A firm recommendation: measuring the softness of infant sleep surfaces

Background Approximately 3600 sudden unexpected infant deaths (SUID) occur annually in the United States, and a quarter of SUIDs are caused by unintentional suffocation and strangulation in bed, with soft bedding use being a significant risk factor. Therefore, The American Academy of Pediatrics (AAP) recommends infants sleep on a “firm” surface, though neither an objective definition nor national standard has been established. The purpose of this study is to report on the performance of a device that measures mattress softness and to provide quantitative values of softness for various infant sleep surfaces. Methods In collaboration with the authors and a national child product safety organization (Kids in Danger), University of Michigan engineering students designed and validated a device that measures the vertical depression (softness) of a simulated 2-month-old’s head on a sleep surface. A total of 17 infant sleep surfaces − 14 household surfaces and 3 hospital mattresses - were measured between April 2019 and January 2020. The average softness of each surface was calculated. Surfaces were also measured with soft bedding, which included an infant fleece blanket, and firm and soft pillows. Results The average softness for the 14 household sleep surfaces ranged from 7.4–36.9 mm. The 2019 cribette playard and the 2018 infant spring had similar softness (21 mm) as the 2018 and 2019 adult foam and 2015 sofa. An infant’s fleece blanket folded once added an additional 2.3–6.5 mm of softness, folded twice added 4.8–11.6 mm, and folded three times added 11–21.8 mm. Using a firm pillow added 4.0–20.9 mm of softness while using a soft pillow added 24.5–46.4 mm. The softness for the 3 hospital sleep surfaces ranged from 14 to 36.9 mm, with the infant bassinet being the firmest and the pediatrics mattress being the softest. Conclusions We found a wide range of softness among sleep surfaces, with some infant mattresses as soft as some adult mattresses. Adding blankets and pillows to mattresses measurably increased softness. Quantifying sleep surface softness will advance our understanding of how softness relates to SUID risk. We hope this new information will further inform safe infant sleep recommendations and improve mattress safety standards nationally.