Snoring noise pollution—the need for objective quantification of annoyance, regulatory guidelines and mandatory therapy for snoring

Management of primary snoring in adults: A scoping review examining interventions, outcomes and instruments used to assess clinical effects

While various treatment options for primary snoring are available, evidence-based recommendations to determine the optimal intervention remain unestablished. To inform future directions of research to guide clinical decision-making, this scoping review was conducted to map the existing evidence on interventions for primary snoring, the outcomes and instruments used to assess their clinical effects in adults. The feasibility of conducting further systematic reviews and comparing outcomes across these therapies using network meta-analysis was also assessed. Of the 1673 records identified, 38 interventional studies met the inclusion criteria with three-fifths of them being before-after studies. The most common reason for study exclusion was results being reported for patients with primary snoring and obstructive sleep apnoea (OSA) combined. Interventions were surgical (73 %), behavioural and the use of devices/medications. Twenty-six common outcomes were identified and categorised into six domains. Fifty-nine instruments were used to assess the outcomes and based mainly on non-validated questionnaires. Our findings indicated (1) the need for randomised controlled trials with strict discrimination between patients with primary snoring and OSA, (2) further network meta-analyses using some outcomes is feasible, and (3) a core outcome set to inform standardised reporting for future research should be developed.

Are annoyance scores based on sound pressure levels suitable for snoring assessment in the home environment?

Purpose

An objective statement about the annoyance of snoring can be made with the Psychoacoustic Snore Score (PSS). The PSS was developed based on subjective assessments and is strongly influenced by observed sound pressure levels. Robustness against day-to-day interfering noises is a fundamental requirement for use at home. This study investigated whether or not the PSS is suitable for use in the home environment.

Methods

Thirty-six interfering noises, which commonly occur at night, were played in the acoustic laboratory in parallel with 5 snoring sounds. The interfering noises were each presented at sound pressure levels ranging from 25 to 55 dB(A), resulting in 3255 distinct recordings. Annoyance was then assessed using the PSS.

Results

In the case of minimally annoying snoring sounds, interfering noises with a sound pressure level of 25 dB(A) caused significant PSS changes from 40 to 55 dB(A) for annoying snoring sounds. If the interfering noise was another snoring sound, the PSS was more robust depending on the sound pressure level of the interfering noise up to 10 dB(A). Steady (no-peak) interfering noises influenced the PSS more strongly than peak noises.

Conclusions

The PSS is significantly distorted by quiet interfering noises. Its meaningfulness therefore depends strongly on the acoustic environment. It may therefore be assumed that scores dependent on sound pressure level are suitable for measurements when there is minimal ambient noise, as in the sleep laboratory. However, for measurements where noise is incalculable, as in the home environment, interfering noises may distort the results.

Snoring: is a reliable assessment possible?

Purpose

It is not easy to assess how severe and annoying a patient’s snoring is. Solid parameters are lacking; snorers cannot deliver a reliable self-assessment and it is uncertain whether bed partners’ statements can be relied upon. The purpose of the present study was therefore to investigate whether and how well snoring assessment based on acoustic parameters and bed partners’ reporting agree.

Methods

In a double-blind, placebo-controlled study on snoring treatment, several acoustic parameters [snoring index (SI), percentage snoring time (ST), sound pressure level, sound energy, loudness, psychoacoustic annoyance and psychoacoustic snore score (PSS)] were measured in 18 subjects during 24 polysomnographies. Bed partners also assessed snoring annoyance and loudness as well as treatment outcome.

Results

No correlation was found between the subjective annoyance caused by snoring and the acoustic parameters. Regarding perceived loudness, there was a moderate, significant correlation with loudness (N₅) and PSS over the hour with the highest SI. SI, ST, LAeq and maximum sound pressure level dB(A)_max showed no significant correlation. After the intervention only mean sound energy LAeq over the entire night showed a significant correlation (r_s = 0.782; p = 0.022) with bed partners’ assessments. However, this result was not confirmed in the second control night.

Conclusions

The non-existent or only weak correlation between bed partners’ ratings and objective parameters indicate that snoring severity should be evaluated with caution. Neither acoustic parameters, at least for one measurement over just one night, nor bed partners’ ratings should be used as the sole basis for snoring assessment.

