The normal sleep cycle consists 4 stages of non-REM sleep cycles and 1 cycle of REM (Rapid Eye Movement) sleep throughout the night. When your sleep cycles are disturbed, you wake up feeling tired and difficulty concentrating during the day.
- NREM sleep. These four stages start from very light sleep during Stage 1 down to very deep sleep in Stage 4. Throughout NREM sleep, there is little muscle activity and it is very difficult to wake someone in stage 4 sleep. Deep sleep helps to restore your body and muscles from stresses of the day
- REM sleep: This is the stage of sleep in which most dreaming occurs and our eyes are thought to move in relation to the visual images of our dreams
Each cycle lasts around 90 minutes consisting of the 5 stages of sleep.
During the night, the amount of time spent in each stage varies; we spend more time in stages 3 & 4 in the beginning of the night and more time in REM stage towards the morning. Increasing age also changes our sleep patterns as we require less time sleeping while babies spend 50% sleep time in REM stage.
Our internal clock situated at the hypothalamus dictates our normal circadian rhythm which helps us stay awake during the day and gets us ready to sleep at night. However, this rhythm can be disturbed by travelling through different time zones (jet lag) or doing shift work. Psychological issues such as stress or depression can also disturb your sleep pattern.
How can sleep deprivation affect health or quality of life?
- Good sleep is important for healthy brain function such as thinking, memory, learning, decision making and creativity
- Important for physical health such as:
- Healing and repair of the body
- Growing in children
- Maintaining balance hormones (growth hormone)
- Sleep deprivation results in poor blood sugar control
- Obesity risk in sleep deficiency
- Ensuring good immune system
Common Sleep Disorders
Common sleep disorders include insomnia and Obstructive Sleep Apnoea (OSA)
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Insomnia is the inability to fall asleep or maintain sleep or wake up too early in the morning and feeling tired. The usual time to fall asleep is 10-20 minutes.
The causes can be:
- Primary (not related to any medical issues)
- Secondary (related to medical issues such as depression, stress, anxiety, chronic pain from arthritis, asthma, cancer or side-effects of medication)
Treatment involves practising good sleeping habits such as:
- Going to bed (and waking) at the same time every night
- Follow the same routine to help you relax before sleep
- Avoid playing with light emitting devices just before sleep as they stimulate the brain and makes it harder to fall asleep
- Try to avoid a heavy meal prior to bedtime
- Avoid caffeine 3-4 hours before sleep
- Avoid vigorous exercise close to bedtime as the adrenaline release stimulates the brain and body making it difficult to fall asleep
- Obstructive sleep apnoea (OSA)
OSA is the most common type of sleep apnoea. Around 15-20% of adults experience OSA and it is associated with being overweight, older age groups, smokers, rhinitis, pharyngeal reflux and in males. During sleep, our muscle tone relaxes and the airway lumen diminishes which requires more respiratory effort. This increase in respiratory effort results in negative airway pressure causing the airway soft tissue to flop back and obstruct the airway.