Men vs. Women - Who Snores More?

Men vs. Women – Who Snores More?

About Snoring, Science | Oct 25, 2019
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Do men snore more than women? The short answer to this question is yes. There are sex differences when it comes to snoring. But there’s a little bit more to it than that.

Type “snoring” into a search engine and click on images. What do you see? Nine of the fifteen pictures on my screen showed men with mouths wide open whilst unfortunate women wrenched pillows over their ears to block out the sound. It’s a cliché, but one that is based on some truth.

Twice as many men snore than women, with roughly 40% of men reporting snoring versus 20% of women. That still means that 840 million women are regular snorers. Snoring is certainly not just a male problem, but there are differences. Let’s explore why and how.

Men’s airways are primed for snoring

The reason more men snore is partly down to their airway anatomy. Studies have found that there are crucial differences in the structure of men’s airways.

More soft tissue

Firstly, there’s more tissue in the noise makers themselves. Studies indicate that the male soft palate – a key player in generating snoring sounds – has a larger cross-sectional area. There’s basically more tissue available to flap around and make noise [1].

Male upper airway collapses more

Secondly, men’s upper airways are more prone to obstruction. The vulnerable area between the hard palate and epiglottis is larger in men. This means there is a greater amount of unsupported soft tissue that will relax whilst asleep [2].

Side note:

It is important to note that this has nothing to do with men having deeper voices. Whilst men’s vocal folds are indeed longer, they have more structural support and reside lower than the collapsible area associated with snoring. The area below the roof of your mouth and above the epiglottis is the soft, flappy area we are interested in.

Men gain fat on the neck

Finally, men put weight on the areas that can cause snoring. The chance of your airway collapsing is increased if there is more weight on your neck. An increased neck size and fat around the neck therefore puts you at greater risk of snoring.

We know that obesity is a great risk factor in snoring, but men and women distribute fat differently which influences snoring patterns. Men put on more weight around their neck and chest, whereas women tend to gain fat on their thighs, hips and buttocks.

Snoring is linked to male hormones

Testosterone is the main male sex hormone. Its primary duty is the maintenance and development of reproductive tissue, but it also plays a part in snoring.

Side note: what are hormones?

Hormones are produced in various glands and are the body’s chemical messengers. They travel in the blood and are a means of communication between different areas of the body, regulating the inner workings of cells.

Various studies have looked into the effects of testosterone on breathing during sleep, with a focus on sleep apnea. It has been linked to increased airway collapsibility and greater breathing instability, though the exact mechanism is still uncertain [3].

Indeed, raised testosterone in women is linked to disturbed breathing during sleep. Women with polycystic ovarian syndrome, a condition where testosterone levels are higher than they should be in women, have a greater risk of developing obstructive sleep apnea [4].

Female hormones protect from snoring

Whilst male sex hormones increase the chance of snoring, female sex hormones have a protective effect.

Steady ventilation

Progesterone, a hormone particularly high during pregnancy, promotes steady ventilation. This causes a less pronounced drop in airflow during sleep and makes the soft airway less prone to collapse [5].

Less relaxed tongue

Progesterone, alongside another key female hormone, estrogen, enhances the ability of a key muscle in the tongue to contract, reducing the likelihood of it falling back and causing a blockage [6].

Menopause increases the likelihood of snoring

As female sex hormones decline rapidly at the menopause, the likelihood of developing snoring or sleep apnea increases.

Incidence of snoring increases with age for both sexes, but in women, the onset of the menopause is a watershed moment when it comes to snoring and sleep apnea.

Artificially re-introducing female sex hormones via hormone replacement therapy (HRT) has been shown to reduce the occurrence of sleep apnea [4].

Obstructive Sleep Apnea is different between men and women

Sleep apnea is less common than habitual snoring but the relative proportions of men and women are roughly the same, with twice as many men suffering from the condition as women. However, eight times more men are diagnosed [7].

Some time ago, the sleep apnea ratio of men to women was thought to be as stark as 60:1. We are learning now that this is because of frequent misdiagnosis and the fact that women often exhibit an atypical form of the condition.

The severity of sleep apnea is measured by counting the number of instances where breathing stops (apnea) or is severely reduced (hypopnea). This measurement is called the apnea-hypopnea index (AHI). As women are less likely to experience complete airway collapse, they tend to have a lower AHI score.

Importantly, these women aren’t necessarily experiencing less obstruction. Women display more frequent episodes of longer, partial obstruction that still causes the fatigue, sleepiness and health issues associated with OSA.

