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While the optimal sleep duration varies from person to person, approximately 7 hours is generally recommended. However, for busy modern individuals, securing long hours of sleep every day can be challenging. Consequently, there's been a recent shift in focus from merely "sleep duration" to "improving sleep quality," leading many to reconsider their bedding, including pillows.
Although adjusting bedding is believed to improve sleep quality, there isn't an abundance of scientific data specifically focusing on the relationship between bedding and sleep quality. Therefore, Brain Sleep conducted a study to verify the correlation between pillows and sleep.
What is Sleep Quality?
Sleep quality refers to various indicators used to evaluate sleep from the perspective of a healthy lifestyle. These indicators include "sleep duration," "stability (few awakenings during the night)," "appropriateness of time to fall asleep," and "satisfaction." The more of these indicators that are met, the closer one is to having high-quality sleep (restorative sleep).
What are REM and NREM Sleep?
To understand sleep quality, "REM sleep" and "NREM sleep" are indispensable. This section will explain REM and NREM sleep.
What is REM Sleep?
REM sleep is a sleep stage where the body is at rest, but the brain is active. Its distinctive name comes from the acronym for rapid eye movement, which occurs during this stage.
Typically, REM and NREM sleep alternate in 90-120 minute cycles. In nocturnal sleep, REM sleep generally follows NREM sleep (discussed below). As morning approaches, the duration of REM sleep increases, accounting for approximately 20% of the total night's sleep. Frequent dreaming is also a characteristic of REM sleep.
What is NREM Sleep?
NREM sleep is another sleep stage where both the brain and body are in a state of deep sleep. Its name is derived from "non-REM," meaning not REM sleep. This sleep stage appears immediately after falling asleep, and its duration shortens as morning approaches. Unlike REM sleep, dreaming is uncommon during NREM sleep.
NREM sleep is divided into four stages, from Stage 1, the lightest sleep, to Stage 4, the deepest sleep. In Stages 3 and 4, high-amplitude slow waves appear, and sleep deepens, reducing the level of consciousness. These two stages are referred to as slow-wave sleep.
The Relationship Between NREM Sleep and REM Sleep
As mentioned, NREM and REM sleep alternate throughout the night, with NREM sleep typically beginning first, followed by a transition to REM sleep. This cycle, while varying individually, usually occurs in 90-120 minute periods, repeating 4-5 times over the course of a night. The deepest state of sleep within this cycle is the first period of "NREM sleep."
What is the "Golden 90 Minutes" that Determines Sleep Quality?
At Brain Sleep, we refer to the first 90 minutes of the first cycle of NREM sleep, which is the deepest state of sleep, as the "Golden 90 Minutes." The first 90 minutes after falling asleep are so crucial that it's often said, "If the quality of sleep during the first 90 minutes is poor, the quality of sleep will remain poor no matter how many hours you sleep afterward."
The reason is that the deeper the sleep during these golden 90 minutes, the more "sleep pressure" (the desire to sleep) is released, and the better the balance of the autonomic nervous system and hormones is regulated.
Benefits of the "Golden 90 Minutes"
During the golden 90 minutes, five crucial physiological phenomena for sleep are particularly active: "rest for the brain and body," "memory organization and consolidation," "hormone balance adjustment," "immune system boost," and "removal of brain waste products."
Furthermore, growth hormone, which is said to play important roles in building essential body components like skin, bones, and muscles, as well as promoting cell proliferation, normal metabolism, and anti-aging, is secreted in greater quantities when one sleeps deeply and soundly during the golden 90 minutes. This also improves the quality of subsequent sleep, thereby regulating the overall sleep cycle.
Does changing your pillow really change sleep quality? Verifying the "pillow and sleep correlation"!
Brain Sleep conducted a study (※1) comparing our main product, the Brain Sleep Pillow (a pillow that helps the brain sleep), with a common functional polyurethane pillow widely used in Japan (hereinafter, "general functional pillow") to investigate how differences in pillow materials affect sleep quality.
