Observational study finds pink noise reduces REM sleep duration in healthy adults — Evidence Review

Pink noise, often used in sleep aids, may actually reduce REM sleep and disrupt restorative sleep stages, according to a new study; this contrasts with some earlier research but aligns with recent findings questioning the benefits of continuous background noise. Most related studies report mixed or inconclusive effects of broadband noise on sleep, highlighting ongoing debate in the scientific community—see the original source for details.

• While some previous studies suggested pink or white noise can improve sleep onset or depth, others have found possible reductions in REM sleep or little benefit to overall sleep quality, mirroring the new study's findings 3 5 6 7.
• The new research aligns with evidence that high background noise (even when intended to mask disruptive sounds) can decrease deep and REM sleep, although some studies have reported improvements in subjective sleep quality, especially in noisy hospital environments 2 4 10 11.
• Systematic reviews consistently note that the evidence for continuous broadband noise as a sleep aid is weak or inconclusive, and call for higher-quality studies and consideration of potential adverse effects, especially in vulnerable populations like children 3 5.

Study Overview and Key Findings

With sleep apps and sound machines gaining popularity, questions about their impact on restorative sleep have become increasingly relevant. This study from the University of Pennsylvania Perelman School of Medicine addresses these concerns by rigorously evaluating the effects of pink noise and earplugs on sleep architecture, particularly REM and deep sleep, in a controlled laboratory setting. The research uniquely examines not just subjective sleep quality but also objective sleep stage changes and cognitive outcomes after exposure to various sound conditions.

Property	Value
Organization	University of Pennsylvania Perelman School of Medicine
Journal Name	Sleep
Authors	Mathias Basner, MD, PhD
Population	Healthy adults aged 21 to 41
Sample Size	25 participants
Methods	Observational Study
Outcome	Effects of pink noise and earplugs on sleep quality and stages
Results	Pink noise reduced REM sleep by nearly 19 minutes.

Literature Review: Related Studies

To understand how these findings fit within the broader scientific landscape, we searched the Consensus paper database, which includes over 200 million research articles. The following search queries were used to locate relevant studies:

1. sound machines sleep quality effects
2. pink noise REM sleep duration
3. white noise sleep disturbances studies

Below is a summary of key topics and findings from the literature:

Topic	Key Findings
Does broadband noise (pink/white noise) improve or disrupt sleep quality?	- Evidence for improvements in sleep quality from continuous white or pink noise is inconsistent and generally low in quality; some studies report no adverse effects with short-term use 3 5. - Several studies show pink noise may deepen sleep but reduce REM duration 6 7.
What are the effects of environmental and mechanical noise on sleep architecture?	- High background noise, including mechanical or ventilation noise at or above 50 dB(A), can reduce deep and REM sleep and increase light sleep or wakefulness 2 4. - White noise may help mask disruptive noise and improve subjective sleep quality in hospital settings 10 11.
Are there population-specific considerations (e.g., children, patients, shift workers)?	- Children and vulnerable populations (such as premature infants) may be particularly sensitive to changes in sleep stage distributions caused by noise, though some short-term studies show no adverse effects 5 12. - In patients, white noise can improve perceived sleep when environmental noise is high 10 11 12.
How do tailored auditory stimuli (e.g., binaural beats, ASMR) compare to broadband noise?	- Combining binaural beats with ASMR triggers can induce sleep and promote psychological comfort, potentially offering an alternative to continuous broadband noise 1. - Rhythmic acoustic stimulation (timed bursts) may enhance slow-wave sleep without continuous noise exposure 8.

Does broadband noise (pink/white noise) improve or disrupt sleep quality?

The literature presents a mixed picture regarding the use of broadband noise for sleep. Systematic reviews conclude that evidence for sleep improvements from continuous pink or white noise is weak, inconsistent, or of very low quality, despite widespread consumer use. Some experimental studies suggest pink noise can deepen sleep by increasing stage 2 and deep (N3) sleep, but often at the expense of REM sleep, mirroring the new study's main finding 3 5 6 7. Importantly, most short-term studies report no significant adverse effects, but the long-term impact on restorative sleep stages remains uncertain.

• Systematic reviews find little strong evidence that continuous broadband noise improves sleep outcomes, and highlight the need for better-quality studies 3 5.
• Some studies report an increase in deep or stable sleep under pink noise, but a reduction in REM sleep, raising questions about the trade-offs involved 6 7.
• No significant adverse effects have been reported for short-term use in most populations studied, but effects on cognitive or emotional outcomes are not well explored 5.
• The new study's finding of reduced REM sleep with pink noise aligns with prior research suggesting possible negative consequences for sleep architecture 7.

