A mattress is a large pad for supporting the reclining body, used as or on a bed. Mattresses may consist of a quilted or similarly fastened case, usually of heavy cloth, that contains hair, straw, cotton, foam rubber, etc.; a framework of metal springs; or they may be inflatable.
The word mattress derives from the Arabic matrah, which means "something thrown down" or "place where something is thrown down" and hence "mat, cushion". During the Crusades Europeans adopted the Arabic method of sleeping on cushions on the floor, and the word materas eventually descended into Middle English through the Romance languages.
Mattresses are usually placed on top of a bed base which may be solid, as in the case of a platform bed, or elastic, e.g. with an upholstered wood and wire box spring or a slatted foundation. Popular in Europe, a divan incorporates both mattress and foundation in a single upholstered, footed unit. Divans have at least one innerspring layer as well as cushioning materials. They may be supplied with a secondary mattress and/or a removable "topper."
Early mattresses contained a variety of natural materials including straw, feathers or horse hair. In the first half of the 20th century, a typical mattress sold in North America had an innerspring core and cotton batting or fiberfill. Modern mattresses usually contain either an inner spring core or materials such as latex, viscoelastic or other flexible polyurethane foams. Other fill components include insulator pads over the coils that prevent the bed's upholstery layers from cupping down into the innerspring, as well as polyester fiberfill in the bed's top upholstery layers. Mattresses may also be filled with air or water, or a variety of natural fibers, such as in futons. In Southeast Asia, bedding is made with kapok. In 1900 English-born engineer, James Marshall introduced the first individually wrapped pocketed spring coil mattress now commonly known as marshall coils and founded Marshall Mattress, a company that bears his name and is still in operation in Toronto, Canada. He allowed VI-Spring patent rights in England where they were known as Marshall Mattress of England until the 1930s.
In North America the typical mattress sold today is an innerspring; however there is increasing interest in all-foam beds and so-called hybrid beds, which include both an innerspring and high-end foams such as visco-elastic or latex in the comfort layers. In Europe, polyurethane foam cores and latex cores have long been popular and make up a much larger proportion of the mattresses sold. In South Asia, coir is a common mattress material.
- 1 History
- 2 Mattress dimensions
- 3 Construction
- 4 Types of mattress
- 4.1 Innerspring
- 4.2 Foam mattress
- 4.3 Bladder mattresses
- 5 Quality
- 6 Lifespan
- 7 Maintenance and care
- 8 See also
- 9 References
|This section needs additional citations for verification. (February 2010)|
- Neolithic period: The mattress and bed are invented. Beds are raised off the ground to avoid drafts, dirt, and pests. The first mattress probably consisted of a pile of leaves, grass, or possibly straw, with animal skins over it.
- 3600 B.C.: Beds made of goatskins filled with water are used in Persia.
- 3400 B.C.: Egyptians sleep on palm boughs heaped in the corners of their homes.
- 200 B.C.: Mattresses in Ancient Rome consist of bags of cloth stuffed with reeds, hay, or wool; the wealthy use feather stuffing.
- 15th century: During the Renaissance, mattresses are made of pea shucks, straw, or sometimes feathers, stuffed into coarse ticks, and covered with velvets and brocades.
- 16th and 17th centuries: Mattresses are stuffed with straw or down and placed atop a bed consisting of a timber frame with support latticeworks of rope or leather.
- Early 18th century: Mattresses are stuffed with cotton or wool.
- Mid 18th century: Mattress covers begin to be made of quality linen or cotton. The mattress cane box is shaped or bordered, and fillings include natural fibers such as coconut fibre, cotton, wool, and horsehair. The mattress is tufted or buttoned to attach the stuffing to the cover and the edges are stitched.
- Late 19th century: The box-spring is invented to distribute weight and act as a shock absorber, thereby lengthening the life of an innerspring mattress.
- 1926: Dunlop introduced a technology to produce vulcanized rubber latex foam. Similar foams still are used in latex mattresses and pillows (hence the name Dunlopillo). Initially it was only sold to British royalty.
- 1930s: Innerspring mattresses and upholstered foundations become widely used, and artificial fillers become common. Encased coil spring mattresses, which consist of individual springs sewn into linked fabric bags, are introduced.
- 1940s: Air mattresses constructed of vulcanized rubber-coated fabric are introduced.
