Scientists Challenge Pink Noise Benefits: Deep Sleep and REM Affected

Pink noise, a sound many people play to mask background disturbances and promote sleep, may actually worsen sleep quality. Researchers from the University of Pennsylvania, working with colleagues from Europe and Canada, found that pink noise reduced time spent in essential sleep stages, including deep sleep. The study appeared in the journal Sleep.

Why Pink Noise Sounds Different

Pink noise differs from white noise because it carries more energy at lower frequencies. This characteristic gives it a softer and more natural sound, often compared to rainfall or a waterfall. Many sleep apps and sound devices market pink noise as a tool for better rest, yet recent findings challenge those claims.

Laboratory Study Reveals Sleep Disruptions

Scientists tested how various sounds influenced the sleep of 25 adults. Participants spent seven nights in a controlled laboratory environment where researchers played different background conditions: pink noise at 50 dB, aircraft noise, a combination of both, or complete silence. After waking, participants completed cognitive tests and evaluated their sleep quality.

Unexpected Effects on Deep and REM Sleep

The results surprised the research team. Aircraft noise reduced deep sleep by approximately 23 minutes. Pink noise shortened REM sleep by nearly 19 minutes. The combination of aircraft noise and pink noise produced even greater disruptions. Participants woke more frequently and described their sleep as lighter and less restorative.

Earplugs partially offset the negative effects of environmental noise, suggesting that physical noise reduction may work more effectively than artificial masking sounds.

Why REM Sleep Matters

Matthias Basner, a professor of sleep and chronobiology, emphasized the importance of REM sleep for memory, emotional regulation, and brain development. Because children spend more time in REM sleep than adults, sound environments that disturb this stage may pose greater risks for younger populations. Despite this, sound machines often appear near infants' beds.

Broader Health Implications

Researchers noted that REM sleep disturbances frequently occur in conditions such as depression, anxiety disorders, and Parkinson's disease. These connections highlight the potential significance of seemingly harmless sleep aids. Children may face particular vulnerability due to their higher proportion of REM sleep.

Scientists urge caution when using broadband noise for sleep, especially for newborns and young children. They also stress the need for further studies to better understand how continuous background sounds influence long-term sleep health.