Conclusion

With snoring, as with many dysfunctions in the body, there are things that are out of our control. Our sex is obviously the main one. Seeing where you fit into the profile of the 2 billion people worldwide who snore can help you understand your snoring better and be ready to take the next steps.

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References

  1. Lin CM, et al. Gender Differences in Obstructive Sleep Apnea and Treatment Implications. Sleep Medicine Reviews 2008; 12(6): 481-496. https://www.ncbi.nlm.nih.gov/pubmed/18951050
  2. Malhotra A, et al. The Male Predisposition to Pharyngeal Collapse: Importance of Airway Length. American Journal of Respiratory and Critical Care Medicine 2002; 155(10): 1388-1395. https://www.ncbi.nlm.nih.gov/pubmed/12421747
  3. Andersen ML & Tufik S. The effects of testosterone of sleep and sleep-disordered breathing in men: Its bidirectional interaction with erectile function. Sleep Medicine Reviews 2008; 12: 365-379. https://doi.org/10.1016/j.smrv.2007.12.003
  4. Bixler EO, et al. Prevalence of Sleep-disordered Breathing in Women: Effects of Gender. American Journal of Respiratory and Critical Care Medicine 2001; 163(3): 608-613. https://doi.org/10.1164/ajrccm.163.3.9911064
  5. Saaresranta T, et al. Sleep disordered breathing: is it different for females? European Respiratory Journal, Open Research 2015; 1(2): 00063-2015. https://dx.doi.org/10.1183%2F23120541.00063-2015
  6. Popovic RM & White DP. Upper airway muscle activity in normal women: influence of hormonal status. Journal of Applied Physiology 1998; 84: 1055-1062. https://doi.org/10.1152/jappl.1998.84.3.1055
  7. Hines J. 2018. Women with Sleep Apnea: Why Women are Less Often Diagnosed with OSA. [ONLINE] Available at: http://www.alaskasleep.com/blog/women-with-sleep-apnea-why-women-are-less-often-diagnosed-with-osa [Accessed 16 August 2018].


Is Snoring Genetic?

Is Snoring Genetic?

Science | 23 Oct, 2019
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Is snoring genetic? Questions in life rarely have a definitive answer, and this is no exception. Here, the answer is an unsatisfying “yes and no”. There is a genetic connection, but not a direct cause.

Your DNA can increase the risk of snoring but won’t condemn you to a certain life of nocturnal noises.

My family snores. Am I doomed?

Multiple studies have found that coming from a family of snorers confers a 3-fold increased risk of snoring yourself [1]. This is due to a number of different inherited features but there is no such thing as a “snoring gene”.

There is also some research to suggest that an increased risk of obstructive sleep apnea can be inherited [2].

But fear not – if your whole family snores, whilst you may have to work a little harder to make sure that you don’t, you are far from doomed!

What heritable traits can make you snore?

Cranio-facial features

A predisposition for snoring can come from certain structural features in your face and airways.

Physical characteristics like your eye colour, height and skin tone are inherited from your parents. The same is true of the features that can make you snore.

The usual anatomical culprits for snoring are:

  • Small nostrils
  • Receded chin (known as retrognathia)
  • Small jaw (known as micrognathia)
  • Narrow airway
  • Large tongue
  • Large soft palate

All of these factors decrease the size of your airway and disrupt airflow therefore making snoring more likely.

If your snoring can be attributed to a distinct anatomical feature, it can usually be helped with standard anti-snoring remedies. Sometimes, if the abnormality is particularly pronounced, corrective surgery could be a solution.

Weight

scales showing overweight

Obesity is a key risk factor in snoring and obstructive sleep apnea.

Basically, the heavier you are, the more likely you are to snore.

Less clear is how much your genes are to blame. In some cases, yes, being overweight does seem to run in families, but it is the subject of much debate as to whether this is the result of nature or nurture.

The likely answer is, again, probably somewhere in the middle …

Physiological factors that dictate weight can indeed be inherited genetically. Appetite is regulated by a system of hormones and signals in the body which are ultimately controlled by a series of underlying genes.

On the other hand, attitudes to food, diet and weight are learned from the behaviours and views of the people around us. This can include our family or simply the society and culture we live in.

Conclusion

There are lots of factors that influence snoring, and it would appear that your DNA is one of them. It’s important to remember that this is only an influence and not a sentence to an eternity of snoring.

So if your mum and dad compete for the best (or worst) Snore Score, you need not worry. You can’t control your genes, but you can control a lot of other factors that contribute to your snoring. Try to understand your triggers and the solutions that work for you.

If you don’t know where to start, have a look at SnoreLab’s 7 recommended lifestyle factors that can make huge differences to your snoring.