Systematic review of the different aspects of primary snoring

Primary snoring, also known as simple or non-apnoeic snoring, is regarded as the first stage of sleep disordered breathing without severe medical consequences for the snorer and co-sleeper. Although it is a highly prevalent phenomenon in the general population, our knowledge is limited because of the lack of a consensus on terminology. This systematic review of the aspects used in the definitions of simple/primary snoring was conducted to obtain an inventory of current practices and compare these definitions with the conceptual definition of the American Academy of Sleep Medicine. PubMed and Web of Science were searched from July 2016 onwards without any language limitations, and 362 references were obtained. After selection based on titles, 39 remained, among which 29 contained a definition or reference to a definition. In 69% of the studies, a cut-off <5 apnoea/Hypopnoea events per hour of sleep on the Apnoea-Hypopnoea Index was used. Despite this tendency, the cut-offs ranged from 0 to <15/h. Unfortunately, the cut-off and occasional requirements did not match the conceptual definition of the American Academy of Sleep Medicine. A consensus must be reached on an operational and clinically relevant definition based on the clear conceptual definition.

Numerical study of dynamic glottis and tidal breathing on respiratory sounds in a human upper airway model

BACKGROUND

Human snores are caused by vibrating anatomical structures in the upper airway. The glottis is a highly variable structure and a critical organ regulating inhaled flows. However, the effects of the glottis motion on airflow and breathing sound are not well understood, while static glottises have been implemented in most previous in silico studies. The objective of this study is to develop a computational acoustic model of human airways with a dynamic glottis and quantify the effects of glottis motion and tidal breathing on airflow and sound generation.

METHODS

Large eddy simulation and FW-H models were adopted to compute airflows and respiratory sounds in an image-based mouth-lung model. User-defined functions were developed that governed the glottis kinematics. Varying breathing scenarios (static vs. dynamic glottis; constant vs. sinusoidal inhalations) were simulated to understand the effects of glottis motion and inhalation pattern on sound generation. Pressure distributions were measured in airway casts with different glottal openings for model validation purpose.

RESULTS

Significant flow fluctuations were predicted in the upper airways at peak inhalation rates or during glottal constriction. The inhalation speed through the glottis was the predominating factor in the sound generation while the transient effects were less important. For all frequencies considered (20-2500 Hz), the static glottis substantially underestimated the intensity of the generated sounds, which was most pronounced in the range of 100-500 Hz. Adopting an equivalent steady flow rather than a tidal breathing further underestimated the sound intensity. An increase of 25 dB in average was observed for the life condition (sine-dynamic) compared to the idealized condition (constant-rigid) for the broadband frequencies, with the largest increase of approximately 40 dB at the frequency around 250 Hz.

CONCLUSION

Results show that a severely narrowing glottis during inhalation, as well as flow fluctuations in the downstream trachea, can generate audible sound levels.

The Efficacy of Low-Level Continuous Positive Airway Pressure for the Treatment of Snoring

STUDY OBJECTIVES

To assess effects of low-level continuous positive airway pressure (CPAP) on snoring in habitual snorers without obstructive sleep apnea (OSA).

METHODS

A multicenter prospective in-laboratory reversal crossover intervention trial was conducted between September 2013 and August 2014. Habitual snorers were included if they snored (inspiratory sound pressure level ≥ 40 dBA) for ≥ 30% all sleep breaths on a baseline sleep study (Night 1), and if significant OSA and daytime somnolence were absent. Included participants then underwent a CPAP titration study at 2, 4, or 6 cm H₂O (Night 2) to examine snoring responses to step-increases in nasal pressure, a treatment night at optimal pressure (Night 3), followed by baseline night (Night 4). At each pressure, snoring intensity was measured on each breath. Snoring frequency was quantified as a percentage of sleep breaths at thresholds of 40, 45, 50, and 55 dBA. Sleep architecture and OSA severity were characterized using standard measurements.

RESULTS

On baseline sleep studies, participants demonstrated snoring at ≥ 40 dBA on 53 ± 3% and ≥ 45 dBA on 35 ± 4% of breaths. Snoring frequency decreased progressively as nasal pressure increased from 0 to 4 cm H₂O at each threshold, and plateaued thereafter. CPAP decreased snoring frequency by 67% and 85% at 40 and 45 dBA, respectively. Intervention did not alter sleep architecture and sleep apnea decreased minimally.

CONCLUSIONS

Low-level CPAP below the range required to treat OSA diminished nocturnal snoring, and produced uniform reduction in nightly noise production below the World Health Organization's limit of 45 dBA.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, identifier: NCT01949584.

Acoustic analysis of overnight consecutive snoring sounds by sound pressure levels

CONCLUSION

The sound pressure level (SPL) parameters, especially the A-weighted equivalent sound level (LAeq) and accumulative percentile sound level 10 (L10), were significantly different between simple snoring (SS) and obstructive sleep apnea-hypopnea syndrome (OSAHS). The apnea-hypopnea index (AHI) was the most significant factor to affect the SPLs of snoring sounds. LAeq and L10 were valuable acoustic characters of snoring which could reflect the severity of sleep disordered breathing in clinic.

OBJECTIVES

Due to the limitation of acoustic analysis of single snoring sound for snorers, this study analyzed characteristics of consecutive snoring sounds overnight by the SPLs in patients of SS and OSAHS.

