Science

Every neck has a Number. We can prove it.

Three studies. 1,604 sleepers. One finding that kept getting more specific.

The STRATA Sleep Sciences Institute was founded to answer a single question: is there a right height for a pillow, or only a less wrong one? Five years and 1,604 participants later, the answer is clear, and it is a number.

All research is conducted in-house and funded by STRATA Sleep Sciences.¹

11.3 nights

to your Number, on average.²

The Old Linen Mill, Pellham Ford

STRATA Sleep Sciences Institute

The STRATA Sleep Sciences Institute occupies the north wing of a former linen mill in Pellham Ford. It houses a 14-bed sleep laboratory, a pressure-mapping suite, a thermal chamber, and the only dedicated Void Layer inspection room in the industry. Its work is funded entirely by STRATA Sleep Sciences, which the Institute describes as ‘a conflict of interest we have chosen to be open about’.

“Subtract until it’s right.”

The Institute

Eleven scientists. One question.

Every study is designed, run and reviewed by people who have thought about necks longer than is usual.

Dr. Halcyon Reyes-Whitlock
Director
STRATA Sleep Sciences Institute
Spent eleven years measuring the angle of sleeping necks before concluding that every neck has exactly one correct number.
Dr. Ambrose Hesketh
Principal Scientist, Memory Materials
Linwood Foam Research Station
Developed Gen IV through Gen VII memory foam. Keeps a sample of every generation on his desk and refers to them by name.
Dr. Tobiah Fennimore
Head of Rebound
STRATA Sleep Sciences Institute
Measures rebound to the millisecond. Has personally compressed Layer 33 more than 40,000 times and defends its squeak.
Dr. Matthias Oyelaran-Cole
Director, Thermal Systems
Kessler-Brandt Thermal Laboratory
Designed the 31.2°C phase-change point after recording the cheek temperature of 900 calm volunteers.
Dr. Sunniva Aalto-Grieve
Reader in Fibre Science
Northmere College of Textiles
Counted 440,000 fibre clusters by hand for the first forty Micro-Down layers, then stopped, satisfied.
Dr. Marisol Uhde
Head of the Ovine Textile Unit
Northmere College of Textiles
Has felted wool for twenty-six years. Knows each of the cooperative flocks by sight and several sheep by temperament.
Prof. Edda Morrow
Chair, Department of Applied Loft
Harrowgate Polytechnic
Author of the standard textbook on pillow height, now in its ninth edition. Reviewed all three STRATA studies, sternly.
Dr. Yusuf Brannigan-Toll
Senior Fellow, Advanced Quilting
The Orrin Institute of Surface Science
Proposed seven of the eleven mechanisms for graphene quilting. Withdrew all seven. Remains optimistic.
Dr. Lionel Achterberg
Chair of Negative Space
Vellmar Academy
The world’s leading authority on intentionally empty materials. His office contains a desk, a chair, and nothing else, on principle.
Dr. Priya Castellane
Head of Cervical Biomechanics
The Calloway Institute for Posture
Designed the Cervical Alignment Index used in the LOFT-3 study. Can estimate a stranger’s Number from across a room, within four layers.
Prof. Odessa Kwan-Hartley
Professor of Comparative Rest
Harrowgate Polytechnic
Studies how sleep habits differ across 41 regions. Her finding that ‘everyone is tired’ remains her most cited.

Published research

Three studies.

STRATA-11, LOFT-3 and VOID-1. Each has been reviewed by someone outside the Institute.

STRATA-11

Nights to Number in a Free-Living Cohort

n = 1,204 · 120 nights · Lead: Dr. Halcyon Reyes-Whitlock · p < 0.0001

Participants who found their Number (%).³

Found their Number by Night 11: 94.7%
Mean nights to Number: 11.3
Median nights to Number: 9
Median Number: 52

We followed 1,204 adult sleepers through the STRATA Protocol in their own homes to measure how many nights it takes to find a Strata Number™. A Number was considered found when a participant met the Triple Quiet Rule: three consecutive nights at the same layer count with no neck discomfort on waking. 94.7% of participants found their Number by Night 11. The mean was 11.3 nights. The median was 9.

Method, results and conclusion

Method

Participants received a standard 100-layer STRATA, a Sleep Journal and a pair of Tweezers of Reflection. They began on Night 1 at 100 layers and removed layers each morning at their own discretion under the Standard Descent. Journals were collected weekly by a courier who was instructed not to ask how it was going.