- 1960s: The modern waterbed is introduced and gains its first widespread use. Adjustable beds gain popularity. The California king size bed is introduced.
- 1970s: NASA invents material that later becomes known as memory foam.
- 1970s: A more advanced technology to produce synthetic foam rubber mattresses and pillows enabled factories to mass-market latex foam and reduce the consumption of natural rubber latex.
- 1992: Tempur-Pedic introduces a mattress made from memory foam.
- 1992: Fibrelux introduces a mattress made from rubberized coir.
- 2000: Simmons Bedding Co. invents the "no-flip" mattress by removing the padding on one side of the mattress, a construction style that has since been adopted by most North American mattress manufacturers.
Mattresses thicknesses range from four to eighteen inches (10 to 46 cm).
|Crib / toddler||27 1⁄4 in × 51 5⁄8 in (69 cm × 131 cm)||27 1⁄2 in × 55 in (70 cm × 140 cm)
|Cot/mini single||30 in × 70 in (76 cm × 178 cm)
(this size is not common in the US)
|30 in × 69 in (76 cm × 175 cm)
|Small single||30 in × 75 in (76 cm × 191 cm)
(small single is used to mean several different sizes)
|Modern cot||30 in × 74 in (76 cm × 188 cm)|
|Single/twin||39 in × 75 in (99 cm × 191 cm)
|36 in × 75 in (91 cm × 191 cm)||90 cm × 190 cm (35 in × 75 in)||107 cm × 198 cm (42 in × 78 in)|
|Single/twin XL||39 in × 80 in (99 cm × 203 cm)||42 in × 75 in (107 cm × 191 cm)|
|Double/full||54 in × 75 in (137 cm × 191 cm)||48 in × 75 in (122 cm × 191 cm)
|140 cm × 190 cm (55 in × 75 in)||122 cm × 198 cm (48 in × 78 in)|
|Double/full XL||53 in × 80 in (135 cm × 203 cm)||54 in × 75 in (137 cm × 191 cm)
(not commonly found, typically for antique/heirloom beds)
|48.0 in × 73.0 in–75.0 in (122 cm × 185 cm–191 cm)|
|Queen||60 in × 80 in (152 cm × 203 cm)||160 cm × 200 cm (63 in × 79 in)||153 cm × 198 cm (60 in × 78 in)|
(primarily a wood-framed water bed size, becoming obsolete)
|60 in × 84 in (152 cm × 213 cm)|
|King (Eastern king)||76 in × 79 in (193 cm × 201 cm)||60 in × 78 in (152 cm × 198 cm)
|180 cm × 200 cm (71 in × 79 in)||183 cm × 198 cm (72 in × 78 in)|
|California king waterbed insert||70 in × 82 in (178 cm × 208 cm)|
|California king||72 in × 84 in (183 cm × 213 cm)|
|Super king||72 in × 78 in (183 cm × 198 cm)|
A conventional mattress consists of two primary sections – a core or "support layer" and the upholstery or "comfort layer" – wrapped in a thick fabric called the ticking.
Upholstery layers cover the mattress and provide cushioning and comfort. The upholstery layer consists of three parts: the insulator, the middle upholstery, and the quilt.
Types of mattress
A common innerspring mattress consists of three components: the spring core, the foundation, and the upholstery layers.
The core of the mattress supports the sleeper’s body. Modern spring mattress cores, often called "innersprings," are made up of steel coil springs, or "coils."
The gauge of the coils is another factor which determines firmness and support. Coils are measured in quarter increments. The lower the number, the thicker the spring. In general, higher-quality mattress coils have a 14-gauge (1.63 mm) diameter. Coils of 14 to 15.5-gauge (1.63 to 1.37 mm) give more easily under pressure, while a 12.5-gauge (1.94 mm) coil, the thickest typically available, feels quite firm.
Connections between the coils help the mattress retain its shape. Most coils are connected by interconnecting wires; encased coils are not connected, but the fabric encasement helps preserve the mattress shape.
There are four types of mattress coils:
- Bonnell coils are the oldest and most common. First adapted from buggy seat springs of the 19th century, they are still prevalent in mid-priced mattresses. Bonnell springs are a knotted, round-top, hourglass-shaped steel wire coil. When laced together with cross wire helicals, these coils form the simplest innerspring unit, also referred to as a Bonnell unit.
