STUDY PROTOCOL article
Front. Neurol., 26 January 2023 Sec. Sleep Disorders Volume 14 - 2023 | https://doi.org/10.3389/fneur.2023.1024726
Study protocol to support the development of an all-night binaural beat frequency audio program to entrain sleep
Gantt Clinical Research Institute LLC, Orlando, FL, United States
Background: Given that the stages of sleep have specific brainwave patterns, it may be feasible to manipulate brainwaves to induce stages of sleep to improve better sleep quality. Binaural beat frequencies (BBFs) are an auditory-neurologic technique that uses auditory tones via headphones to manipulate brainwave activity in turn affecting the listener's state of consciousness. However, BBFs are often sold in only one frequency which may not allow the listener to transition through the phases of sleep. This study is Phase 2 of a four-phase feasibility study to assess if systematically sequencing a variety of BBFs can improve sleep efficiency.
Methods: This protocol uses a two cohort unblinded and double-blinded, randomized, pre- and post-intervention methods and crossover matched group design. In Cohort 1, a sample of 106 participants with poor sleep quality will be randomized into two groups. All participants will start with 1 week of no intervention. Group 1 will use theta/delta BBF for 2 weeks followed by 1 week of no intervention followed by music for 2 weeks. Group 2 will do the reverse. In Cohort 2, 62 participants will be blinded and randomized into two groups. Group 3 will use music for 2 weeks followed by a 1-week break followed by music embedded with theta/delta BBF for 2 weeks. Group 4 will do the reverse. Using Cohort 1 music only as a control, data will be collected using sleep actigraphy, sleep quality questionnaires, and sleep diaries with a crossover and match group analysis between cohorts to compare the effect of no intervention vs. music vs. BBF only vs. music with BBF on sleep quality. Discussion: Phase 1 concluded that theta BBF was able to decrease stress to help induce sleep. Phase 2 will assess if theta and delta BBFs, with breaks to allow for REM, will be able to sustain sleep to improve sleep efficiency. The data from Phase 1 and 2 will provide information to help construct an all-night audio program with the appropriate BBF and timing to trigger the correct sleep stage for better sleep efficiency. If this concept is feasible, it could be beneficial for many sleep disorders.
Introduction Sleep quality Sleep is essential as it has a multifaceted connection to health and chronic disease. Due to the rising societal impact of sleep deficiencies and circadian dysfunctions, more research is needed on new strategies to improve sleep quality to support physiological function, behavioral health, and wellbeing throughout the lifespan (1). When adequate sleep is not attained it can negatively affect vigilance, reaction time, learning ability, alertness, mood, hand-eye coordination, and memory (2). In the workplace, it reduces efficiency and productivity, underestimates performance capabilities, and increased errors which can cause accidents (3). According to the 2021 National Sleep Foundation statistics, between 10 and 30% of adults struggle with sleep with 35% reporting sleeping <7 h per night on average with half of all Americans stating that they feel sleepy during the day ~3–7 times a week (4). Given these statistics, over half of adults believe that if they had better sleep, they would be more effective which would positively affect their quality of life (4). Over the years, studies have assessed a variety of evidence-based strategies to mitigate poor sleep quality such as good sleep hygiene, strategic napping, appropriately timed rest breaks, optimal lighting, and pharmacologic (5). However, with all of these strategies poor quality sleep still remains an issue. The use of auditory stimuli to improve sleep The use of auditory stimuli, such as white noise, pink noise, and music, has shown efficacy in improving sleep quality in a variety of populations and settings. In a systematic review published in 2022, the results showed that of 34 studies, 19 studies [6 using white noise (33%), 9 using pink noise (81.9%), and 4 using multi-audio (66.7%)] reported positive effects on improving sleep quality with multi-audio having the lowest risk of bias (mean/standard deviation: 1.67/0.82) compared to white noise (2.38/0.69) and pink noise (2.36/0.81) (6). Another interesting auditory stimulus that has evolved over the last few years is the use of 432 Hz music which is widely used in the New Age genre. This process is done by slowing down (by 32 hundredths of a tone) the execution of a song originally tuned at 440 Hz, using music editing software (7). It is theorized that music played at 440 Hz, which is the current frequency used for tuning musical instruments, has a different psychological and/or physiologic effect than that same music played at 432 Hz (8). In a study published in 2020, 12 spinal injury patients were subjected to their favorite music tuned to 440 Hz or 432 Hz for 30 min each day for two periods (8). Those who listened to music at 432 Hz showed a significant improvement in sleep scores (+3.6, p = 0.02) when compared to those listening to music at 440 Hz (−1.50, p = 0.34) (8). Another novel auditory stimulus that has been shown to improve sleep quality is the concept known as binaural beat frequencies (BBFs). Binaural beats frequencies The concept of BBF was first discovered by German researcher Heinrich Wilhelm Dove in 1839 (9). This phenomenon occurs when a frequency is played to one ear and a slightly different frequency is played to the other giving the perception of the presence of a third frequency (the difference between the two frequencies) (9) (Figure 1). This third frequency does not reflect a physical property of sound but is generated at the convergence of neural activity from the two ears in the central binaural auditory pathways of the brain (10). This frequency then causes the brainwaves to fall in sync with the frequency in turn altering the listener's state of consciousness (10). “The most widely accepted physiological explanation for this suggests that discharges of neurons that preserve phase information of the sound in each ear according to the volley principle converge on binaurally-activated neurons in the ascending auditory pathway that, in turn, generate brainwaves to fall in sync with the frequency” [(10), p. 1,514–1,515]. Since brainwave frequencies fall into five major categories (e.g., gamma, beta, alpha, theta, and delta) with each producing five distinct levels of states of consciousness, one only has to adjust the sound frequencies to each ear to produce the state of consciousness he/she desires.
