Table 1 Summary of articles on the effects of different types and designs of mattresses, on sleep quality and pain reduction

Kovacs et al. [9]

Randomized, blinded, controlled trial

Evaluation of effects of mattress firmness on patients affected by chronic low back pain

Level of evidence: I

313 participants (155 medium-firm mattresses allocated to patients and 158 firm mattresses allocated to patients)

Patients with ≥ 3 months chronic back pain while lying in bed or on rising

VAS score used to measure level of pain symptoms

Roland Morris questionnaire administered to assess degree of disability

Although no statistically significant pain reduction was reported among groups observed, the study shows that patients with chronic low back pain can benefit from mid-firm mattresses

McCall et al. [6]

Randomized controlled trial

Comparison between a traditional and an anti-decubitus mattress, with seven different pressure areas for 2 weeks

Level of evidence: II

12 participants

Asymptomatic

Use of VAS score to measure level of pain symptoms

Actigraphy and pressure mapping

No statistically significant difference between the two mattresses in any of the measurements obtained; however, the anti-decubitus mattress reduced the number of high-pressure points

Bergholdt et al. [10]

Randomized single-blinded clinical trial

Comparison of three different types of mattresses: waterbed (Akva), memory foam mattress (Tempur), firm mattress (Futon Innovation) for 1 month

Level of evidence: II

160 participants

Symptomatic

Danish COBRA questionnaire administered to measure pain symptoms levels and activities of daily life (ADLs)

Water mattresses and foam mattresses showed best results for low back pain

Jacobson et al. [14]

Controlled trial

Comparison of sleep quality based on mattress firmness

Level of evidence: III

22 participants

Symptomatic

VAS score used to evaluate low back pain, stiffness, shoulder pain and sleep quality

Patients reported improvement of low back and shoulder pain

Jacobson et al. [5]

Controlled trial

Assessing new mid-firm mattresses systems

Level of evidence: III

59 patients

Used two questionnaires (VAS score to evaluate pain symptoms, discomfort, rachis stiffness, sleep quality; and another questionnaire related to potential stress, anxiety and irritability conditions)

Asymptomatic

Mid-firm mattresses ensure more satisfactory levels in terms of sleep, comfort and pain symptoms

Jacobson et al. [7]

Non-randomized controlled trial

Influence on sleep quality through comparison of new mattresses and personal mattress systems

Level of evidence: III

59 patients (29 male and 30 female)

Asymptomatic

Two-phases study

Evaluation of sleep quality through personal mattresses for 28 days

Evaluation of sleep quality on a new mattress system for 28 days

Use of VAS scale to assess quality of sleep, comfort and efficiency of the mattress system adopted and of pain symptoms involving low back, shoulders and rachis stiffness

New mattress systems can significantly improve sleep variables considered and quality of sleep arising from prompt replacement of mattress system components

Jacobson et al. [8]

Controlled trial

Comparison of sleep quality when using a mid-firm mattress and patient’s own mattress

Level of evidence: III

59 patients (29 male and 30 female)

Asymptomatic

Use of VAS scale to evaluate pain symptoms and sleep quality

Questionnaire formed by 32 questions related to potential stress conditions

Mid-firm mattresses are given a positive evaluation as far as reduction of low back pain and sleep quality improvement are concerned

Jacobson et al. [17]

Controlled trial

Comparison of sleep quality by using subjects’ own mattresses for 3 weeks and the prescribed mattress for 12 weeks

Level of evidence: III

27 participants

Symptomatic

Use of VAS scale to assess pain symptoms and sleep quality

Significant improvement in sleep quality and pain symptoms through new technologies-based mattress prescribed

Monsein et al. [11]

A-B-A design

Pain reduction and sleep quality effects induced by individuals’ own mattress and an air-adjustable mattress placed on the topper

Level of evidence: III

90 participants

Patients complaining of low back pain

Analysis of data linked to participants’ own mattress

Analysis of the second type of mattress for 28 days

Results evaluation conducted through Short Form (SF) 36 health survey Epworth Daytime Sleepiness Scale, and VAS

