If you’ve been a long time reader or have had the chance to browse through our previous posts, you know that we've posted a lot on infant sleep over the years. We know from experience that one of the hardest parts of being a new parent is adjusting to the lack of sleep that comes with caring for such a tiny baby. In the past, we've explained why babies don’t sleep through the night (see Baby Behavior Basics Part 1), how babies sleep at different ages and the difference between falling asleep and staying asleep (see The Science of Infant Sleep Part 1, Part 2, and Part 3), and we’ve provided tips for sleep deprived parents (see Dealing Realistically with Postpartum Sleep Deprivation Part I and Part 2.
As we’ve discussed infant sleep and parental fatigue, both in person at speaking engagements and with readers of this blog, we’ve gotten a lot of questions about the use of noise machines to help babies sleep better. While we understand the concept (white noise is repetitive stimulation, which we know calms babies), there are a few reasons we’ve been careful not to recommend use of these machines for babies. First, we know that babies, especially young babies, need to wake often (see Baby Behavior Basics Part 1) and second, we didn’t know much about the safety of these machines for use with babies. So, when a recently published study about the safety of infant sleep machines showed up in the news, it caught our eye.
The authors evaluated 14 machines that are widely available in the US and Canada. Each machine played a range of 1 to 10 different sounds, including nature noises (for example, wind, water, birds, etc) white noise, mechanical sounds (traffic, trains, etc) and heartbeat sounds. During the measurements, the authors tried to recreate the experience of using these machines in real life. They used a microphone set-up to mimic an infant’s ear and measured the sound level at 3 different distances, 30 cm (~11.8 inches) similar to crib rail placement), 100 cm (~ 3 feet) to replicate placement on a table near the crib, and 200 cm (~6.5 feet) to represent a machine placed across the room.
Not surprisingly, the closer the machine was to the microphone, the louder the measurement. At the crib rail and bedside table positions, all 14 machines exceeded the recommended levels for hospital nurseries. Three of the machines were so loud that they would be considered dangerous for adults when exposed for 8 hours (like overnight, for example). Even when placed across the room, 13 of the 14 measured louder than recommended.
Like usual, the authors state that more research is needed. They did not collect information about how these machines are usually used in real life, so this study does not provide information about where parents usually place the machines, how long they typically stay on, or which volume setting is used most (they measured at the loudest setting). However, they point out that all of these machines are easily available for purchase with very little instruction for use or safety information and that there is clear evidence that inappropriate noise exposure can change infants’ heart rates, disrupt sleep quality and duration, and even lead to hearing loss.
Reference: Hugh, Sarah C et al. Infant Sleep Machines and Hazardous Sleep Pressure Levels. Pediatrics Volume 133, Number 4, April 2014.
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