepers (depending on the length of the sleep) will pass through each stage, and revisit stages during the night. A sleep cycle is the progression of the various stages during sleep from Non-REM to REM.
Stage one is the first and lightest stage of Non REM sleep. This stage can be characterized by the presence of slow eye movements, it’s a drowsy sleep stage but the sleeper can be easily disrupted by noise or movements. In this stage your muscle activity is slowing and brain activity begins to slow down. This is also the stage where we can often experience a ‘Hypnic Jerk’ or feeling of falling – sound familiar? While much research has been carried out over the years to figure out exactly why this happens, no concrete evidence has favoured one theory over another. As this occurs to approximately 60% of people, it is most commonly thought of as a result of stress, sleep deprivation, fatigue or caffeine consumption. It’s quite common, and shouldn’t be anything to be concerned about – but important to be aware of why it’s happening, especially if it occurs regularly.
Stage two is where you spend approximately 50% of your sleep cycle. This stage is also the first actual stage of Non-REM sleep. It is harder to wake in this stage as your body prepares for deep sleep. Eye movements and brave waves slow, the body temperature drops, and your heart rate slows down. During this stage you also experience bursts of rapid activity known as sleep spindles, (this next part fascinated us!). Sleep Spindles are bursts of oscillatory brain activity that occur during stage two of sleep. Research has shown that sleep spindles are attributed to sleep quality; the more frequently produced spindles are, the less likely the sleeper is to be woken up, resulting in a better quality of sleep. Sleep Spindles have also been linked to intelligence, as the frequency of spindles seems to indicate how active the brain is, serving as an index of intelligence. If the sleeper has learned something new that day, it is likely that sleep spindles frequency will increase. As children learn a lot of information frequently, sleep spindles are more prevalent in young people attending school. Early studies are also showing a link between abnormal patterns (fast and slow) of spindles and schizophrenia, as well as a lower level of spindles overall compared to the average population.
Stage 3 &4
Stage 3 is known as deep Non-REM sleep. Stages 3 &4 are often paired together, with the American Academy of Sleep combining them in 2007. During these stages you are in a deep sleep, and harder to wake. If the sleeper is woken up during these stages they will usually feel disoriented for a few minutes. During these stages the body repairs itself, regrows tissues (beauty sleep!), and strengthens the immune system. The older you get, the more likely you are to sleep lighter – this has been contributed to ageing, as deep sleep is reduced, as is repairing of the body and regrowth of tissues.
Stage 5 is the final stage of sleep, and is one that we are all most likely the most familiar with. REM (Rapid Eye Movement) sleep is most commonly known as the dreaming stage. You know some nights you feel like you had dream that lasted all night? In reality we dream every 90 minutes and most dreams last anywhere between a few seconds to 45 minutes long! During this stage our eyes our rapidly moving from side to side and brain waves are more active. It is easier to wake sleepers in REM stage, however if woken, the sleeper can often feel groggy, confused and overly sleepy. Once REM stage ends the cycle returns to light sleep again. On average people tend to go through four or five sleep cycles each night – depending on the amount of hours asleep.
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If there are some sleep/allergy/breathing related topics you would like us to cover in our next blog please get in touch – we love hearing from you!
Resources: WebMD, Britishsnoring.co.uk, tuck.com, sleepcycle.com, livescience.com