Sleeping position should be considered as an etiological factor in the formation of wrinkles. All the subjects in the study exhibited oblique and horizontal lines and slept in the prone position “with their faces buried in the pillow.”

Sarifakioğlu N, Terzioğlu A, Ates L, Aslan G. A New Phenomenon: “Sleep Lines” on the Face. Scand J Plast Reconstr Surg Hand Surg. 2004;38(4):244-7.

Wrinkles occur where fault lines develop in aging skin. Those fault lines may be due to skin distortion resulting from facial expression or may be due to skin distortion from mechanical compression during sleep. Expression wrinkles and sleep wrinkles differ in etiology, location, and anatomical pattern. Compression, shear, and stress forces act on the face in lateral or prone sleep positions. We review the literature relating to the development of wrinkles and the biomechanical changes that occur in response to intrinsic and extrinsic influences. We explore the possibility that compression during sleep not only results in wrinkles but may also contribute to facial skin expansion.

Anson G, Kane M, Lambros V. Sleep Wrinkles: Facial Aging and Facial Distortion During Sleep. Aesthet Surg J. 2016 Sep;36(8):931-40.

15 subjects aged 26-42 years, both genders, used a transparent PVC pillow filled with air to demonstrate mechanical forces and deformations of face due to sleeping on a pillow. Using a podometer (integrated fluorescent luminaire lamp), authors observed facial deformities including crow’s feet fine lines, lines around mouth, flattening of forehead, blunting of nasofrontal angle, melolabial and nasolabial folds.

Poljsak B, Godic A, Lampe T, Dahmane R. The Influence of the Sleeping on the Formation of Facial Wrinkles. J Cosmet Laser Ther. 2012 Jun;14(3):133-8.

The duration of sleep and the position of the face while resting on a pillow have a negative impact on the facial skin appearance and may lead to the formation of sleep wrinkles. Sleep lines occur when there is repetitive, long-term tension on the facial skin, which pushes or pulls the skin in a direction that is perpendicular to the direction of the muscles of the face. These lines tend to be more vertically oriented than expression lines and can be found on the forehead, around the eyebrows, the eyes, the cheeks, the chin, and the nasolabial folds. Our studies revealed that the average reduction of wrinkles in total investigated area of the face (expressed as the density of wrinkle per surface skin) was approximately 12% after 28 days of sleep on a specially-designed pillow.

Poljsak B, Godic A, Starc A, Dahmane R. The Neglected Importance of Sleep on the Formation and Aggravation of Facial Wrinkles and Their Prevention. J Cosm Dermatol Scie and Applic. 2016 Jun;6(3).

This interview provides an overall review of how sleeping causes wrinkles and how contributing factors like skin moisture, smoking, etc. play a role.

Mohammed Y, Phan K, Silva V. Sleep Wrinkles are Real. Here’s How They Leave Their Mark. The Conversation. May 2024. theconversation.com

*Based on published interview, not peer-reviewed publication.

Gradual reduction of elastic fibers in aging significantly reduces the skin’s ability to bend, prompting an up to 4-fold reduction of its stability against wrinkling, thereby explaining the role of these fibers in skin aging.

Kruglikov I, Scherer P. Skin Aging as a Mechanical Phenomenon: The Main Weak Links. Nutr Healthy Aging. 2018 Jun 15;4(4):291-307.

Applying mechanical pressure to the skin can induce various changes in its microenvironment that potentially lead to pathological alterations, such as inflammation, ischemia, necrosis, proliferation, hyperkeratosis, impaired regeneration, atrophy, or other injurious reactions.

Chien W, Tsai T. Pressure and Skin: A Review of Disease Entities Driven or Influenced by Mechanical Pressure. Am J Clin Dermatol. 2024;25(2):261-80.

Sleep line location correlates with underlying SMAS (superficial musculoaponeurotic system) attachments. When the overlying skin is compressed and distorted during sleep, wrinkles form at these tethering sites.

Fulton JE, Gaminchi F. Sleep Lines. Dermatol Surg. 1999 Jan;25(1):59-62.

Laxity of the SMAS (superficial musculoaponeurotic system)—the subcutaneous anchoring tissue—increases with age (r = 0.72, P < 0.001), compounding the skin’s vulnerability to mechanical deformation [such as occurs during sleep]*.

Okuda I, Yoshioka N, Shirakabe Y, Akita K. Basic Analysis of Facial Ageing: The Relationship Between the Superficial Musculoaponeurotic System and Age. Experimental Dermatology. 2019 Feb;28 Suppl 1:38-42.

*Clinical inference

As people age, there is a progressive disappearance of sleeping in the prone (stomach sleeper) position and increasing preference for lateral (side sleeper—especially right side) positions, along with fewer position shifts per hour (from approximately 4.4 shifts/hour in children to about 2.1 shifts/hour in the elderly). This means older adults spend longer periods in a single lateral position [increasing cumulative compressive force exposure]* on one side of the face.