METHOD

Ninety-four patients who underwent simultaneous SPL recording and polysomnography (PSG) were included in this study. Parameters of SPL such as LAeq, peak sound level (Lpeak), L10, L50, and L90 were analyzed. The correlation between these parameters and PSG results was also analyzed.

RESULTS

The LAeq and L10 in OSAHS patients were significantly different from patients with SS. The body mass index (BMI) was positively correlated to LAeq and L10. Among various factors of PSG data and demographic factors, the SPLs were mostly affected by the AHI and the lowest oxygen saturation (LSaO2).

Association between housing quality and individual health characteristics on sleep quality among Latino farmworkers

Although poor sleep quality and associated sleep disorders are associated with increased risk of job injury and multiple mental and physical health problems, scant research has examined sleep quality among Latino farmworkers. Interviews were conducted with 371 male Latino farmworkers working in North Carolina during the 2010 agricultural season. Data on housing quality and sleep quality were collected. Access to air conditioning was significantly and positively associated with good sleep quality. This association remained when other housing characteristics and individual health indicators were controlled. Good sleep quality was associated with low levels of pain, depression, and anxiety. Poor sleep quality among Latino farmworkers was associated with poorer indicators of health. One important indicator of housing quality, air conditioning, was associated with better sleep quality. Further research is required to delineate how to improve the adequacy of farmworker housing to improve sleep quality and other health indicators.

Reliability of home-based physiological sleep measurements in snoring and non-snoring 3-year olds

PURPOSE

To study snoring and non-snoring 3-year olds in their own homes and to establish reference values and night-to-night variability of physiological measurements taken during sleep.

METHODS

One hundred and sixty-six children, aged 3.2-4.0 years, identified as at high (n = 83, M/F = 1.5:1) or low (n = 83, M/F = 1.4:1) risk for persistent snoring, as rated by a parent, wore a sleep screening system (Grey Flash) for up to five consecutive nights, to measure snoring, oxygen saturation, heart rate, movement, sleep efficiency, and sleep timing.

RESULTS

The snoring group snored 25% of their total sleep time, while the non-snoring group snored just 7.6%. Reliability estimates were calculated, using intraclass correlations to establish the reliability of single recordings and the Spearman-Brown prophecy formula to estimate reliability over multiple recordings. Snoring (percent), turn index (number of turns per hour), and mean heart rate were adequately assessed in both groups with one recording night (all intraclass correlation coefficients (ICCs) ≥0.70). Furthermore, mean SpO(2) was measured with sufficient reliability with two recordings in non-snorers (ICC = 0.71), while five recording nights were necessary to reach reliability in snorers (ICC = 0.71). SpO(2) nadir did not reach adequate reliability in either group even after seven recording nights.

CONCLUSIONS

Our results showed that snoring can be measured reliably at home with just one recording night, whereas most other physiological sleep measures require two or more recordings.

The acoustics of snoring

Snoring is a prevalent disorder affecting 20-40% of the general population. The mechanism of snoring is vibration of anatomical structures in the pharyngeal airway. Flutter of the soft palate accounts for the harsh aspect of the snoring sound. Natural or drug-induced sleep is required for its appearance. Snoring is subject to many influences such as body position, sleep stage, route of breathing and the presence or absence of sleep-disordered breathing. Its presentation may be variable within or between nights. While snoring is generally perceived as a social nuisance, rating of its noisiness is subjective and, therefore, inconsistent. Objective assessment of snoring is important to evaluate the effect of treatment interventions. Moreover, snoring carries information relating to the site and degree of obstruction of the upper airway. If evidence for monolevel snoring at the site of the soft palate is provided, the patient may benefit from palatal surgery. These considerations have inspired researchers to scrutinize the acoustic characteristics of snoring events. Similarly to speech, snoring is produced in the vocal tract. Because of this analogy, existing techniques for speech analysis have been applied to evaluate snoring sounds. It appears that the pitch of the snoring sound is in the low-frequency range (<500 Hz) and corresponds to a fundamental frequency with associated harmonics. The pitch of snoring is determined by vibration of the soft palate, while nonpalatal snoring is more 'noise-like', and has scattered energy content in the higher spectral sub-bands (>500 Hz). To evaluate acoustic properties of snoring, sleep nasendoscopy is often performed. Recent evidence suggests that the acoustic quality of snoring is markedly different in drug-induced sleep as compared with natural sleep. Most often, palatal surgery alters sound characteristics of snoring, but is no cure for this disorder. It is uncertain whether the perceived improvement after palatal surgery, as judged by the bed partner, is due to an altered sound spectrum. Whether some acoustic aspects of snoring, such as changes in pitch, have predictive value for the presence of obstructive sleep apnea is at present not sufficiently substantiated.