Results

94.7% of participants (1,140 of 1,204) met the Triple Quiet Rule by Night 11. The remaining 5.3% (64 participants) were still journaling at the close of the observation window. Their mean, at time of writing, is 61.4 nights and rising, which raises the cohort mean to 11.3. The median Number was 52. No participant found a Number above 100.

Conclusion

Most sleepers find their Number in under two weeks. A small and committed minority are taking their time, and we support them.

LOFT-3

Cervical Alignment Across 100 Discrete Loft Positions

n = 312 · Laboratory, 6 nights per participant · Lead: Dr. Priya Castellane · p = 0.00003

Cervical Alignment Index (higher is better).⁴

Participants with a single optimum: 312 of 312
Mean CAI improvement: 41.7%
Range of optima: 3–97
Standard deviation: 17.4 layers

We measured cervical alignment in 312 sleepers at every layer count from 1 to 100, using overnight pressure mapping and a side-mounted posture camera. Every participant had exactly one layer count at which alignment was optimal. At that count, the Cervical Alignment Index improved by a mean of 41.7% over the participant’s previous pillow.

Method, results and conclusion

Method

Each participant slept six nights in the Institute’s laboratory. Layer counts were adjusted in 1-layer steps by a technician wearing soft-soled shoes. Alignment was scored on the Cervical Alignment Index (CAI), which measures the angle between the second and seventh cervical vertebrae against an ideal of 0°. Participants were not told their layer count, and most did not ask.

Results

All 312 participants showed a single, sharp optimum. Alignment worsened measurably at one layer above or below it. The mean improvement in CAI at the optimum, compared with each participant’s own pillow, was 41.7%. Optima were distributed across Numbers 3 to 97, with a median of 52 and a standard deviation of 17.4.

Conclusion

There is no average neck. There is, however, an average Number, and it is 52.

VOID-1

A Randomised, Double-Blind Trial of the Void Layer™

n = 88 · 28 nights · Lead: Dr. Lionel Achterberg · p = 0.049

Mean sense of space (0–10).⁵

Greater sense of space: 18.2%
Genuine Void, mean score: 7.8 / 10
Placebo Void, mean score: 6.6 / 10
Contents found in 704 Void Layers: 0

We randomised 88 sleepers to receive a STRATA in which the eight Void Layers were either genuine Void Layers or placebo Void Layers. Participants given genuine Void Layers reported an 18.2% greater ‘sense of space’ on waking. Both genuine and placebo Void Layers were empty.

Method, results and conclusion

Method

Placebo Void Layers were manufactured to the same dimensions and border tension as genuine Void Layers, and were likewise left empty. The only difference was that placebo Void Layers were made on a Tuesday. Neither participants nor researchers knew which layers they had. Sense of space was self-reported each morning on a 10-point scale.

Results

The genuine Void group reported a mean sense of space of 7.8 out of 10. The placebo group reported 6.6. The difference, 18.2%, was statistically significant. Physical examination of all 704 Void Layers in the trial found nothing in any of them.

Conclusion

Void Layers work. We do not know how. The Institute has opened a second trial, VOID-2, in which the placebo layers will be made on a Wednesday.

Clinical Study Recap. Thirty-five seconds, three studies, several unusually confident p-values.

Read the captions

STRATA-11. 1,204 sleepers. 94.7% found their Number by Night 11.
LOFT-3. 312 sleepers. Cervical alignment improved 41.7%. p = 0.00003.
VOID-1. 88 sleepers. Nothing helps. Slightly. Sleep quality 6.6 with Void Layers removed, 7.8 with them kept. p = 0.049.
11.3 nights to your Number, on average.

Outside opinion

Peer Review

Every study was reviewed by scientists outside the Institute, who were thanked and, where requested, left alone.

LOFT-3
“The methodology is sound. The result is so clean it made me uncomfortable. I have checked it four times and remain uncomfortable, and correct.”
Prof. Edda Morrow
Department of Applied Loft, Harrowgate Polytechnic
STRATA-11
“The authors should be commended for reporting the 5.3% who have not yet finished. I would like to be informed when they do.”
Prof. Odessa Kwan-Hartley
Department of Comparative Rest, Harrowgate Polytechnic
VOID-1
“I requested the raw data. I received an empty folder. On reflection, this was appropriate.”
Dr. Fenwick Ollerenshaw
School of Domestic Engineering, Calder Vale University
STRATA-11
“A rare study in which the participants appear to have enjoyed themselves. I am not sure how to account for this statistically.”
Dr. Imelda Marwood-Lyle
Centre for Rest and Recovery, Askett College

Try it

Cervical Alignment Simulator.

