Stages of sleep: Understanding your sleep cycle

We cannot imagine how our lives would be without sleep. A healthy and regular sleep routine helps the body and mind to manage day to day stressors efficiently, improves mood, memory and concentration, prevents sickness by strengthening immunity, clears toxins in the brain and reduces the production and sustenance of stress hormones. Good quality sleep on a daily basis is absolutely imperative for body and mind to function optimally.

To understand more on why sleep is crucial, try to think of your body as a factory carrying out important functions and as we sleep, your body begins its night shift work. Sleep allows the brain and body to eliminate toxins from the body. According to research done, using mice, by National institute of neurological disorders and strokes- the space between the cells expands during sleep, aiding in extermination of toxins that are build up during waking hours. Not allowing the body to efficiently and effectively complete its detoxifying process can have various adverse effects on physical and mental health.

Unhealthy sleep patterns or poor-quality sleep can wreak havoc on every system of the body. Knowing why sleep is so important is critical to prevent lifestyle diseases and disorders. So, let us look at some of the indicators of poor-quality sleep that can help you realize whether or not you are sleeping poorly.

Indicators of poor-quality sleep:

• Not feeling refreshed after waking
• Excessive daytime sleepiness
• Puffy, red eyes, undereye dark circles
• Lethargic/fatigued most of the day
• Mood swings, irritability
• Emotional eating/stress eating
• Frequent yawning (relying on caffeine to get through the day)
• Poor sleep latency (taking more than 30 minutes to fall asleep)
• Frequent sleep disturbances, for instance, waking in the middle of the night and finding difficulty falling back to sleep
• Forgetfulness or inability to concentrate
• Poor immunity

Two main processes that regulate sleep

The two main processes that help in determining the sleep and wake time are Circadian rhythms and homeostatic sleep drive.

Circadian rhythms: These are natural sleep-wake patterns accompanied by physical, mental and behavioural changes that occur across a 24-hour period. Controlled by a master clock which responds to light/dark cues, circadian rhythms promote and facilitate wakefulness during the day and sleepiness at night.

Furthermore, a tiny endocrine gland located in the brain called pineal gland releases sleep hormone called Melatonin, this gland produces highest levels of melatonin in the absence of light and decreases in the presence of it. In other words, melatonin levels are high in your blood during day and lowest during night time. Hence, regulating the circadian rhythm/biological clock.

Homeostatic sleep drive: Pressure for sleep builds up after we have woken up and continues to build until we fall asleep at night. With every single waking hour this drive, gets stronger and when it reaches a certain point it encourages you to sleep.

Understanding sleep cycles

There are four stages of sleep that are divided into two recurring phases: non-REM and REM (Rapid eye movement).

N-REM stage 1/ N1 that lasts for 1-5 minutes, is also referred to as a transitional period between wakefulness and sleep. This is the lightest stage of sleep, wherein everything starts to slow down including your brain waves, heartbeat, eye movement and muscle reactivity. It is basically a dozing off state and is easy to wake someone while in this stage.

N-REM stage 2/ N2. In this stage the body temperature falls and heart rate and breathing slow down even further, On the whole, the brain waves slow down, but there is a presence of short bursts of activity known as the sleep spindles that help you resist being woken up by external events. Sleep spindles are also known for their role in consolidating memories. This stage prepares you for the deepest part of sleep and lasts between 10-60 minutes.

N-REM stage 3/ N3 (Deepest sleep). This stage is also referred to as the slow-wave sleep, and is considered as the deepest part of sleep. The heart rate further drops, and delta sleep waves (slowest brain waves) are produced in the brain. There would be no eye movement or muscle activity during this stage.

Deep sleep has physical and cognitive health benefits such as, cell regeneration, restoration, growth, immune system strengthening, bone and muscle tissue building. It also contributes to creativity, problem solving and learning processes. This is also a stage where sleep walking, bedwetting and nightmares happen. This stage lasts around 20-40 minutes. If someone is woken up from this stage, he/she may experience a condition called sleep inertia (a state of grogginess, disorientation and drowsiness).

REM Stage R: The fourth phase is called the REM (Rapid eye movement) sleep which begins 90 minutes after falling asleep and lasts for about 10-60 minutes, this is the phase wherein we dream. In addition, brain becomes more active, breathing and heart beat is faster, eyes move rapidly, memory consolidation occur (important stage for the learning process), there is rapid movement of eyes and body muscles become completely immobilized.

Some of the factors that can cause sleep cycle disturbances

• Sleep disorders, such as insomnia, sleep apnoea, restless leg syndrome, narcolepsy, delayed and advanced sleep-wake phase disorder, REM sleep behaviour disorder, non-24- sleep wake disorder, shift work disorder
• Old age
• Nocturia (Frequent need to urinate during night time)
• Mood disorders such as depression and bipolar disorder and its medications
• Chronic pain, Parkinson’s disease, Alzheimer’s disease, Obesity
• Poor lifestyle habits like lack of exercise, excessive intake of alcohol, nicotine and caffeine

Sleep stages are extremely crucial part of our physical, emotional and mental health development. Getting sufficient amount of sleep is vital for health enhancing bodily states like digestion, immunity, growth, restoration and learning process. Improving sleep hygiene is a key step to have a healthier and an effective sleep cycle.