Improvement of sleep quality and low back pain following use of air mattress

Price et al. [12]

Pilot study

A-B design prospective study to evaluate sleep quality by using an air mattress system (Repose; Frontier Therapeutics Ltd, Blackwood, South Wales)

Level of evidence: III

19 patients

Patients with chronic low back pain and sleep disorders

Use of a VAS evaluation chart on sleep quality

Statistically significant results found as a consequence of air mattress system use

Bader and Engdal [16]

Randomized controlled trial

Comparison between soft and firm mattress systems and influence on sleep quality

Level of evidence: II

Ten participants

Asymptomatic

Evaluation chart used to assess pain, stress and fatigue

Use of polysomnography to evaluate sleep quality

No statistically significant result arising from comparison between two mattress systems

Lahm and Iaizzo [13]

Non-randomized controlled trial

Evaluation of cervical dorsal column orientation and its effect on sleep quality using three mattress systems with adjustable air chambers

Level of evidence: III

29 participants (15 male, 7 female)

Asymptomatic

Assessment of EMG activity, heart rate, blood pressure, subjective comfort levels and data on column alignment on different pressure degrees of the mattress system

Questionnaire related to subjective opinions on sleep quality

Although mattress inflation pressure induced significant changes on spinal alignment, these had limited physiological consequences. However, such data provide essential information to evaluate similar associations in a symptomatic population (acute/chronic low back pain and cervical pain)

López-Torres et al. [21]

Non-randomized controlled trial

Evaluation of sleep quality taking into consideration four types of mattresses: spring mattress, latex, polyurethane, two-layer firmness system

Level of evidence: III

75 participants

Asymptomatic

Questionnaire regarding structural and morphological qualities of the mattress (firmness and softness)

Results of comparative analysis were correlated to differences of objective properties such as pressure distribution and objective firmness. Consequently, results on morphological and structural characteristics of mattress systems analysed (firmness and softness) were directly proportional to comfort reported by patients analysed

Raymann et al. [19]

Experimental

Evaluation of skin temperature during sleep

Level of evidence: VI

24 participants (8 young adults, 8 old asymptomatic subjects and 8 symptomatic subjects)

Asymptomatic patients and patients with insomnia

Proximal and distal skin temperature manipulation via thermal suit between 12:00 and 6:00 AM. Cycling between 31.7 °C ± 0.1 °C in “cool” and 34.5 °C ± 0.1 °C in “warm”. Total length of test was 4 days. Day 1 was spent sleeping at home. Day 2 was spent sleeping in the laboratory. Day 3 was spent sleeping at home. Day 4 was spent sleeping in the laboratory. Subjects wore the thermal suit on days 2 and 4

Temperature check in bed through soft manipulation might have a strong clinical impact on sleep alterations, especially in the elderly who are not able to effectively respond to temperature variations

Tonetti et al. [1]

Actigraphic study

Evaluation of sleep quality comparing the use of a spring mattress and the Myform system for 2 weeks

Level of evidence: VI

28 participants (14 male, 14 female)

Asymptomatic

Mini Sleep Questionnaire and Hassles Scale adoption

Evaluation of sleep parameters: sleep efficiency, insomnia latency and motor activity

Sleep quality improves thanks to Myform, but this result does not seem statistically significant

McCall et al. [6]

Controlled trial

Evaluation of sleep quality using an intelligent mattress system. Comparison between standard and dynamic configuration

Level of evidence: III

11 participants

Asymptomatic

Use of polysomnography to assess sleep

Karolinska Sleepiness Scale, Profile of Mood State

Subjective evaluation regarding sleep quality

Active control system with dynamic configuration resulted in increased sleep quality. Participants perceived fewer awakenings and awakenings were shorter with the active control system with dynamic configuration

Verhaert et al. [27]