- Offset coils are an hourglass type coil on which portions of the top and bottom convolutions have been flattened. In assembling the innerspring unit, these flat segments of wire are hinged together with helical wires. The hinging effect of the unit is designed to conform to body shape. LFK coils are an unknotted offset coil with a cylindrical or columnar shape.
- Continuous coils (the Leggett & Platt brand name is "Mira-coil") is an innerspring configuration in which the rows of coils are formed from a single piece of wire. They work in a hinging effect similar to that of offset coils.
- Marshall coils, also known as wrapped or encased coils or pocket springs, are thin-gauge, barrel-shaped, knotless coils individually encased in fabric pockets—normally a fabric from man-made, nonwoven fiber. Some manufacturers precompress these coils, which makes the mattress firmer and allows for motion separation between the sides of the bed. As the springs are not wired together, they work more or less independently: the weight on one spring does not affect its neighbours. More than half the consumers who participated in a survey had chosen to buy pocket spring mattresses.
There are three main types of foundation.
- A traditional box spring consists of a rigid frame containing extra heavy duty springs. This foundation is often paired with an innerspring mattress, as it extends the life of the spring unit at the mattress's core. All-foam mattresses are often paired with platform-style bases.
- An all-wood foundation usually has seven or eight support slats disposed below paperboard or beaverboard. This foundation, variously called a "no-flex," "low-flex" or zero-deflection unit, as well as an "ortho box," provides support similar to a platform foundation. All-wood foundations have become increasingly prevalent as U.S. mattress makers shifted to super-thick, one-sided mattresses.
- A grid-top foundation is a combination of steel and wood.
- Typically the measurements of a foundation will be about 1-2" shorter than the measurement of a mattress.
Upholstery layers cover the mattress and provide cushioning and comfort. Some manufacturers call the mattress core the "support layer" and the upholstery layer the "comfort layer." The upholstery layer consists of three parts: the insulator, the middle upholstery, and the quilt.
The insulator separates the mattress core from the middle upholstery. It is usually made of fibre or mesh and is intended to keep the middle upholstery in place.
The middle upholstery comprises all the material between the insulator and the quilt. It is usually made from materials which are intended to provide comfort to the sleeper, including flexible polyurethane foam [which includes convoluted "egg-crate" foam], visco-elastic foam, latex foam, felt, polyester fiber, cotton fiber, wool fiber and nonwoven fiber pads. In Europe and North America, mattress makers have begun incorporating gel-infused foams, soft-solid gels layered over foam, and poured gels in the top comfort layer of the bed.
The quilt is the top layer of the mattress. Made of light foam or fibres stitched to the underside of the ticking, it provides a soft surface texture to the mattress and can be found in varying degrees of firmness.
The protective fabric cover which encases the mattress and foundation is called ticking. It is usually designed to coordinate with the foundation border fabric and comes in a wide variety of colors and styles. Mattress fabrics can be knits, damask or printed wovens, or inexpensive nonwovens. During the past decade, along with the rise in popularity of all-foam beds, stretchy knit ticking on the bed's top panel has become a standard look on both innerspring and foam beds. Most ticking is made with polyester yarns. More expensive mattress fabrics may contain a combination of polyester with rayon, cotton, silk, wool or other natural yarns.
Until the early 2000s, beds were normally upholstered with a single fabric. This was usually a damask ticking or, for inexpensive bedsets, a nonwoven fabric covering all surfaces of the mattress and foundation. Today's bedsets are covered with up to six different fabrics: A better quality circular knit or woven damask on the top panel—the bed's sleeping surface; a matching or contrasting [usually woven] fabric on the border of the mattress; a matching or contrasting [usually woven] fabric on the foundation side panels; a 'non-skid' woven or non-woven fabric on the surface of the foundation and reverse side of the mattress; and a nonwoven dust cover on the under side of the foundation. Some North American mattress producers are beginning to use furniture upholstery fabrics on the bed's borders giving beds a more European, home furnishings look.
All-foam mattresses use different weights and densities of petrochemical-based flexible polyurethane foams when creating the mattress. and visco-elastic foams or memory foam, and latex rubber foams. A number of mattress manufacturers have incorporated polyurethane and visco-elastic foams with a portion of plant-based content.