De Koninck J, Lorrain D, Gagnon P. Sleep Positions and Position Shifts in Five Age Groups: an Ontogenetic Picture. Sleep. 1992 Apr;15(2):143-9.

*Clinical inference

Population surveys confirm that most adults prefer the lateral sleep position, with females more likely to sleep laterally than males.

Bjorvatn B, Mrdalj J, Saxvig IW, et al. Age and Sex Differences in Bedroom Habits and Bedroom Preferences. Sleep Medicine. 2017 Apr;32:157-161.

3D pressure discomfort threshold maps of the face—particularly the areas around the nose, mouth, chin-jaw, cheek, and cheekbone—had the lowest pressure discomfort thresholds, likely due to proximity of nerves, blood vessels, and soft tissue. These are precisely the areas most compressed during lateral and prone sleep, suggesting that the face is both biomechanically vulnerable and subjectively sensitive to compression.

Smulders M, van Dijk LMN, Song Y, Vink P, Huysmans T. Dense 3D Pressure Discomfort Threshold (PDT) Map of the Human Head, Face and Neck: A New Method for Mapping Human Sensitivity. Appl Ergon. 2023 Feb;107:103919.

Yang W, He R, Goossens R, Huysmans T. Pressure Sensitivity for Head, Face and Neck in Relation to Soft Tissue. Appl Ergon. 2023 Jan;106:103916.

Compression-induced tissue damage (such as occurs from pressure of the face pressing into the pillow) correlates with maximum shear strain at the bone-tissue interface, with a reproducible monotonic increase in damage once a strain threshold is exceeded.

Ceelen KK, Stekelenburg A, Loerakker S, Strijkers GJ, Bader DL, Nicolay K, Baaijens FPT, Oomens CWJ. Compression-Induced Damage and Internal Tissue Strains are Related. J Biomech. 2008 Dec 5;41(16):3399-404.

The subcutaneous fat of the cheek is organized into discrete compartments (medial, middle, and lateral temporal-cheek fat) separated by septal barriers. Chronic compression over the zygoma (cheekbone) could preferentially thin or remodel the fat compartment directly overlying the bone, creating a visible contour irregularity. The fibroadipose connective (dense fibrous) tissue system of the cheek—with vertically oriented fibrous septa (strands) connecting dermis to SMAS—progressively thins from the preauricular region (in front of the ear) toward the nasolabial fold (smile line). This architecture means that tissue over the zygomatic eminence (most prominent part of the cheekbone) is relatively thin and directly tethered (tied down) [making it particularly vulnerable to compression-induced remodeling (pressure points)]*.

Rohrich RJ, Pessa JE. The Fat Compartments of the Face: Anatomy and Clinical Implications for Cosmetic Surgery. Plast Reconstr Surg. 2007 Jun;119(7):2219-2227.

Macchi V, Tiengo C, Porzionato A, Stecco C, Vigato E, Parenti A, Azzena B, Weiglein A, Mazzoleni F, De Caro R. Histotopographic Study of the Fibroadipose Connective Cheek System. Cells Tissues Organs. 2010;191(1):47-56.

*Clinical inference

Repetitive compressive (pressure) and shear stresses cause measurable collagen remodeling. Skin subjected to cyclic compression/shear for 4 weeks showed 15.9–22.9% increases in collagen fibril (strand) diameter and 19.8–31.8% decreases in fibril density across all dermal layers. This represents a shift toward denser, stiffer connective tissue—exactly the kind of change that would create palpable resistance during needle or cannula insertion as occurs when fillers are placed.

Sanders JE, Goldstein BS. Collagen Fibril Diameters Increase and Fibril Densities Decrease in Skin Subjected to Repetitive Compressive and Shear Stresses. J Biomech. 2001 Dec;34(12):1581-7.

The fibrous connection beneath the dermis described during filler injection likely corresponds to thickened or fibrotic zygomatic cutaneous ligament (ZCL) fibers and surrounding tissue that have been remodeled by chronic sleep time compression. The ZCL itself is a dense collagen band extending from periosteum (tissue directly overlying the bone) to the dermis. [Chronic pressure, as occurs when the face is compressed by the pillow, would be expected to further stiffen this structure through TGF-β1-mediated collagen deposition]*.

Temizsoy Korkmaz F, Karip BZ, Ok F, Karip B. The Osteocutaneous Anchor of the Face: Zygomatic Cutaneous Ligament—Quantitative Topographic Map and Histologic Proof. J Craniofac Surg. 2025 Sep 3.

*Clinical inference

Patients with a predominant sleep side preference had significantly lower upper eyelid position (iMRD1) on the sleep side (p < 0.0004), indicating ipsilateral (same side) tissue descent.

Tran C, Choi D, Ko AC, Carter KD, Shriver EM. The Effect of Sleep Position Preference on Eyelid and Eyebrow Symmetry. Ophthalmic Plast Reconstr Surg. 2022 May-Jun;38(3):266-269.