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References

  1. Jennum P, et al. Snoring, family history, and genetic markers in men. The Copenhagen Male Study. Chest 1995; 107(5): 1289-1293. https://www.ncbi.nlm.nih.gov/pubmed/7750320
  2. Cade BE, et al. Genetic associations with obstructive sleep apnea traits in Hispanic/Latino Americans. American Journal of Respiratory Critical Care Medicine 2016; 194: 886–897. PMC5074655


The Science Behind SnoreGym

The Science Behind SnoreGym

Mouth Exercises, Science | Oct 20, 2019
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Researchers have found evidence to show that performing mouth exercises can reduce snoring and sleep apnea, improve deep sleep and give more rest to bed partners. SnoreGym’s exercises are based upon the routines detailed in a number of scientific papers. This post is a summary of those papers.  

Introduction

Snoring occurs when the muscles in your upper airway relax, restricting airflow which in turn causes these tissues to vibrate and make sound.

Conventional snoring remedies treat the symptom, not the cause. Whilst they may stop the sound in the short term, they don’t address the root of the problem – weak muscles in the airway.

Increasing volumes of research are highlighting that snorers don’t need to be committed to a snoring remedy that they switch on or wear for the rest of their lives, but rather, they can incorporate inexpensive and effective techniques into their daily lives to stop snoring without artificial assistance.

Using techniques adapted from speech and language therapy, various research groups have employed the use of a set of oropharyngeal exercises which address weaknesses and develop muscular tone in the tongue, soft palate, throat, cheeks and jaw. This is with a view to reducing snoring, decreasing the severity of sleep apnea, mitigating disturbance of bed partners and producing better sleep and quality of life [1].

In this article, we summarise their findings.

Effects of Oropharyngeal Exercises on Patients with Moderate Obstructive Sleep Apnea Syndrome – Guimaraes et al, 2009 [2]

Overview of study

Kátia Guimaraes is a speech and language therapist from Brazil and is one of the first people to propose that oropharyngeal exercises can produce positive outcomes for obstructive sleep apnea [3].

This study uses an exercise regime that has become the basis for many subsequent experiments (though now, usually somewhat redacted). It is the first of its kind, has a robust design and is the most extensive.

Study design

Patients selected for the study met the following criteria:

  • Aged 25-65
  • BMI under 40
  • Previous diagnosis of moderate obstructive sleep apnea (AHI 15-30) via a sleep study

Guimaraes and colleagues designed a randomised-controlled trial. This means that as well as getting some patients to perform the prescribed exercises under scrutiny, another group of patients were given “sham therapy” and nasal irrigation as a control. The sham therapy consisted of simple deep breathing exercises and had to be performed with the same frequency as the study group’s exercises. This is a similar concept to a placebo in a drug trial.

The study group

The study group of sixteen patients were given a set of exercises designed to work out a variety of muscles. These exercises included:

  • Tongue brushing
  • Sliding tip of the tongue back along hard palate
  • Sucking tongue against roof of the mouth
  • Forcing tongue down into the floor of the mouth whilst the tip stays in contact with the lower front teeth
  • Pursing lips
  • Sucking movements with the cheek
  • Using cheek muscles to pull against a finger
  • Elevation of soft palate

These exercises were repeated daily including a once weekly supervised session with a speech pathologist. The duration of the study was three months.

In addition to the exercises themselves, patients also supplemented their therapy with bilateral chewing (using both sides of the mouth to chew) with a focus on correct tongue, teeth and lip positioning.

Patients in both groups underwent a sleep study before starting their treatment and again after the three months. Polysomnography was conducted by professionals blind to the group allocation of the patients.

The patients in both groups also used the Epworth Sleepiness Scale (0-24) and answered questions about perceived snoring frequency and intensity (0-4).

Results

The findings from PSG comparisons before and after are as follows:

  • There were significant decreases in the severity of sleep apnea in the study group.
  • Average AHI in the study group significantly decreased from 22.4 to 13.7 – a 39% reduction.
  • Average AHI in the control group showed a non-significant increase from 22.4 to 25.9.
  • 62.5% of study group patients shifted their severity classification from moderate obstructive sleep apnea to mild or none.
  • The lowest recorded oxygen saturations improved for the study group: 83% at baseline, 85% after 3 months.
  • The lowest recorded oxygen saturations worsened for the control group: 82% at baseline, 80% after 3 months.