What are the effects of environmental and mechanical noise on sleep architecture?

Research consistently shows that high levels of background noise—whether from environmental sources like traffic or mechanical systems—can negatively impact sleep quality by reducing deep and REM sleep and increasing awakenings or light sleep. White noise is sometimes used in clinical settings to mask these disruptive sounds, with some success in improving subjective sleep quality, especially among hospital or ICU patients exposed to high noise environments 2 4 10 11.

• Background noise in hospital or ICU settings is linked to reduced subjective and objective sleep quality 2 4.
• Mechanical ventilation noise at or above 50 dB(A) decreases deep and REM sleep, consistent with the new study’s findings at similar decibel levels 4.
• Application of white noise in clinical settings can mask environmental disturbances and help maintain sleep in some patient populations 10 11.
• The balance between masking disruptive noise and avoiding additional sleep stage disruption remains a key challenge.

Are there population-specific considerations (e.g., children, patients, shift workers)?

Some populations may be more susceptible to the effects of broadband noise on sleep stages. Children, who spend more time in REM sleep and are in critical stages of brain development, may be particularly vulnerable to disturbances in REM caused by continuous background noise. In contrast, patients in noisy hospital environments may benefit from white noise as a masking tool, although the long-term safety and developmental impacts, especially in infants and children, are still not fully understood 5 12.

• Children and infants spend more time in REM sleep, and evidence on the safety of continuous noise exposure in these groups is limited 5.
• In neonatal intensive care, white noise has shown some positive effects (e.g., weight gain), but sleep-wake pattern improvements are not consistently demonstrated 12.
• Hospitalized adults and patients exposed to high environmental noise may experience improved sleep quality with white noise masking, but these results may not apply to healthy individuals or home settings 10 11.
• The new study’s caution regarding the use of pink noise for children is supported by concerns about vulnerable populations in the literature 5 12.

How do tailored auditory stimuli (e.g., binaural beats, ASMR) compare to broadband noise?

Emerging research suggests that customized auditory approaches, such as binaural beats combined with ASMR triggers or rhythmic acoustic stimulation, may offer sleep-promoting benefits without the potential downsides of continuous broadband noise. These methods can induce sleep-related brainwave patterns and enhance slow-wave sleep without reducing REM sleep, and may provide greater psychological comfort 1 8.

• Combined binaural beats and ASMR triggers can effectively induce sleep and promote user comfort, providing an alternative to continuous noise 1.
• Rhythmic, non-continuous pink noise bursts delivered during naps have been shown to enhance slow-wave activity, potentially supporting restorative sleep without broadly suppressing REM 8.
• These targeted approaches may reduce negative effects on sleep architecture compared to continuous broadband noise, an area that warrants further study 1 8.
• The new study’s findings highlight the need for research into safer and more effective auditory sleep aids.

Future Research Questions

Given the mixed and often inconclusive evidence, future research is needed to clarify the long-term health effects, optimal use, and safety of broadband noise as a sleep aid—especially in vulnerable populations. The limitations of current studies, including small sample sizes, short durations, and lack of focus on developmental or cognitive outcomes, underscore the importance of further investigation.

Research Question	Relevance
What are the long-term effects of continuous broadband noise exposure on sleep architecture and cognition?	Long-term studies are lacking, and potential cumulative effects on REM and deep sleep, as well as cognitive outcomes, are not well understood 3 5 7.
How do different colors of noise (pink, white, brown) differentially impact sleep stages?	Comparative studies are needed to determine whether specific types of broadband noise have unique effects on NREM, REM, and overall sleep quality 5 6 7.
What are the effects of broadband noise exposure on sleep in children and other vulnerable populations?	Children and infants may be particularly sensitive to disruptions in REM sleep; research on developmental and health impacts is limited and urgently needed 5 12.
Are tailored auditory stimuli (e.g. binaural beats, ASMR) safer or more effective than continuous noise for sleep induction?	Personalized auditory interventions may offer sleep benefits without suppressing REM or deep sleep, but direct comparisons and safety data are sparse 1 8.
What are the optimal sound intensity levels for noise-based sleep aids to maximize benefit and minimize harm?	Many studies use 50–60 dB(A), but effects at lower or higher intensities are not well characterized, and there may be a threshold above which sleep disruption occurs 4 6 7.