Latex foam in mattresses is generally a blend of the latex of the Hevea brasiliensis tree and synthetic latex, which is derived from petrochemicals and other substances and fillers. There are, however, natural latex mattresses that leave out polyurethane-based chemicals. Latex foam is produced using either the Talalay or the Dunlop process. Each provides a different feel. Dunlop is generally a firmer foam, Talalay is softer. While the Dunlop process produces a denser foam, the Talalay process produces a lighter one that has more air in it. If you were to weigh each as latex cores, the Dunlop foam would be heavier because it has more latex in it. Talalay is more expensive as its production is more resource intensive. Natural latex foam has a higher latex content than synthetic latex, however, "100% natural latex foam" is misleading.
Memory foam mattresses use conforming visco-elastic foam over firmer polyurethane base foam. Some innerspring mattresses have memory foam in their upholstery layer. Different feels and comfort levels are achieved by varying the thickness, weight and formulation of the visco-elastic foams and the base foams. Latex and memory foam mattresses each provide a unique feel. This type of mattress is good at relieving pressure on painful joints, but is usually more expensive than spring mattresses.
Memory foam is affected by temperature. In a cool bedroom, a memory foam mattress will feel firmer than it does in a warm bedroom. Memory softens and conforms to the sleeper in response to body temperature and body weight. Traditional memory foam molds to the body creating a depression the sleeper must roll out of when changing sleep positions. Mattress manufacturers have responded to this issue by using "faster response" memory foams. They spring back more quickly when the sleeper moves. Foam mattresses are also known to generally "sleep warmer" than innerspring mattresses. Mattress makers have addressed the issue with "open-cell" memory foams, pinhole cored memory foam, gel-infused memory foams, channel-cut foam cores, reticulated foam support layers and other technologies to improve air circulation through all-foam beds.
Mattresses can also be made from bladders of some fluid, notably water or air. These date to antiquity – goatskin bladders filled with water were used in Persia at least as early as 3600 BCE – and gained increased popularity in the 20th century with improved manufacturing.
Air mattresses use one or more air chambers instead of springs to provide support. Quality and price can range from inexpensive ones used occasionally for camping, all the way up to high-end luxury beds. Air mattresses designed for typical bedroom use cost about the same as inner-spring mattresses with comparable features.
Air bladder construction varies from a simple polyethylene bag to internally baffled, multiple chambers of latex (vulcanized rubber) or vinyl with bonded cotton exteriors. Mattresses may have a layer of foam above the air chambers for added cushioning, and may be enclosed in a cover. Some such beds are termed soft-sided air beds.
Adjustable-firmness air mattresses are available. Some allow independent adjustment of each side of the bed. They are made in a variety of models from basic, no-frills ones that measure about 7" in height, to high-profile, 15" tall hybrids that contain several types of foam, pillow tops, and digital pumps with memory for individual pressure settings.
Air mattresses for medical use
Adjustable-firmness mattresses for medical use have special control mechanisms. In the 1990s self-adjusting air beds that automatically change their pressure periodically, or inflate and deflate several air chambers alternately, were introduced. The intention of these periodic changes is to reduce problems with decubitus ulcers (bed sores), though as of 2008[update] the effectiveness of these techniques was still being researched.
Self-inflating air mattresses
Air mattresses for camping are available which are filled with foam which itself provides little support, but expands when the air valve is opened allowing air to enter, so the mattress (nearly) inflates by itself. This is especially useful for campers who carry their equipment as, unlike with normal air mattresses, no pump is needed for inflating. Available brands include Aerobed, Coleman, Therm-a-Rest and others.
Safety concerns for infants
The U.S. Consumer Product Safety Commission advises consumers not to let infants sleep on air mattresses. This is motivated by reports of deaths, mostly infants younger than 8 months of age, who were placed to sleep on air mattresses, and either suffocated in a face down position on an air mattress or died due to suffocation after falling into gaps between the mattress and bed frame, or the mattress and adjacent furniture or wall.
A waterbed is a mattress with water in its interior instead of metal coils or air. Waterbeds can be lined with different layers of fiber to achieve the level of firmness the user desires. Waterbeds are well known for providing support to the spine and other body parts, similar to the other mattress types. There are several options of support which range up to 100% waveless, where the user does not notice he/she is laying upon a waterbed.
Many parameters determine mattress quality. Laboratory test methods have been established for some of these parameters, such as pressure distribution, skin microclimate, hygiene, edge support, and long-term stability. Some of these have been developed by Duncan Bain, working on behalf of the UK's Medicines and Healthcare products Regulatory Agency.
