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Official Journal of the Italian Society of Orthopaedics and Traumatology

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

From: What type of mattress should be chosen to avoid back pain and improve sleep quality? Review of the literature

Author (year) Study design Aim Materials and methods Conclusion
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