Choose a sleep position and a Number. Watch the spine respond.

Provisional Number

Confidence band: 47–57

Too high. The head is tilted 29° toward the ceiling. Remove layers.

The simulator is illustrative. Your spine is real and should be consulted in person.

Population

Everyone, so far.

Distribution of certified Numbers across all sleepers, 2022–2026.

Mean Number

Median Number

17.4 layers

Standard deviation

0.8%

Keep all 100 layers

28,114

Certified sleepers

Whitepaper

On the Existence of the Number

A technical summary of the STRATA-11, LOFT-3 and VOID-1 studies.

H. Reyes-Whitlock, P. Castellane, L. Achterberg, T. Fennimore, for the STRATA Sleep Sciences Institute. Third edition, September 2026.

On the Existence of the Number. Six pages, four figures, PDF.

Download the whitepaper

Reference

Glossary

The vocabulary of the Number.

Strata Number™: The layer count at which you meet the Triple Quiet Rule. Yours forever. Often shortened to ‘Number’.
Provisional Number: An estimate of your Number generated by the Builder or the Number Finder. Becomes a Number only when the Protocol confirms it.
Triple Quiet Rule: Three consecutive nights at the same layer count with no neck discomfort on waking. The Institute’s sole test for a Number.
Standard Descent: The default removal order: from the bottom of the stack upward, Layer 100 first. A sleeper with Number N sleeps on Layers 1 to N.
Loft Index: The height of your stack as a proportion of the full 100-layer stack. The full stack is Loft Index 100.0.
Rebound Coefficient: The speed with which a layer returns to its shape after compression, expressed in seconds. Reactive Latex: 0.3.
Number Drift: A change of more than three layers in a certified Number over a single season. Normal, documented, and covered by the Free Layer Audit.
Layer Fatigue: The gradual loss of a layer’s character over many years. Expected after approximately 3,000 nights. The layer is not sad. It is finished.
Pillow Plateau: Four or more nights at the same layer count without meeting the Triple Quiet Rule. Usually resolved by removing one layer, or by waiting.
Squeak Index: The audibility of a layer under compression, on a scale of 0 to 10. Layer 33 scores 8.9. Everything else scores below 3.5.
Neck Score: A nightly self-assessment from 0 to 100 recorded in the Sleep Journal. Converges toward the high nineties as you approach your Number.
Neck Comfort Index: The Institute’s modelled estimate of comfort at a given layer count, peaking at your Number. Shown as a gauge on our cross-section.
Contact Layers: Layers 1 to 10. The layers you feel in the first minute. Their order can be changed in the Builder.
Keystone: Layer 47. Load-bearing in every sense, and available as a standalone replacement.
Void Layer™: A tensioned border enclosing 2.0 mm of nothing. There are eight in the full stack. See VOID-1.
Reserve Layers: Additional numbered layers (R1 onward) that sit outside the 100. They do not count toward your Number.
Layer Audit: An annual review of your stack and Journal by a Number Integrity specialist. Free with every order.
Full Stack: A configuration of all 100 layers. Also the Number of 0.8% of certified sleepers.
Thermal Indifference: The property of maintaining the same temperature regardless of what the sleeper is doing. Achieved by the Phase-Change Gel Lattice.
Cervical Alignment Index: A measure of the angle between the second and seventh cervical vertebrae during sleep, against an ideal of 0°. Used in LOFT-3.

Every neck has a Number. We can prove it.

STRATA Sleep Sciences Institute

Dr. Halcyon Reyes-Whitlock

Dr. Ambrose Hesketh

Dr. Tobiah Fennimore

Dr. Matthias Oyelaran-Cole

Dr. Sunniva Aalto-Grieve

Dr. Marisol Uhde

Prof. Edda Morrow

Dr. Yusuf Brannigan-Toll

Dr. Lionel Achterberg

Dr. Priya Castellane

Prof. Odessa Kwan-Hartley

Method

Results

Conclusion

Method

Results

Conclusion

Method

Results

Conclusion

Clinical Study Recap

On the Existence of the Number