Light vs Deep Sleep: A Sleep Showdown of 8 Differences and Similarities
Published February 4, 2023.
So many factors influence how much sleep we need and what type of sleepers we are: genetics, lifestyle, health, and sleep disorders. These impact why some of us tend to be deep sleepers and others tend to be light sleepers.
7-9 hours of sleep is considered the best, and most experts consider this a necessity, rather than a recommendation. Making sure that you get adequate deep sleep is especially important as these are the stages that impact cognitive, physical, and mental health.
Read on to learn more about the differences and similarities between light and deep sleep and why you need to know.
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The 5 Sleep Stages
We have 5 stages of sleep that are usually numbered 1-4 and REM (1).
REM is "rapid eye movement," when we tend to dream—though we do dream in light and deep sleep stages as well. Stages 1-4 are NREM, or "non-rapid eye movement."
We usually complete three to five 90-120 minute full sleep cycles per night, rotating between the NREM and REM stages. However, the length of these stages can vary, with the first often being the shortest.
Stage 1: Pre Sleep
This is the stage where we drift from awake to asleep and usually lasts between one and five minutes. It is easy to wake someone in this stage of sleep, but, if they are not disturbed, they will quickly move on to the next stage and then not return to this phase unless the sleep cycle is disturbed, such as the person waking up.
Stage 2: Light Sleep
This is when our muscles relax, breathing and heartbeat slow, and we are moving towards a steadier sleep. Our body temperature drops, and there are often short bursts of brain activity that help us resist being woken by external stimuli. This stage lasts between 10 and 25 minutes in the first cycle and gets progressively longer during the night.
Stage 3: Deep Sleep
During this stage, our breathing, heartbeat, and body temperature are at their lowest levels during the night, when our muscles are completely relaxed.
Stage 4: Deepest Sleep
This is the sleep stage where healing happens: tissue repair and growth occur, hormones are released and re-balanced, and cellular energy is restored. During this stage, we consolidate our memories as well. Delta brain waves are common during this period, and this is part of what experts believe is restorative. There is also some evidence that creative thinking and memory consolidation occur during this phase (2).
REM Sleep: Dream Phase
This is the stage of sleep where most dreams occur. The first cycle begins about 90 minutes after we fall asleep (in most people), followed by a new cycle every 90 minutes throughout the night.
During REM sleep, breathing, heart rate, and blood pressure rise to almost the level they are at when we are awake. During this stage, the body experiences temporary paralysis with the exception of the muscles that control breathing and eye movement. REM sleep is essential to cognitive function, including memory consolidation and learning (3).
4 Key Differences Between Deep Sleep and Light Sleep
- Brainwaves slow down dramatically
- Stages 3 and 4
- 10%-25% of total sleep
- These stages can be hard to reach
- Brainwaves slow down only slightly
- Stages 1 and 2
- 50%-60% of total sleep
- These stages are easy to achieve
4 Similarities Between Deep Sleep and Light Sleep
- Both are NREM sleep stages
- Both types of sleep are essential for restorative sleep
- Dreams occur in both types of sleep
- Both types of sleep are crucial for physical and mental health
Why Is Deep Sleep Important?
Although all stages of sleep are important, deep sleep has the largest impact on our health. Deep sleep is the sleep that makes us feel refreshed when we wake in the morning so if you are not waking up refreshed, you might not be getting enough deep sleep.
Not getting enough deep sleep comprises your immune system and increases your risk of heart disease and stroke.
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Can You Increase Deep Sleep?
As deep sleep is essential to cognitive, mental, and physical health, finding ways to make sure that you are getting an appropriate amount of deep sleep is essential.
Eating a healthy diet is just one of the many ways that you can improve deep sleep (4). Resist having a nightcap as, though the alcohol often has a sedative effect, it disrupts sleep cycles and can impact the quality of sleep.