Non-randomized controlled trial

Evaluation of an ergonomic mattress system and its effect on sleep

Level of evidence: III

17 participants

Asymptomatic

Use of different questionnaires [VAS (0–20),Karolinska Sleepiness Scale, Cox’s Stress/Arousal, Adjective Check List, the fatigue scale of Profile of Mood]

Polysomnography to objectively evaluate sleep quality

Video-recording aids

The effect of bed design on sleep cannot be fully evaluated just comparing two sleep systems. A relaxed sleep system has a negative effect on sleep quality for people who spend most of the time in a lateral sleep position. Individuals who sleep in lateral position also spent a significantly shorter time in REM compared with the standard condition

Park et al. [18]

Multicenter controlled trial

Evaluation of the relations between the characteristic of mattress, anthropometric features, body pressure distribution and spinal curvature and to examine overall relations between the comfort and features of mattress. Six materials, i.e. three kinds of cotton, felt, sponge and elastic cotton, were used as pad materials. Springs were 3-pitch, 4-pitch or 5-pitch

Level of evidence: III

18 participants (9 male, 9 female)

Asymptomatic

3D measurement of vertebrae column at C7, T1, T3, TT, Tg, T11, L2, L5/S1 and of sacrum and coccyx prominences

Pressure measurement at hips and shoulders through sensors

The subject fills out six evaluation charts that uses seven-point scales (divided into two sections) about the degree of satisfaction and physical features

The best mattress was the mattress in which the spinal curvature in lying position was most similar to that in standing. The firmness had to be extended to increase patient comfort

Price et al. [12]

Pilot study

Prospective study AB design about the use of an air flotation mattress for 4 weeks overlay in patients with chronic pain

Level of evidence: III

19 participants

Patients with chronic pain symptoms and sleep alterations

Evaluation about self-reported changes in sleep quantity and frequency of sleep disturbance, and about self-reported changes in pain and use of analgesia

This study reported statistically significant results about improvement in sleep and pain after 4 weeks with the use of a new (low-pressure inflatable) overlay mattress

Shen et al. [36]

Randomized control trial

Comparing 18 different types of spring mattresses (5 different spring cores, 14 different top comfort combination layers)

Level of evidence: II

Eight participants

Asymptomatic

Polysomnography [electrocardiogram, electrooculogram, electroencephalogram, electromyography (EMG)], actigraphy (sleep/wake behaviour), body movements

Questionnaire about level of fatigue of body parts before sleep, discomfort, sleepiness and pain after sleep

Morphological and structural features of the mattress influence sleep quality

Sleep quality depends on postural characteristics

Subjective opinion on mattress system characteristics

Lee et al. [31]

Randomized control trial

Study of the effects of the type of mattress on sleep quality by measuring the temperature of the skin, using a subjective mattress evaluation system and through the use of a polysomnogram

Level of evidence: II

16 participants (age range 20–30 years)

Asymptomatic

Personal recordings about sleep quality

Polysomnography data, skin temperature

To ensure efficient sleep quality, a mattress must guarantee the best support for the spine, maintain constant body temperature and reduce body movements during sleep

DeVocht et al. [4]

Controlled trial

Objective, biomechanical comparison of four “top of the line” mattresses from four different manufacturers (mattress A, Perfect Contour Extraordinaire Dorchester by King Koil; mattress B, Beautyrest Calibri Firm by Simmons; mattress C, Posturepedic Afton Plush by Sealy; mattress D, Perfect Sleeper Southdale by Serta)

Level of evidence: III

18 patients (all male)

Asymptomatic

Two different measurements (pressure distribution during the supine position and evaluation of the degree of spinal distortion induced when in the side posture position)

The pelvic region had higher pressure values when compared with the thoracic region. The least amount of pressure was seen in mattress A (Perfect Contour Extraordinare Dorchester by King Koil), and the highest pressure was seen in mattress D (Perfect Sleeper Southdale by Serta). Mattress D also demonstrated the lowest level of spinal distortion

Leilnahari et al. [26]

