Mattresses Matter: Ergonomic Guidelines

How to Sleep Soundly

Alan Hedge, PhD, CPE
Professor, Ergonomics
Cornell University
Ithaca, NY
In Hans Christian Andersen's fairytale the Princess and the Pea, a princess is unable to get a good nights sleep because a pea has been placed under her mattress, actually 20 mattresses, piled high! One moral to this tale is that the quality of what you sleep on matters to the quality of your sleep. In fact, when we are asleep our body is compressed by gravity in a different way to when we stand upright, and we need to be fully supported by the mattress and it's supporting structures. For this reason the mattress has been called an 'antigravity machine' that makes it possible to maintain the natural shape of the spine when sleeping.[1]

Although we spend around one-third of our life lying on mattresses, and although it is estimated that about half of all Americans experience at least occasional sleep difficulties there has been relatively little scientific study of mattress design.[2] Poor mattress design can create inappropriate body support, and this in turn may cause muscle discomfort and back pain.[3] So what are the features of a good mattress? Does it matter if it's too hard or too soft? Does it matter if it's an orthopedic mattress? Is a mattress even important?

Recent Mattress Study
In a recent study of mattress ergonomics that tested 12 women, lying on an incompressible wooden surface was compared with various mattresses. All of the mattresses were judged as significantly more comfortable than the wooden surface, but there were no significant differences between mattress types, even though these included orthopedic and normal designs. Measures of shoulder, elbow, hip, knee and ankle body contact pressures showed few significant differences, and surprisingly there were no significant associations between measures and the comfort ratings.[4]

However, how hard or soft a mattress feels is thought to be an important factor in reducing or preventing back pain.[5] Comparison of sleeping on a futon or a softer air mattress showed that sleep onset latency, waking after sleep onset and the sleep efficiency index were comparable for both mattresses but subjective sleep evaluation tended to be better for the air mattress.[6] A study of sleep quality and bed firmness showed that 4 of 9 male subjects slept significantly better on the softer mattresses and 2 on the harder mattress. The greatest difference in sleep quality occurred when changing from the subject's own mattress to one of the test mattresses, and the authors concluded that it may take several days to adapt to a new sleep surface.[7] This may be why business travelers often report sleep difficulties.[8]

Guidelines for Choosing a Mattress
So what should you look for in a mattress? The Cornell University's Ergonomics group gives some guidelines for choosing your mattress.[9]

Look for a mattress that is:

> Designed to conform to the spine's natural curves and to keep the spine in alignment
when you lay down.

> Designed to distribute pressure evenly across the body to help circulation, decrease body movement and enhance sleep quality.

> Designed to minimize the transfer of movement from one sleeping partner to the other.

> Designed with perimeter edge support.

Pillow Selection
Also, look for a pillow that complements the mattress, and choose pillows that are:

> Designed to keep the spine in natural alignment.

> Designed for maximum adjustability.

> Designed with the ability to be fluffed to fit the unique contour, shape, and sleeping
posture of the user.

> Designed to support different sleep positions:
Side sleeper - Back sleeper - Stomach sleeper.

> Designed to support the head.

> Designed to provide tactile softness.

> Designed to eliminate pressure points.

> Designed to increase facial air circulation.

> Designed as hypoallergenic.

Remember, you'll spend around some 24 years of your life sleeping, so take time to choose the best sleep system (i.e. the mattress, support structure, pillows and sheets) that you can and it will improve your sleep and your quality of life.

References

1. Buti, L.B. (1995) The Art of Sleeping: Mattress Ergonomics, Ergonomia, 6, 11-15.

2. National Sleep Foundation (1999) Help Yourself to a Good Night's Sleep (http://www.sleepfoundation.org/publications/goodnights.html)

3. Huysmans, T., Haex, B., Van Audekercke, R., Vander Sloten, J., Van Der Perre, G., Van Haute, R., and Baeteman, J. (2000) 3D Postural Analysis for the Evaluation of Spinal Deformations during Sleep, In K. Landau (ed.) Ergonomic Software Tools in Product and Workplace Design, Verlag ERGON, Stuttgart, Germany, pp. 72-85

4. Buckle, P., Fernandes, A (1997) Mattress Evaluation - Assessment of Contact Pressure, Comfort and Discomfort, Applied Ergonomics, 29 (1), 35-39.

5. Hanel, S.E., Dartman, T., Shishoo, R. (1996) A Comparsion of Measuring Methods for Comfort Rating of Beds, In A. Mital, H. Krueger, S. Kumar, M. Menozzi and J. Fernandez (eds.) Advances in Occupational Ergonomics and Safety I, Volume 2, International Society for Occupational Ergonomics and Safety, Cincinnati, Ohio, USA, pp.783-787.

6. Okamoto, K., Mizuno, K., Okudaira, N. (1997) The Effects of a Newly Designed Air Mattress upon Sleep and Bed Climate, Applied Human Science, 16 (4), 161-166.

7. Bader, G.G. and Engdal, S. (2000) The Influence of Bed Firmness on Sleep Quality, Applied Ergonomics, 31 (5), 487-497

8. National Sleep Foundation Sleep and the Traveler. (http://www.sleepfoundation.org/publications/travel.html)

9. Cornell University (2000) Hotel Ergonomics - Guest Room and Office Design (Kelley Dallas) (http://ergo.human.cornell.edu/HotelEzra/intro.htm)

Last Updated: 08/24/2007
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Peer Review by Leading Specialists

    Richard D. Guyer, MD

    While Professor Hedge had written an excellent article on the ergonomic guidelines of choosing a mattress, the actual process of choosing a mattress when one goes shopping becomes a fairly intimidating experience. In general each of the large manufacturers produces many different grades of mattresses, usually 4 or 5. The more expensive the mattress the more support (more springs per square foot, for example) and the thicker the padding on top of the mattress (commonly called “pillow top”). When trying to compare one mattress to another manufacturer’s mattress, it becomes even more confusing. It is at this point that one should rely on a knowledgeable salesperson’s recommendations and most importantly how it feels to the individual. Now, for the practical pointers: I always recommend to my patients that they choose either the middle or upper middle of the line mattress from one of the name brand mattress companies. The firmest mattress is not necessarily the best, but one of the upper line mattresses will give more than adequate support. The pillow top mattresses, which usually are the top of the line, are not necessarily the best because one often loses the firmness of the mattress below. However, there are many which do provide excellent support while allowing the body to conform to the pillow top padding. I would recommend to the consumer that they buy it from a reputable store that allows them to return the mattress within 30 days. If you have been living with a worn out mattress without much support, buying a new mattress will often help that morning backache. Remember it is how the mattress feels to you that determines which the best for you.
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