Figure 1. Concept of Binaural beats. Image courtesy of Patrick Alban, DC and Deane Alban. https://bebrainfit.com/binaural-beats-meditation.
Binaural beat frequencies can be constructed using easily accessible audio equipment and software as evidence by the many audio files found on Spotify, YouTube, Apple Music and the Apple app store. However, BBFs are often sold in only one frequency which may not allow the listener to transition through the phases of sleep. Given that commonly used public health web sites are writing about the benefits of BBFs, it is imperative to conduct more research not only for its efficacy but for public safety. According to the National Library of Medicine National Center for Biotechnology Information's database, since 2014 there has been a rise in the number of research studies assessing the efficacy of BBFs due to interest in its potential. Studies have been conducted for its efficacy on attention (11), anxiety (12–14), cognition (15), mood (16), depressive disorders (17), stress (18, 19), with music therapy (20), memory (21–23), pain (24, 25), and even for post-deployment stress in the United States military (26).
The efficacy of using binaural beats frequencies for sleep quality
Although there is a rise in BBFs studies, there are only a handful of published studies assessing the use of BBF for sleep. In a pilot study published in 2013, 15 elite German league soccer players used BBF for 8 weeks to improve sleep quality in hopes to improve performance (27). Once a week participants completed a sleep diary, an adjective list for psychophysical and motivational states, and a self-assessment questionnaire for sleep and awakening quality (27). When compared to a control group there was improved perceived sleep quality and the post-sleep state, however there was no effect on performance which the investigators believed would have required longer exposure to the intervention (27). In a 2017–2018 study, 43 participants with insomnia were exposed to theta BBF and measured using spectral analysis of the quantitative electroencephalography data. When music embedded with theta BBF was played, the relative theta power increased in the occipital lobe (p = 0.009) (28). After listening to music with BBF for 2 weeks, the decrease in the beta power from baseline was more prominent than after listening to music without BBF (28). In a study published in 2018, 24 participants were monitored for three consecutive nights (adaptation night, baseline night, and an experimental night) (29). On the experimental night participants were exposed to a 3-Hz BBF on 250-Hz carrier tone (29). While utilizing electroencephalograms, electro-oculograms, and electromyograms, the intervention was initiated when the first epoch of N2 was detected and was stopped when the first epoch of N3 sleep was detected (29). When compared to a control group it showed that the N3 sleep duration was longer and N2 sleep was shorter and did not disturb sleep continuity indicated by arousal index and WASO without sleep fragmentation induction (29). In a 2022 pilot study, 20 students were exposed to 90 min of delta BBF every day for 1 week. When compared to 1 week of baseline, sleep diary and the Profile of Mood State questionnaire showed that the average duration of sleep latency and the number of awakenings were significantly shorter (p < 0.001) (30). The mean duration of actual night sleep and waking time in the morning was significantly longer (p < 0.001) with the majority of the participants (70%) describing their sleep quality as good to excellent (30).
It is also important to review studies that did not show a significant difference as there may be more information to further investigate or an opportunity to replicate. For example, in a double-blind sham-controlled randomized trial published in 2020, 43 participants with subclinical insomnia were divided into two groups, one using BBF and the other using a sham audio (31). Although the effect was much stronger for the group that used music with the BBF (Cohen d = 1.02 vs. 0.58), the insomnia severity decreased in both groups without significant difference (p = 0.656) (31). In reviewing the awake electroencephalographic analysis, the relative beta power was higher in the group that used music with the BBF (0.2 ± 7.02 vs. −3.91 ± 6.97, p = 0.041) (31). Taking a closer look at this study, although both groups had a decrease in insomnia, the group that used music with BBF had a higher beta power the next day. It could be possible that using BBF while asleep made the listeners more alert the next day, hence the higher beta power. Another item noted in many of the studies was that only one BBF frequency was used, whereas normal sleep is comprised of transitioning through a variety of brainwave frequencies. Since there is no evidence to support or to reject if using theta BBF (light sleep) alone all night will produce the same or better sleep efficiency than if using it in combination with delta BBF (deep sleep), more studies using multiple BBFs should be conducted.
Using an ideal hypnogram as a model to construct an all-night BBF audio program
Studies that have compared hypnograms of healthy adults have formulated some key similarities that can be used as a model of a good night sleep (Figure 2). Although each individual has a variety of factors that make their sleep experience different, using a model of a healthy adult can serve as a starting point that can later be adjusted for the individual. Since the various stages of sleep have signature brainwave frequencies and that BBFs have shown to be able to affect brainwaves, it could be possible to systematically arrange BBFs in an order to reflect a normal sleep cycle and embed them onto a 6-, 7-, or 8-h audio track to entrain an entire night of sleep. Given that poor sleep quality can stem from not being able to fall asleep, stay asleep, or awakening at the wrong time; conducting a series of feasibility studies to address each issue separately can provide data to support the creation of customizable all-night BBF audio programs (Table 1).