Controlled trial

Evaluation of pressure exerted on the column based on the degree of mattress firmness: soft (polyurethane foam), firm, and custom-made mattresses

Level of evidence: III

25 participants (all male)

Asymptomatic

Comparison between pressure exerted on the column (through sensors placed on spinal processes) both in lateral and routine position

The results showed a significant difference in the π-P8 angles between soft and custom-made and soft and firm mattresses at the p = 0.001 level and between firm and soft mattresses at the p = 0.05 level

A custom-made mattress can be effective for heavier patients. The stiffness of the mattress influences the forces exerted on the spine

Normand et al. [30]

Quasi-experimental

Evaluation of six different conditions using three types of surfaces (no mattress, 8 cm of foam, 14 cm latex mattress of medium density)

Level of evidence: III

Ten participants

Asymptomatic

Assessment of pressure distribution on the thorax, pelvic and low back areas (Tekscan pressure sensor) in supine position for 30 s

Use of a low back support led to a homogeneous pressure on the thorax, low back and pelvis in supine position

Chen et al. [22]

Randomized cross-over, single-blinded controlled trial

To investigate the influence of mattress firmness on body contact pressure and sleep quality

Level of evidence: II

16 healthy males (aged 20–45 years)

Sleeping posture: supine lateral

Mattress characteristics:

(1) Plank springs

(2) With supporting layer and pillow top made of palm fibre

(3) 3D structure made of foam rubber and plant fibre, with supporting layer, intermediate layer finely fitting the shape of the human body, and pillow top. (4) Independent springs

Methods: (1) ABW body pressure measurement system; (2) ALICELE PSG polysomnography; (3) questionnaire, yes/no questions on hardness, comfortability, and difficulty to fall asleep

Measurement:

(1) Body-mattress contact pressure

(2) Sleep quality/polysomnography

(3) Subjective feedback

The results reveal that a mattress with an intermediate level of contact pressure led to better sleep quality

Denninger et al. [15]

Design process, validation of simulation (deviation)

Measurement of body dimensions, body mass distribution and force compression curve

Level of evidence: VI

Sleeping posture: lateral

Mattress characteristics: custom-made mattress consisted of rows and columns of PU foam (extra-firm Q41) cubes with hollow ellipsoidal cavities. Cube dimensions were customized according to spinal curvature and body weight portion

Methods:

(1) POWERSHOT A610 camera; (2) custom-made apparatus with load cells; (3) ANSYS, finite element method; (4) Optotrak 3020 optical measurement system

Measurement:

(1) Body dimensions

(2) Body mass distribution

(3) Force–compression curve of foam cubes loaded with body volume slice

A design process comprising a look-up table of human–mattress interaction predicted by simulation was established. The design of a customized mattress with different cube cavity dimensions could be defined together with the input of body properties. Validation showed a load distribution within a 10% average deviation from the expected distribution; spine alignment was within a distance of ± 3% shoulder width from the expected spine curvature

Deun et al. [37]

Repeated measures, non-randomized controlled trial

Investigation of sleep quality induced by an active-control bedding system that autonomously alters stiffness distribution according to the estimated spinal alignment, as compared with the inactive mode of this system

Level of evidence: III

Three subjects (one female, two male) with non-specified age

Sleeping posture: Lateral

Mattress characteristics:

Custom-made mattress consisted of rows and columns of PU foam (extra-firm Q41) cubes with hollow ellipsoidal cavities. Cube dimensions were customized according to spinal curvature and body weight portion

Eleven healthy subjects (five female, six male) aged 20–28 years, mean age 21.2 ± 3.2 years

Sleeping posture: No control, postures were detected and estimated

Mattress characteristics:

Dynasleep, mattress equipped with indentation sensors and adaptive actuator spring pockets. (1) Actuator inactive and (2) actuator active induced different stiffness in eight zones to optimize spinal curvature based on the results of indentation measurements

Measurements: (1) body surface contour; (2) sleep quality/polysomnography; (3) spinal curvature; (4) subjective feedback

Methods:

(1) IKÉLO optical measurement system; (2) dream system, polysomnograph; (3) indentation sensors embedded in Dynasleep mattress (spinal curvature was simulated and estimated by indentation using a human model personalized based on the results of body contour measurements); (4) questionnaires: Karolinska sleepiness scale, profile of mood state, stress/arousal adjective checklist, activation/deactivation adjective checklist

When active control mode was used, sleep quality was significantly improved, as revealed by polysomnographic analysis and subjective feedback

Esquirol Caussa et al. [28]

Recommendation model, validation of somatotype model (correlation)

Design and validation of an automatic multimodal somatotype determination model to automatically recommend mattress–pillow topper design combinations

Level of evidence: VI

First pilot test: six subjects, age/gender not specified; Second pilot test: 50 subjects (28 female, 22 male) aged 18–93 years, mean 34.2 years; final study: 151 subjects (60 female, 91 male) aged 4–94 years, mean 34.43 years; re-analysis study: 117 subjects (75 female, 42 male), aged 4–93 years, mean 33.82 years

Sleeping posture: Supine

Mattress characteristics:

(1) Soft, density 2.75 kPa*; (2) neutral/soft, density 3.0 kPa; (3) neutral, density 3.3 kPa; (4) neutral/hard, density 3.8 kPa; (5) hard, density 4.4 kPa. Three types of toppers (DORMITY): (1) soft, density 1.1 kPa; (2) medium, density 1.6 kPa; (3) hard, density 2.1 kPa. Three types of pillows of different densities (45 combinations)

Measurements:

(1) Body dimensions; (2) body–mattress contact pressure

Methods:

(1) Kinect camera and tape; (2) surface with integrated pressure capacitive sensors

Validation of somatotype models demonstrated a high correlation index compared with real data: more than 85% in height and body circumferences; 89.9% in weight; 80.4% in body mass index; and more than 70% in morphotype categorization

Lee et al. [24]

Mixed factorial design (gender, body regions, duration), non-randomized controlled trial

Analysis of body pressure and perceived level of pain for different genders, body regions and durations of supine lying

Level of evidence: III

Ten healthy subjects (five female, 5 male), age mean 29.1 ± 3.2 years

Sleeping posture: Supine

Mattress characteristics:

Subjects’ existing mattress

Measurement:

(1) Body–mattress contact pressure; (2) subjective feedback

Methods

(1) Body pressure measurement system; (2) questionnaires: pain score using visual analogue scale, faces pain rating scale, Iowa pain thermometer

Head regions experienced significantly higher pain scores and pressure intensities; lower back was not too high in pressure intensity but featured the second-highest pain score; the back and pelvic girdle showed a significant difference between males and females on the pain score; pain appeared in all body regions after 10 min and progressed as time increased

Lee et al. [23]

Repeated measurements, non-randomized controlled trial

Comparison of body pressure and perceived level of pain between the floor and mattress for different durations of supine lying

Level of evidence: III

Ten healthy subjects (five female, five male), age mean 29.1 ± 3.2 years

Sleeping posture: Supine

Mattress characteristics:

(1) Floor; (2) mattress

Measurement: (1) Body–mattress contact pressure; (2) subjective feedback

Methods:

(1) Body pressure measurement system; (2) questionnaires: pain score using visual analogue scale, face pain rating scale, Iowa pain thermometer

Head regions featured a significantly higher-pressure intensity; the pain scores of all body regions except for legs were significantly higher for the floor condition; the pain score of the floor condition significantly increased at 1 min compared with those of the mattress group

Leilnahari et al. [26]

Design process, repeated measurements, non-randomized controlled trial

Design of a customized mattress with different zonal elasticity that can achieve optimal spinal alignment; comparison of spinal alignment achieved by firm, soft and custom mattresses

Level of evidence: III

25 male students

Sleeping posture: lateral

Mattress characteristics:

Spinal deformities: lateral. (1) Soft mattress (polyurethane foam and a layer of memory foam; (2) firm mattress; (3) custom-made mattress with different regional stiffness based on neutral spine alignment predicted by the musculoskeletal model. The mattress was made of a combination of PU and spiral pressure springs with different wire diameters

Measurements: spinal curvature

Methods:

(1a) DCR-TRV356E cameras; (1b) BRG.LIFEMOD2007, musculoskeletal modelling (spinal curvature was simulated and estimated by modelling and validated by captured images)

The customized mattress with different zonal elasticity afforded better spinal alignment (least π-P8), followed by firm and soft mattresses

López-Torres et al. [21]

Non-randomized controlled trial, correlation

Comparison of perceived firmness, usability and comfort between young and elderly people; investigation of the correlation between subjective ratings and results of objective measurements (pressure distribution and objective firmness)

Level of evidence: III

19 young subjects (9 female, 10 male), age mean 28 ± 3 years (female), 26 ± 3 years (male); 56 elderly subjects (34 female, 22 male), age mean 67 ± 5 years (female); 70 ± 6 years (male)

Sleeping posture:

Three-step testing procedure: (1) seated position; (2) supine; (3) roll onto one side. Four mattresses were selected from 17 samples to cover the full range of firmness

Mattress type:

Four mattresses were selected from 17 samples to cover the full range of firmness

Measurement:

(1) Mannequin-mattress contact pressure; (2) subjective feedback

Methods:

(1) PLIANCE 19 P body pressure measurement system; (2) questionnaire: perceived firmness with hands, buttocks, in supine/lateral posture; difficulties in rolling over and getting up; four-point grading in comparing overall comfort

No perception differences between the young and the elderly were found. Significant correlations were found between increments in objective firmness and perceived firmness (positive); increments in average pressure and perceived firmness (positive); increments in objective firmness and average pressure were associated with increments in overall comfort and reductions in rolling difficulty

Low et al. [25]

Randomized cross-over, single-blinded controlled trial

Comparison of the body contact pressure profile of different mattresses in three different postures

Level of evidence: II

20 young healthy subjects (10 female, 10 male), age: not specified

Sleeping posture:

Supine lateral prone

Mattress characteristics:

(1) Delight, latex foam mattress; (2) Masterfoam 1000, high-density PU foam mattress

Measurements: body–mattress contact pressure

Methods:

(1) TEKSCAN 5400 N pressure mapping sensor

Compared with the case of a PU mattress, reduced peak pressure and a more even pressure distribution were observed for a latex mattress

Palmero et al. [29]

Recommendation model, validation for morphotype categorization (confusion matrix, correlation)

Development and validation of a somatotype determination model based on 3D RGBdepth imaging (Kinect) and automatic landmark points extraction; establishment of a recommendation model for mattress–pillow topper design combinations based on somatotype model and pressure analysis

Level of evidence: III

200 subjects (128 female, 72 male) aged 4–93 years, mean 33.82 ± 23.02 years

Sleeping posture: supine

Mattress characteristics: intermediate-density mattress

Measurements: (1) body surface contour; (2) body–mattress contact pressure

Methods: (1) Kinect camera; (2) in-house built capacitive pressure-sensitive mattress sensor

The system was capable of accurate categorization and achieved high correlation results with respect to manual measurement

Park et al. [31]

Design process, repeated measurements, non-randomized controlled trial

Development of an adjustable bed that regulates the height of eight mattress sectors and allows self-adjustment: comparison of adjustable bed and flatbed comfort ratings

Level of evidence: III

64 healthy subjects (35 female, 29 male) aged 25–50 years

Sleeping posture: supine lateral prone

Mattress characteristics: adjustable bed system with eight sectors that allowed the sector height to be controlled by subjects to achieve the most comfortable feeling; (1) without adjustment, (2) with adjustment

Measurement: (1) body–mattress contact pressure; (2) subjective feedback

Methods:

(1) Self-assembled force-sensing resistor matrix; (2) questionnaire, five-point scale of comfortability in nine body regions (neck, shoulder, back, elbows, lumbar, hand/wrist, hip/thigh, knee, ankle)

