A study from the University of Pennsylvania indicates that noises typically promoted to aid sleep, such as pink noise, might have negative effects on sleep quality. Sound machines and mobile apps that play pink noise are commonly used to help individuals sleep better and block out environmental sounds like traffic or planes. However, research conducted with 25 healthy participants in a controlled sleep lab suggests these tools may lead to unintended consequences.
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Dr. Mathias Basner, a professor of psychiatry at the university, led the study, which found that pink noise decreases the amount of REM sleep experienced by sleepers. REM sleep, or Rapid Eye Movement sleep, occurs about 90 minutes after falling asleep and is crucial for emotional regulation, learning, and neurodevelopment.
Participants were monitored under various conditions, including silence, constant pink noise, intermittent environmental noise from sources like jets and cars, and combinations of these. Sleep was assessed using polysomnography, which tracks brain waves, eye movements, and muscle tone.
The study revealed that intermittent environmental noise significantly disrupted deep sleep, an early-night stage linked to physical restoration and memory consolidation. When both pink noise and environmental sounds were present, all aspects of sleep deteriorated, with participants experiencing losses in both deep and REM sleep. Moreover, playing pink noise alone also resulted in decreased REM sleep.
While the study involved adult participants, Basner expressed concern regarding the implications for children, who typically spend more time in REM sleep than adults. He is worried about the potential effects of parents using sound machines to assist their children’s sleep.
As an alternative, Basner suggests using earplugs to minimize environmental noise without adding constant background sound. In the study, earplugs allowed participants to recover over 70% of the deep sleep lost due to environmental interruptions, without harming their REM sleep. Basner noted that this research was a short-term laboratory study and expressed his intention to expand the investigation into real-world settings, particularly targeting habitual users of sound machines.
For now, he recommends using sound machines at the lowest volume, setting timers to turn off noise after falling asleep, and adhering to traditional sleep hygiene practices, such as maintaining a dark, cool, quiet room and establishing consistent bedtime routines.