Philadelphia — For many, the gentle hum of pink noise has become a nightly ritual, a readily available soundscape promising deeper, more restorative sleep. However, emerging research suggests this popular sleep aid may not be the panacea it’s often portrayed as, and could even interfere with crucial sleep processes.
A recently published study in the journal Sleep indicates that exposure to pink noise during sleep can reduce the amount of time spent in REM (rapid eye movement) sleep – the stage of sleep vital for memory consolidation, emotional regulation, and learning. The study, conducted by researchers at the University of Pennsylvania, involved 25 healthy adults monitored over seven consecutive nights in a sleep laboratory.
“The negative consequences of the pink noise far outweigh the positive ones that we saw,” stated Dr. Mathias Basner, professor of psychiatry at the University of Pennsylvania and lead author of the study.
Understanding Pink Noise and Its Rise in Popularity
Pink noise is categorized as a “broadband noise,” meaning it encompasses a wide range of frequencies. It differs from white noise, which plays all frequencies at equal intensity. Pink noise emphasizes lower frequencies, creating a sound often likened to the steady rhythm of rainfall or ocean waves. While initially explored for potential benefits in areas like memory and sleep, research findings have been mixed.
The appeal of these types of background noise lies in their ability to mask unwanted sounds, a particularly attractive quality in today’s increasingly noisy environments. Since the introduction of the first white noise machine in the 1960s, a proliferation of variations has emerged. Today, lengthy pink noise recordings on platforms like YouTube garner millions of views, reflecting its widespread adoption as a sleep aid.
“So many people are using it, and it’s really indiscriminate use,” Dr. Basner observed, highlighting the prevalence of its use without a full understanding of its potential effects.
The University of Pennsylvania Study: A Controlled Examination
Driven by his observation of pink noise’s growing popularity as a sleep aid, Dr. Basner initiated a rigorous study to assess its impact on sleep quality. He noted that previous research in this area often suffered from methodological limitations, such as small sample sizes and subjective assessments.
To address these shortcomings, Dr. Basner and his team conducted their research within the highly controlled environment of a sleep laboratory at the Hospital of the University of Pennsylvania. Participants were monitored using polysomnography, a comprehensive test that measures brain waves, eye movements, and muscle tone, allowing for precise differentiation between sleep stages.
The study involved exposing participants to various conditions: no noise, environmental noise alone, pink noise alone, a combination of pink noise and environmental noise, or environmental noise paired with earplugs. Environmental noise ranged from traffic sounds to the simulated impact of sonic booms.
Over seven nights, the 25 participants (18 women and seven men) were given an eight-hour sleep window each night, with lights out at 11 p.m. And lights on at 7 a.m.
The findings revealed that exposure to environmental noise led to a decrease of 23.4 minutes in stage 3 sleep, also known as deep sleep. This stage is crucial for physical recovery, immune function, and memory consolidation. More concerningly, pink noise was associated with an average reduction of 18.6 minutes in REM sleep.
“REM sleep is extremely important for a lot of things like memory consolidation, emotion regulation, brain plasticity, and neurodevelopment,” Dr. Basner explained, underscoring the significance of this finding.
Implications for Infants and Adults
While the study focused on adults, Dr. Basner cautioned that the implications could be particularly relevant for infants. Babies spend approximately half of their sleep time in REM sleep, compared to about a quarter for adults. Exposure to pink noise during infancy could potentially disrupt critical brain development.
Based on these findings, Dr. Basner advises against using broadband noise machines in the bedrooms of newborns. For adults who choose to continue using pink noise, he recommends utilizing the lowest possible volume and setting a timer to ensure it automatically turns off.
However, he suggests that foam earplugs offer a more effective solution for blocking out unwanted noise. In the study, earplugs, when used in conjunction with environmental noise, recovered 72% of the deep sleep time that had been lost. Their effectiveness diminished at higher noise levels, around 65 decibels.
“You didn’t get the REM sleep reduction because they didn’t play anything back,” Dr. Basner noted.
Study Limitations and Future Research
The researchers acknowledge certain limitations of their study. The sample size was relatively small and comprised primarily of younger, healthy individuals without pre-existing sleep disorders or hearing loss. The study was conducted in a laboratory setting, which may not fully replicate real-world sleep environments.
The study also examined only the short-term effects of pink noise. Future research should investigate the long-term consequences of exposure, as well as explore the effects of other types of broadband noise.
“We need to do the proper research to make sure that This proves actually, at least, not harmful,” Dr. Basner concluded, emphasizing the need for continued investigation into the effects of ambient noise on sleep health.