Subjects preferred height adjustment in W-shape in supine and lateral postures, and in U-shape in lateral prone postures

The adjusted height was significantly correlated with (a) the subjective rating and (b) the ratio of bed sector regional pressure and the total bed pressure

Verhaert et al. [27]

Repeated measurements, non-randomized controlled trial

Investigation of the effect of an active-control bedding system autonomously altering stiffness distribution according to the estimated spinal alignment and comparison to a sagging bedding system

Level of evidence: III

17 healthy subjects (8 female, 9 male), age mean 24.3 ± 7.1 years

Sleeping posture: no control, biomechanical measurement on lateral posture only

Mattress characteristics: Dynasleep, mattress equipped with indentation sensors and adaptive actuator spring pockets. (1) Actuator active, induced different stiffness in eight zones to optimize spinal curvature based on the results of indentation measurements; (2) manually adjusted actuator to simulate a sagging support (high stiffness at shoulder zone, low stiffness at the waist and hip zones)

Measurement: (1) body dimensions; (2) body surface contour; (3) spinal curvature

Methods: (1) calliper and tape; (2) IKÉLO optical measurement system; (3) indentation sensors embedded in Dynasleep mattress (spinal curvature was simulated and estimated by indentation using a human model personalized based on the results of body contour measurements)

The sagging sleep system negatively affected sleep quality in prone and lateral postures; the relationship between mattress design and sleep quality was affected by anthropometry and posture

Verhaert et al. [16]

Instrument design, validation (correlation)

Development of an estimation method for spinal alignment by integration of a personalized human model and mattress indentation measurements

Level of evidence: III

65 subjects (33 female, 32 male), age mean 27.3 ± 11.5 years. Validation: subgroup of 20 subjects (8 female, 12 male), age mean 22.9 ± 3.8 years

Sleeping posture:

Supine lateral prone

Mattress characteristics:

Dynasleep, mattress equipped with indentation sensors and adaptive actuator spring pockets. (1) Actuator active, induced different stiffness in eight zones according to anthropometric measurements and BMI; (2) manually adjusted actuator to simulate a sagging support

Measurement:

(1) Body dimensions; (2) body surface contour; (3) spinal curvature

Methods:

(1) Calliper and tape; (2) IKÉLO optical measurement system; (3) indentation sensors embedded in Dynasleep mattress (spinal curvature was simulated and estimated by indentation using a human model personalized based on the results of body contour measurements)

Good intraclass correlation (0.73–0.88) between estimated and measured angular spinal deformation was observed

Verhaert et al. [38]

Instrument design, validation (deviation), recommendation model

Estimation of spinal shape using a personalized anthropometric model and load–deflection characteristics of the mattress and bed base; presentation of a method to identify mattress bed base combinations with superior support properties

Level of evidence: III

18 subjects (9 female,9 male), age mean 28.5 ± 4.7 years

Sleeping posture:

Lateral three types of bed base: (1) homogeneous box-spring; (2) multi-zone slatted base; (3) multi-zone mesh base

Mattress characteristics:

(1) Multi-zone pocket spring mattress; (2) multi-zone latex mattress; (3) homogeneous PU foam mattress (nine combinations)

Measurement:

(1) Body surface contour; (2) body surface contour (for validation); (3) spinal curvature

Instruments:

(1) IKÉLO optical measurement system; (2) zSnapper 3D scanner; (3) spinal curvature was simulated and estimated based on the mass distribution of body portions and the human model personalized by body surface measurements and validated by 3D scanning

Estimation showed good correspondence (85%) in comparison with the validated spine shape in terms of score ranking

Verhaert et al. [39]

Mattress design process, randomized crossover single-blinded controlled trial

Presentation of an active control mattress system that can: (1) detect body movement and recognize sleep posture; (2) estimate the shape of the spine by combining indentation with human models; (3) based on indentation measurement and feedback, control the mattress system to achieve optimal spinal alignment by customizing regional mattress stiffness. Performance comparison of the active and non-active modes of the active-control mattress

