Following up on last month’s article, STANISLAS LAJUGIE shares details about our sleep patterns and what is needed to create a really healthy sleep routine.
If you want to follow your dreams, go to sleep early
In the 1950s, after conducting experiments on rats that were later confirmed on humans, scientists discovered that we did not have a continuous and consistent pattern of brainwave activity during sleep. Instead, the brainwave patterns fluctuated between periods of higher-frequency waves, similar to wakeful brain activity, and periods of low-frequency waves, typical of deep sleep.
The sleep periods resembling wakeful states were characterized by rapid and irregular eye movements, and dreams. This type of sleep was called rapid eye movement or REM sleep. During the other periods, brain activity was slow and the body completely relaxed with no movement of the eyes. This state was called deep or NREM sleep.
During NREM sleep, the body repairs itself. Tissues regenerate, the immune system rejuvenates, and energy levels replenish. The brain consolidates memories and learning from the day, and expels neurotoxins.
Indeed, deep NREM sleep is the brain’s cleanup phase. Brain activity and blood circulation decrease, permitting the glymphatic system (clears waste products and toxins from the brain) to facilitate the exchange of cerebrospinal fluid (CSF) and interstitial fluid (ISF) in the brain. During this phase, ISF volume increases by 60%, flushing the brain and eliminating waste.
Research reveals that the glymphatic system also aids memory consolidation, potentially explaining sleep’s role in brain health. Prolonged sleep deprivation can impair this, allowing toxic waste buildup that contributes to cognitive decline and neurological disorders, including Alzheimer’s.
The initial stage of sleep and transitory phases are light REM sleep, followed by progressively deeper states. During REM sleep, brain activity heightens, accompanied by rapid eye movement. This phase is characterized by dreams and flashbacks, testing all scenarios, and allowing vital processing and memorization of emotions.
The World Health Organization recommends seven to nine hours of sleep for adults, though individual needs may differ. Sleep quality also matters. A fulfilling night’s sleep contains multiple cycles of deep sleep and light sleep, essential for physical and mental revitalization. An average sleep cycle spans 90 minutes, with around four to five cycles in a 24-hour span for optimal rejuvenation. Uninterrupted sleep, devoid of frequent awakenings, is equally crucial.
Quality of sleep is not only about how long we sleep, but also when we sleep. The circadian rhythm is the natural, internal process that regulates the sleep-wake cycle and various physiological and behavioral processes in living organisms, including humans, on a daily basis. The main gland that regulates the circadian rhythm is the pineal gland. Located deep within the brain, the pineal gland plays a crucial role in the regulation of various physiological processes, including the sleep-wake cycle and the production of the hormone melatonin.
The pineal gland receives signals from a cluster of neurons in the hypothalamus (SCN) that acts as the body’s master biological clock. The SCN receives information about the external light-dark cycle through the eyes’ retinal cells, which then communicate this information to the pineal gland.
When darkness falls, the SCN signals the pineal gland to increase its production of melatonin, and the rise in melatonin levels promotes drowsiness and prepares the body for sleep. As morning approaches and light levels increase, the SCN signals the pineal gland to decrease melatonin production, promoting wakefulness. In this way, the pineal gland’s secretion of melatonin serves as a key component of the circadian rhythm, helping to align internal biological processes with the external day-night cycle.
What is your sleep health?
When we sleep has an effect on our circadian rhythm. If we go to sleep after 11 p.m., we will not get the longest duration of NREM sleep, in particular N3 (very deep sleep), the stage most associated with physical restoration and recovery. During N3 sleep, the body engages in critical processes like cell repair, growth, and immune system support, and the brain’s glymphatic system is most active. Deep sleep also plays a vital role in memory consolidation, particularly for declarative memory (facts, events, experiences). Emotional processing and regulation are also linked to deep sleep, helping to modulate emotional responses and potentially reset the brain’s emotional state.
An average sleep cycle spans 90 minutes,
with around four to five cycles in a
24-hour span for optimal rejuvenation.
Sleeping early supports metabolic functions and helps regulate hormones involved in appetite control, metabolism, and stress response. Disrupting these processes by sleeping late can potentially lead to metabolic imbalances and increased stress.
Melatonin secretion increases in the evening, promoting sleepiness. If we’re awake and exposed to light when our bodies expect darkness, melatonin levels may remain elevated, leading to feelings of fatigue, and a mismatch between our internal clock and external environment. Instead of feeling energetic in the morning, melatonin presence may persist, making it difficult to wake.
Not getting the necessary NREM sleep can contribute to mood disturbances, like irritability, mood swings, and potential mental health issues.
In summary, when we consistently go to bed after 11 p.m., we miss out on the critical early-night NREM sleep stages, which can have a cascading impact on various aspects of our health and functioning.
If you need to make adjustments to your sleep schedule, it’s recommended to do it gradually over a period of time, to allow your body to adapt to the changes.
Meditation: a gateway to enhanced sleep and brain function
To become a sleep champion requires a healthy lifestyle: going to sleep early and for long enough, a balanced work life, regular exercise, reduced coffee and tea consumption, a timely and light diet.
Additionally, meditation brings many benefits for sleep quality and brain functioning, including stress reduction1, enhanced sleep quality2, circadian rhythm alignment3, and daytime vitality4.
Moral of the story?
The lesson is clear: sleep’s intelligence far surpasses our comprehension. Ignoring it could hasten our journey toward an early end. In the grand mosaic of existence, sleep is not a waste of time for the busy, but a vital need. Our physical and mental well-being dance to its rhythm, and meditation may well be the conductor guiding us to harmonious rest.
1 Jindal et al., 2016; Tang et al., 2015; Winbush et al., 2007; Ong et al., 2008.
2 Black et al., 2015; Gong et al., 2016.
3 Burke et al., 2015.
4 Colzato et al., 2015; Mrazek et al., 2013.