Other parameters, such as firmness, are more specific to the sleeper. In general, firm mattresses are recommended for stomach and some back sleepers, soft mattresses are recommended for side sleepers, and medium mattresses are recommended for the majority of back sleepers. Double mattresses are available with a softer and a firmer part, or with adjustable firmness levels, to accommodate sleepers with different preferences who share a bed.
Mattresses deteriorate over time, and the lifespan of a mattress depends on a variety of factors, notably materials, manufacturing quality, care, and the vigorousness of use. A poor quality foam comfort layer can deteriorate noticeably in 1 year, while a quality latex core can last 20 years or more; innerspring cores typically last around 10 years. The comfort layer is almost invariably the first area to fail, which is why mattresses are often double-sided, to extend the lifespan. A separate topper may be used instead of or in addition to a comfort layer, which reduces wear and is replaceable without replacing the entire mattress.
In the United States, mattress warranties are typically for 10 years or 20 years, sometimes 25 years, though this specifically addresses manufacturing defects and faster-than-normal deterioration, not expected deterioration with time. In the United States, as of 2008[update] there is a general expectation that mattresses should last about 10 years, and this is the average number of years Americans keep mattresses, though this varies by age group. This expectation is based on a number of factors, including: sales pitches; the expectation that mattresses will last the length of their warranty, hence 10 years or 20 years, accordingly; and comparison with other household items.
Mattress replacement cycle is a key driver of income and profits for the mattress industry – a 5-year replacement cycle yields double the sales of a 10-year replacement cycle, for instance – so the mattress industry has a financial incentive to shorten the replacement cycle. Notably, the International Sleep Products Association (ISPA) established the Better Sleep Council (BSC) in 1979 with the stated goal to "shorten the mattress replacement cycle", in addition to encouraging people to "invest in better bedding".
In terms of scientific studies, an industry-funded 2006 study by researchers at Oklahoma State University (funded by the BSC) of 59 people with poor sleep who received free new replacement mattresses for their existing mattresses 5 years or older (average age 9.5 years) found improved sleep, particularly when the existing mattresses was cheap. A follow-up paper by some of the same authors with additional statistical analysis reinforced these conclusions. The BSC has subsequently cited this study in the ISPA-published news magazine for mattress manufacturers, BedTimes, to advocate a more frequent replacement cycle, specifically to "consider replacing a mattress every five to seven years"; the recommendation is based largely on this study.
Maintenance and care
The main wear problems that can occur with a mattress are sagging, mildew, and staining. These are prevented by proper support, rotation and flipping, keeping it dry, and using a mattress pad or protector. Some symptoms of a broken or worn-out mattress include springs which can be felt poking through the upholstery layer, visible permanent sagging or deformity, lumpiness, and excessive squeaking.
Mattresses require a solid foundation which does not itself sag – a sagging foundation, such as by weak slats on a wide bed, will in turn cause the mattress to sag. Consistently sleeping in the same place and body position causes excessive wear, and thus rotating or flipping mattresses is used to reduce this: double-sided mattresses can be alternately flipped width-wise (about the long axis) and length-wise (about the shorter axis), or alternately flipped and rotated; while single-sided mattresses are only rotated, which is simpler but less effective. Flipping/rotation schedules vary between materials and manufacturers, but typically recommended is monthly for the first six months, and every two or three months thereafter. Foundations should also be rotated, if possible, though less frequently – rotating box springs twice a year is recommended. While sagging is undesirable, some level of indentation (about 8 cm or 1.5 inches) is natural if natural materials are used in a comfort layer.
Excessive wear on mattresses, such as folding and bending, placing heavy objects in one spot, or excess force on the handles, will also cause more rapid deterioration. Care should particularly be taken during transport or storage.
Mattresses require ventilation to remain dry and prevent mildew, and thus should not be placed directly on the floor or on a solid surface – slats or a box spring provide space for airflow, while solid wood or plywood (as in cheap bunkie boards) does not. Additional ventilation is recommended for natural materials, in which case leaving the mattress "naked" after stripping sheets (for example while laundering) is recommended. If a mattress is allowed to become damp, for example by wet cleaning, mildew may develop inside the upholstery; cleaning with a vacuum cleaner or mild surface cleanser and a slightly damp cloth avoids this.
