Le rôle du sommeil dans notre vie quotidienne
Daisy Flora
The Science of
Sleeping Better
Sleep is not a passive state. It is an active, complex biological process in which the body repairs tissue, consolidates memory, regulates hormones, and renews its immune defenses. The conditions under which sleep occurs — temperature, moisture, sound, light — directly shape its quality and depth. Of all these factors, the thermal and textile environment of the bed is among the most actionable and the most overlooked.
A landmark 2024 systematic review published in the Journal of Sleep Research (Li et al.) examined the full body of evidence on how sleepwear and bedding fiber types affect sleep quality. The conclusion is clear: fiber composition matters, and the differences are measurable — not merely subjective.
The Circadian Temperature Curve
Core body temperature (CBT) follows a predictable circadian rhythm: it peaks in the late afternoon and falls in the evening, reaching its minimum around 4 a.m. before rising again toward morning. Sleep onset is tightly coupled to this decline — the body cannot enter sleep efficiently unless heat is successfully dissipated from its core to its periphery (hands, feet, face).
Research by Okamoto-Mizuno & Mizuno (2012) in the Journal of Physiological Anthropology demonstrated that bedding material plays a measurable role in supporting or hindering this heat dissipation. Fabrics that trap heat and moisture beneath the body create a microclimate that works against the natural thermoregulatory curve, increasing sleep-onset latency and reducing time in restorative deep sleep.
TENCEL™ Lyocell, by contrast, actively facilitates heat exchange. Its highly breathable fiber structure allows air to move through the textile, and its moisture-wicking capability removes perspiration before it creates a humid, heat-retaining layer between skin and fabric.
"Sleep duration is extended when bedtime occurs on the falling limb of the core body temperature curve. Bedding that supports this decline directly prolongs restorative sleep."
Sleep-Onset Latency & Fabric
One of the most practical metrics in sleep science is sleep-onset latency (SOL) — the time it takes to fall asleep after lying down. A study published in PLOS ONE (2016) — "The effects of fabric for sleepwear and bedding on sleep at ambient temperatures of 17°C and 22°C" — demonstrated that bedding fabric significantly affects SOL. Participants sleeping on natural, breathable fabrics fell asleep measurably faster than those on fabrics with poor moisture and heat management.
A 2015 study in the Journal of the Japan Research Association for Textile End-Uses specifically examined the effect of pajama material on sleep onset under warm humid conditions — one of the most common causes of poor summer sleep in adults. The findings confirmed that moisture management capacity in textiles is a primary determinant of how quickly and how deeply sleep is initiated in adverse thermal conditions.
Deep Sleep, REM & Recovery
Deep sleep (slow-wave sleep) is the phase in which the body produces the majority of its growth hormone — essential for cellular repair, muscle recovery, and immune reinforcement. REM sleep is the phase associated with emotional regulation, memory consolidation, and creativity. Both phases are disrupted by thermal discomfort and excessive nocturnal sweating.
The 2004 study by Lee et al. in The International Journal of Neuroscience found that multi-functional fabrics engineered to optimize sleep microclimate produced a statistically significant increase in deep sleep stages and growth hormone secretion compared to standard bedding. A stable, comfortable microclimate removes one of the primary triggers of micro-arousals — the brief, often unconscious wakings that fragment sleep architecture.
TENCEL™'s 50% greater moisture absorption compared to cotton means it handles the body's nighttime perspiration more effectively, preventing the accumulation of moisture that would otherwise elevate skin temperature and trigger these micro-arousals.
What 63% of French Adults Don't Know
A 2020 survey by the Institut National du Sommeil et de la Vigilance found that 25% of French adults report unsatisfactory sleep quality — and 63% of the French population reports sleeping poorly. Of these, the vast majority have never considered that their bedding fiber type could be a contributing factor.
The research is unambiguous: investing in bedding made from high-performance, breathable, moisture-wicking fibers like TENCEL™ Lyocell is one of the most evidence-backed interventions available for improving sleep quality — without medication, supplements, or lifestyle overhaul.
- Core body temperature must drop 1–2°C for sleep onset — bedding can help or hinder this
- Breathable, moisture-wicking fabrics reduce sleep-onset latency (Journal of Sleep Research, 2024)
- Thermal discomfort triggers micro-arousals that fragment sleep architecture
- TENCEL™ absorbs 50% more moisture than cotton, reducing disruptive nighttime sweating
- Optimized sleep microclimate increases deep sleep and growth hormone secretion
- 63% of French adults report poor sleep — bedding fiber type is an underexplored variable
- Li, Y. et al. (2024). How do sleepwear and bedding fibre types affect sleep quality: A systematic review. Journal of Sleep Research, 33, e14217. Wiley / European Sleep Research Society.
- Okamoto-Mizuno, K. & Mizuno, K. (2012). Effects of thermal environment on sleep and circadian rhythm. Journal of Physiological Anthropology, 31, 14. PMC/PubMed.
- Okamoto-Mizuno, K. et al. (2015). Effects of different pajamas material on sleep onset period under mild humid heat exposure. Journal of the Japan Research Association for Textile End-Uses, 56(3), 56–63.
- Haskell, E.H. et al. (2016). The effects of fabric for sleepwear and bedding on sleep at ambient temperatures of 17°C and 22°C. PLOS ONE / PubMed, PMID 27217803.
- Lee, M.S., Song, J. et al. (2004). Effect of multi-functional fabric on sleep stages and growth hormone levels during sleep. The International Journal of Neuroscience, 114(7), 795–804.
- Institut National du Sommeil et de la Vigilance (2020). Enquête nationale sur le sommeil des Français. Rapport INSV, Paris.