※1 Subjects: 20 men and women in their 20s-50s. Test method: Crossover trial. Measured items: Activity level, brain waves, questionnaire evaluation using VAS (Visual Analogue Scale) method (OSA Sleep Inventory ※2)
※2 A general sleep evaluation method proposed by the Japan Association for Sleep Improvement, which statistically scales sleep sensation.
※3 In the following figures and tables, the Brain Sleep Pillow is referred to as "BS Pillow."
Verification Result 1: The proportion of "Golden 90 Minutes," the deepest sleep, increased.
In this verification, sleep stages during sleep were determined using an electroencephalogram.
As a result, the proportion of the deepest sleep (NREM sleep Stage 3) during the first cycle (golden 90 minutes), which influences sleep quality, significantly increased from 30.5±3.7% with the general functional pillow to 38.1±3.8% with the Brain Sleep Pillow.
Verification Result 2: Falling asleep and waking up improved, and sleep efficiency increased.
It was found that sleep efficiency improved due to a reduction in the time from getting into bed to falling asleep (sleep latency) and the time from final awakening to getting out of bed (bed exit latency).
Improved ease of falling asleep
Regarding sleep latency (the time it took to fall asleep after getting into bed), an indicator of ease of falling asleep, the Brain Sleep Pillow showed a significant reduction to 10.5±1.2 minutes, compared to 17.8±1.9 minutes for a general functional pillow.
Waking up feeling refreshed
Sleep latency (the time it took to fall asleep after getting into bed), an indicator of ease of falling asleep, significantly decreased to 10.5±1.2 minutes with the Brain Sleep Pillow, compared to 17.8±1.9 minutes with a general functional pillow.
Improved sleep efficiency
Bed exit latency (the time from final awakening to getting out of bed), an indicator of waking up refreshed, significantly decreased to 3.6±0.5 minutes with the Brain Sleep Pillow, compared to 8.4±0.9 minutes with a general functional pillow.
Due to the shortened sleep latency and bed exit latency, sleep efficiency (the proportion of time actually asleep while in bed) also significantly improved to 85.9±1.9% with the Brain Sleep Pillow, compared to 81.7±2.3% with a general functional pillow.
In other words, by using the Brain Sleep Pillow, both falling asleep and waking up improved, reducing the time spent idly in bed and thus increasing sleep efficiency.
Verification Result 3: Decreased sleep problems and felt more refreshed.
We compared subjective evaluations of sleep using the OSA Sleep Inventory, a psychological scale for assessing one's sleep upon waking.
As a result, among the following five sleep factors, the Brain Sleep Pillow scored significantly higher than a general functional pillow in "morning sleepiness," "sleep onset and maintenance," and "fatigue recovery."
- 1. Morning sleepiness (how clear-headed one is upon waking)
- 2. Sleep onset and maintenance (ease of falling asleep and stable sleep without mid-sleep awakenings)
- 3. Dreaming (whether sleep was deep and sound)
- 4. Fatigue recovery (whether one felt a sense of fatigue recovery and refreshment upon waking)
- 5. Sleep duration (whether sleep duration was sufficient)
In other words, it was found that issues such as morning sleepiness, difficulty falling asleep, and frequent awakenings decreased, and a sense of fatigue recovery was experienced.
From the Brain Sleep verification conducted this time, it was confirmed that using the Brain Sleep Pillow led to an improvement in subjective sleep evaluation, as well as an increase in the proportion of deep sleep during the golden 90 minutes, suggesting the possibility that changing pillows can lead to an improvement in sleep quality.
Pillows can change sleep quality! Three features of the Brain Sleep Pillow
Improve daily performance by focusing on sleep quality!
When sleep quality is high, your body and brain can rest efficiently within a limited sleep time, maintaining a clear mind the next morning. You can also expect benefits that contribute to work performance, such as improved concentration and a stable, less irritable mental state.
If you want to achieve the best sleep, why not try the Brain Sleep Pillow, designed with meticulous attention to both sleep medicine principles and materials?