Mattresses absorb fluids and stains readily, notably from nightly sweating (which results in a yellow stain) and other bodily fluids (sexual fluids or menstruation), in addition to accidental spills. These visibly stain the ticking, and seep through into lower layers. In addition to being unhygienic, hard to launder, and unsightly, such stains typically void a warranty. Thus a mattress protector is suggested to protect the mattress; this can be removed and cleaned separately, and replaced if damaged.
- "Mattress". Dictionary.com. Retrieved 2012-05-26.
- "Mattress: Word History." The American Heritage Dictionary.
- "Divan". Dictionary.com. Retrieved 2012-05-26.
- Nelles, Barbara. "The Inside Story." BedTimes Magazine. July 2009. Retrieved 2011-9-1
- History of California King-sized beds
- Aerospace Technology Innovation May/June 1998
- "Company History." Simmons website, www.simmons.com. Retrieved 2011-8-21.
- based on "Common Mattress Dimensions". Precious Bedding Company.
- Haex, Bart (2005). Back and Bed: Ergonomic Aspects of Sleeping. CRC Press. ISBN 0-415-33297-4.
- Which, published by Consumers Association: Mattresses: Choosing the best type of mattress
- "At High Point: Shifman highlights its handcrafting". BedTimes Magazine. Retrieved 2/11/14. Check date values in:
- Nelles, Barbara (Feb 2012). "New features rev up steel frames & support systems". BedTimes Magazine. Retrieved 2/11/14. Check date values in:
- James, Gary. "Gel Foams Meet Fast-Growing Demand." BedTimes Magazine. Oct. 2012. Retrieved 2012-9-26.
- Nelles, Barbara. "Dress Up: Mattress Fabrics take on many roles." BedTimes Magazine, November 2009. Retrieved 2011-8-21.
- Nelles, Barbara. "Judging a Bed by its Cover." BedTimes Magazine. October 2011. Retrieved 2012-1-2.
- "Flexible Polyurethane Foams (FPFs) Used in Upholstered Furniture and Bedding." American Chemistry Council: Center for the Polyurethanes Industry. 2008. Retrieved Aug. 15, 2011.
- "Product Watch: Green foams grabbing the spotlight." BedTimes Magazine. Feb. 2010. Retrieved Aug. 15, 2011.
- "The future of foam: An ever-widening sphere of influence. BedTimes" Magazine. February 2003. Retrieved Aug. 15, 2011.
- "About Natural Latex." Savvy Rest. Retrieved Aug. 21, 2015.
- Nelles, Barbara. "Trends in Springs and Foam." BedTimes Magazine, Aug. 2011. Retrieved 2013-8-13
- Nelles, Barbara. "What's in the air? Category clearly getting off the ground." ''BedTimes Magazine. June 2006.
- Alternating pressure air mattresses as prevention for pressure ulcers: A literature review International Journal of Nursing Studies, Volume 45, Issue 5, Pages 784-801 (May 2008)
- Air Mattresses are Not for Infants. Bethesda, MD: U.S. Consumer Product Safety Commission, 2012.
- Bain, Duncan. “Pressure Reducing Mattresses.” MHRA. April 2004.
- Simon, Tim (10 January 2015). "What type of Sleeper are you and how does this relate to your mattress choice?". Regal Sleep Solutions. Retrieved 11 February 2015.
- "Oklahoma State University research shows importance of new mattress". BedTimes. April 2008.
- "BSC builds on a quarter century of PR to move industry forward." BedTimes Magazine. September 2004. Retrieved 2012-9-30.
- Footnotes, "Changes in back pain, sleep quality, and perceived stress after introduction of new bedding systems"
- Jacobson, Bert H.; Boolani, Ali; Smith, Doug B. (Mar 2009). "Changes in back pain, sleep quality, and perceived stress after introduction of new bedding systems". J Chiropr Med. 8 (1): 1–8. doi:10.1016/j.jcm.2008.09.002. PMC 2697581.
- Jacobson, Bert H.; Wallace, T. J.; Smith, Doug B.; Kolb, T. (2008). "Grouped comparisons of sleep quality for new and personal bedding systems". Applied ergonomics 39 (2): 247–54. doi:10.1016/j.apergo.2007.04.002. PMID 17597575.
- Nancy Butler (April 2008). "Better Sleep Council consumer research findings on mattresses and sleep". BedTimes.