Level of evidence: III

18 subjects (8 female, 10 male), age mean 31.3 ± 14.3 years. Field study: 12 subjects (6 female, 6 male), age mean 38.7 ± 23.4 years

Sleeping posture:

No control, postures were detected and estimated in system configuration; six sets of postures in a field study (supine, left/right lateral, prone, intermediate left/right)

Mattress characteristics:

Dynasleep mattress equipped with indentation sensors and adaptive actuator spring pockets

Measurements:

Spinal curvature

Methods: indentation sensors embedded in Dynasleep mattress (spinal curvature was estimated using indentation data and a personalized human model)

The use of the active-control mattress system significantly improved the perceived sleep quality

Wu et al. [40]

Instrument design, repeated measurements

Development of a mattress evaluation method based on body pressure distribution and comparison of back surface and spinal alignment between supine lying and upright standing through finite element simulation. Comparison of the outcomes obtained for a palm fibre mattress and a bilayer latex/palm fibre mattress

Level of evidence: III

17 healthy subjects (4 female, 13 male), age mean 34.9 ± 9.7 years

Sleeping posture:

Supine

Mattress type:

1. Palm fibre; (2) bilayer, upper layer: latex, lower layer: palm fibre, Young’s modulus E = 46.73 ± 5.72 kPa. Latex, hyper-elastic Ogden’s parameter, m = 1.28 ± 0.13 kPa, a = 4.175 ± 0.885, b = 0.314 ± 0.048

Measurements:

(1) Back surface contour; (2) spinal alignment/mattress indentation; (3) body–mattress contact pressure

Methods:

(1) 3D body scanning system; (2) ANSYS finite element model; (3) Tactilus body pressure measurement system

A novel parameter was proposed by comparing the back surface contours of supine lying and natural standing postures via similarity analysis. The bilayer latex/palm fibre mattress produced a back surface contour close to that of upright standing, which indicated a preferable selection

Yoshida et al. [32]

Correlation (simulation versus subjective rating)

Investigation of the relationship between the outcome of computer simulation (finite element analysis) and subjective ratings on preference and comfort

Level of evidence: III

14 male college students aged 21–24 years. Finite element model: three subjects were picked from the pool to form the best body dimension coverage

Sleeping posture:

Supine

Mattress type:

Four types of pocket coil mattress with (1) E = 14.0 kPa; (2) E = 11.4 kPa; (3) E = 9.6 kPa; (4) E = 6.0 kPa

Measurements: (1) internal stress, head and chest displacement; (2) subjective feedback

Instruments:

(1) ANSYS finite element model; (2) questionnaire, seven-grade scale on the feeling of firmness, mattress preference, firmness preference, sinking preference, comfort for different regions of the body

The subjective ratings corresponded to the prediction outcome, including the von Mises stress of the cervical vertebral region and the sinking displacement of the neck region

Zhong et al. [33]

Instrument design, validation (error analysis), mattress design process

Estimation of spinal curvature with mattress indentation

Determination of an optimal mattress zonal stiffness

Level of evidence: III

Nine females classified into three groups (n = 3) based on BMI

Sleeping posture:

Supine

Mattress type:

A total of 14 mattresses formed by the different combination of regional stiffness in five zones using six types of spring stiffness. The mattress consisted of a superficial layer of PU foam and a core layer composed of rows of pocketed springs

Measurements:

Spinal curvature

Methods:

(1) Custom-made indentation measuring bar embedded in the mattress (spinal curvature was estimated by fitting a curve on the indentation points)

The overall mean absolute error and mean relative error between the estimation and experimental measurements equalled 3.4 mm (SD 2.7) and 9.27%, respectively. cervicothoracic (CTh), thoracolumbar (ThL) and lumbosacral (LS) generally increased with lower back and hip zone stiffening; the upper body became more levelled with stiffened hip zones and more inclined with stiffened upper back zones