Healthy sleep occurs in four stages during each sleep cycle, but which sleep stage is best overall and why? When we talk about whether we are getting quality sleep, we tend to focus on the amount of sleep we get each night, but the sleep stages are essential to this conversation

Of course, it is important to know how many hours of sleep you are getting, and most adults need between seven and nine hours per night However, sleep duration is only one aspect of sleep quality, as is whether you are sleeping on a mattress that is optimal for your body and sleeping position In fact, restorative sleep is due to the relationship between several key sleep stages that our bodies cycle through during the night

Many of us have heard about REM (rapid eye movement), the "dreaming" stage of sleep, but this stage actually accounts for only about a quarter of our nightly rest Technically, there are four stages of sleep," explains Dr Chris Winter, neurologist, sleep expert, and host of the Sleep Unplugged podcast But which stage of sleep is best, and why, as we look back at Sleep Awareness Week 2024

When we think of sleep, we tend to think of it as either being awake or asleep However, there are four stages of sleep, each of which plays an important role in ensuring adequate rest Sleep deprivation affects the cardiovascular system, mood, hormones, blood sugar, weight, and inflammation"

Because quality sleep supports our overall health, it is important to understand the critical role each sleep stage plays Sleep includes three non-REM sleep cycles and one REM sleep cycle Here, Dr Winter describes each:

N1: The transitional phase between awakening and falling asleep, which takes about 5% of the night, or just a few minutes N2: The lightest sleep phase, but the longest, occupying about half of the night The longest sleep cycle is called N2, the second sleep stage, and is actually light sleep," Dr Winter explains N3: This stage is where we get our deepest rest, but only about a quarter of the night, or one to two hours REM sleep (rapid eye movement): Known as the dream sleep stage, this stage accounts for only about 25% of the night and is important for maintaining focus, memory, and concentration

So how do we cycle through the sleep stages? Dr Ally Hare, consultant in sleep medicine at the Royal Brompton Hospital in London, explains, "Sleep episodes begin with a brief N1 stage, followed by N2 and N3 stages, and finally stage 4, REM sleep"

"However, REM sleep does not continue throughout the rest of the day; in fact, it is a cycle of non-REM and REM sleep"

"The REM sleep stage is the most important stage of the sleep cycle

Here Dr Hare clarifies why each sleep stage is important to our overall wellbeing:

N1 - the lightest sleep stage, where we fall asleep and brain activity begins to slow down

N2 - deeper sleep than stage 1, but still light sleep During this stage, the heart rate and body temperature begin to decrease and the patient is less likely to awaken than in N1 This stage appears to be important for memory and learning

N3 - Deep sleep is important for maintaining a healthy immune system and lymphatic system (essentially the brain's waste removal system) It is also important for creative thinking and problem solving

"This stage is restorative, when our bodies release the most growth hormones, and it is the sleep that ultimately makes us feel less sleepy when we wake up," says Dr Winter

REM sleep - this is where we dream the majority of the time The diaphragm maintains our breathing and the eye muscles produce the rapid eye movements we experience during sleep [The diaphragm maintains our breathing and the eye muscles produce the rapid eye movements we experience during sleep This paralysis is thought to be nature's way of preventing us from executing dreams REM sleep is important because its interaction with the preceding non-REM sleep stage is thought to be critical for memory formation and management of the finite memory areas of the brain

Experts agree that each sleep stage plays an important role in the overall quality of sleep Dr Hare explains, "It is believed that the most restorative work occurs in the deep sleep stage, N3"

"This is where our lymphatic system comes into play It is an important network that removes waste products in the form of soluble proteins and metabolites from the central nervous system and provides essential glucose and lipids to the brain's central nervous system

It also supplies the brain with neuromodulators such as dopamine and serotonin to help regulate mood During deep sleep, the lymphatic system constantly filters toxins from the brain, including toxins associated with the accumulation of amyloid plaques, which are believed to cause Alzheimer's disease

When sleep is disturbed, cognitive function is impaired Dr Hare explains, "The effects of sleep deprivation are more far-reaching than simply skipping a sleep cycle"

So how can we avoid disrupting our natural sleep cycle? Changing your bedtime does not "skip" your sleep cycle

"But waking up earlier than usual does mean that you may miss some REM sleep

"So having a regular sleep-wake schedule is important to keep your circadian rhythms in sync