Changes in sleep and wake in response to different sleeping surfaces: A pilot study W. Vaughn McCall a, * , Niki Boggs a , Alan Letton b a Department of Psychiatry and Behavioral Medicine, Medical Center Blvd, Wake Forest University School of Medicine, Winston-Salem, NC 27106, USA b Sealy, Inc, Trinity, N.C., USA article info Article history: Received 26 November 2010 Accepted 7 June 2011 Keywords: Mattress Sleep Pressure mapping abstract Six married couples (12 adults, mean age 34.8 years) were randomized as couples in a cross-over design to sleep on a queen-size conventional mattress for 2 weeks and a specially-designed pressure-relief mattress for 2 weeks. The pressure-relief mattress was designed to reduce the number of contact points exceeding 30 mm Hg. Actigraphic measurements of sleep and self-reports of sleep and daytime symp- toms were collected at baseline for 2 weeks on each couple’s home mattress and box springs at home, followed by 2 weeks of data collection on each randomized mattress for a total of 6 weeks of data collection. Pressure maps were created for each participant on each sleeping surface. There were no significant differences between the randomized sleeping surfaces for any measure of actigraphic sleep or self-reported sleep and daytime symptoms. However, poor pressure relief performance of the home mattress was associated with better actigraphic sleep on the randomized pressure-relief mattress. We conclude that while pressure-relief mattresses may not be universally preferred, baseline characteristics of the sleeper and/or their mattress may explain performance and sleeper preferences on future mattress selection. Ó 2011 Elsevier Ltd and The Ergonomics Society. All rights reserved. 1. Introduction The continuity and quality of sleep is well known to be sensitive to the characteristics of the sleeping environment. Particularly salient features include noise, temperature-humidity, light, the sleeping partner, and the sleeping surface. These features are a part of every sleeper’s experience every night, and three of them can be objectively quantified: noise (decibels), temperature-humidity, and light (lux), and can be experimentally manipulated with relative ease (Marks & Griefahn 2007; Okamoto-Mizuno et al., 1999; Schnelle et al., 1999; Stosic, Belojevic, & Milutinovic 2009). In contrast with what is known about the impact of sound, temperature, and light, less is known about the impact of the sleeping surface, in part because the performance of the sleeping surface is harder to quantify. Research on sleeping surfaces typically limits description of the sleeping surface to generic types such as “futon”, “conventional spring mattress”, or “water bed”, or to purely qualitative categories such as “soft” or “firm”. These categories do not directly describe the mechanical effect of the sleeping surface upon the sleeper, nor do they allow for rigorous replicability. The importance of this knowledge gap regarding sleeping surfaces is reflected in that up to 7% of American adults have reported that their mattress was a source of sleeping problems (Addison et al., 1986). The design of a sleeping surface can affect body support and weight-load distribution, thereby affecting capillary perfusion of soft tissues and strain upon joints. Some authors have suggested that 30 mm Hg serve as the target threshold for the skin-surface interface, below which skin pressures should be maintained to assure perfusion (Bridges, Schmelz Joseph, & Mazer, 2003). A classic study by Landis showed that mean arteriolar pressure in the capil- lary bed was 32 mm Hg, (Landis, 1930) while de Graaff et al reported that mean systolic capillary pressure was 26.2 mm Hg (de Graaff et al., 2001). As a result, 30 mm Hg seems a reasonable standard for the upper limit of acceptable pressure between a sleeping surface and the skin in order to remain below the critical capillary closing pressure, and maintain capillary perfusion to soft tissues. Failure to provide an adequate distribution of load may lead to more frequent changes in body position for the purpose of re-establishing blood flow or relief of joint strain (Gardner and Grossman, 1975). Body movements are a normal part of healthy sleep, and include major movements such as changes in body position from lateral to supine, as well as minor movements to re-distribute load without * Corresponding author. Tel.: þ1 336 716 2911; fax: þ1 336 716 6830. E-mail addresses: vmccall@wfubmc.edu (W. Vaughn McCall), alan@lettonmctier. com (A. Letton). Contents lists available at ScienceDirect Applied Ergonomics journal homepage: www.elsevier.com/locate/apergo 0003-6870/$ e see front matter Ó 2011 Elsevier Ltd and The Ergonomics Society. All rights reserved. doi:10.1016/j.apergo.2011.06.012 Applied Ergonomics 43 (2012) 386e391