In addition to the objective, quantifiable findings from PSG analysis, patients and their partners also answered a series of questionnaires about snoring frequency and intensity, and sleepiness:

  • In the study group, snoring frequency and intensity significantly decreased from 4 to 3 and 3 to 1 respectively (in the control group, there was no change in snoring frequency and intensity).
  • In the study group, the Epworth Sleepiness Scale score significantly decreased from 14±5 to 8±6 (in the control group, there was no change in sleepiness).

Effects of Oropharyngeal Exercises on Snoring – Ieto et al, 2015 [4]

Overview of study

This study looked at the influence of exercises on primary snoring as opposed to obstructive sleep apnea. The subjects were described as being “a population poorly evaluated by the scientific community […] composed of middle-aged and overweight patients who were disturbed by snoring, were on average not sleepy and did not present severe OSA”. In short, unlike much of the research into sleep-disordered breathing, this research assesses the “normal snorers”.

There are fewer exercises in this study than used by Guimaraes et al [2], and the 5 exercises used in this study form the basis of subsequent work. Importantly, this study shows that big workout sessions weren’t necessary to have a positive effect. 3 short sets of exercises every day for 3 months was shown to reduce snoring.

Study design

Patients selected for the study met the following criteria:

  • Aged 33-59
  • BMI under 40
  • Complaints of primary snoring with recent diagnosis confirming such, or of mild-moderate obstructive sleep apnea (AHI 5-30)

Ieto and her team used a control group (20 subjects) as well as a therapy group (19 subjects). Each group was randomly allocated. The study duration was 3 months.

The patients underwent polysomnography at baseline and after the 3 months to objectively measure snoring. This was done by creating a “snore index” which assessed the number of times per hour the patient broke a threshold of 38 db.

Subjects also answered questions on sleepiness using the Epworth Sleepiness Scale and sleep quality using the Pittsburgh Sleep Quality Index before and after the study.

A set of 5 exercises were performed three times a day, each session taking roughly 8 minutes):

  • Push the tip of the tongue against the hard palate and slide backwards – repeat 20 times.
  • Suck the tongue upward against the hard palate and press – repeat 20 times.
  • Force the bottom of the tongue against the floor of the mouth whilst the tip maintains contact with the lower incisors – repeat 20 times.
  • Elevate soft palate and uvula whilst saying “ah” – repeat 20 times.
  • Use cheek muscles to pull against finger – repeat 10 times on each side.

In addition to these exercises, when eating, subjects were told to alternate bilateral chewing and swallowing pushing the tongue into the hard palate.

The control group performed a “sham therapy” of deep-breathing exercises as well as wearing nasal strips during sleep and performing nasal irrigation 3 times per day.

Results

Objectively measured snoring using the snoring index did not change for the control group but showed a significant decrease in the treatment group:

  • Frequency of snoring reduced by 36%
  • Total power of snoring reduced by 59%
  • The objective snoring reduction was corroborated by a significant subjective decrease in the perception of snoring by bed partners.

Whilst not the primary focus of this study, a decrease in average AHI was also observed for the small subset of snorers (8 subjects) recently diagnosed with moderate OSA from an average AHI of 25.4 to 18.1 (a reduction of 29%).


Oropharyngeal exercises in the treatment of obstructive sleep apnoea – Verma et al, 2016 [5]

Overview of study

Another study with its primary focus on obstructive sleep apnea, this study stands out due to the findings beyond snoring, particularly on sleepiness and sleep quality.

The types of exercise in this study are more extensive and require a greater investment of time and effort.

Study design

As a case report, this study has a less robust design as it is missing a control group who don’t receive the intervention under investigation.

20 patients with mild to moderate obstructive sleep apnea (AHI 5-30) were given a rigorous set of oropharyngeal exercises. These exercises were split into 3 grades of difficulty, with patients stepping up a grade for every month of the 3 month study. Each exercise had to be repeated for 10 reps, 5 times per day.

The Epworth Sleepiness Scale, subjective snoring questionnaires and full PSG were performed at baseline and after 3 months.

Results

After the three month trial, the researchers found the following:

  • 85% of patients in the study showed a significant reduction in sleepiness.
  • Patients spent on 1.6 hours in deep sleep, compared to 0.97 at baseline – a 65% increase.
  • The average snoring as measured on the snoring intensity scale (0-4, lowest to highest) decreased significantly from 2.8 to 1.7.
  • Significantly less time was spent at oxygen saturations below 90%.

The effects of oropharyngeal-lingual exercises in patients with primary snoring – Nemati et al, 2015 [6]

Overview of study

Similar to the study conducted by Ieto et al, this study addressed the effect of exercises on primary snoring – not obstructive sleep apnea.

In addition to their explorations of the impact on snoring intensity and frequency, Nemati and colleagues also took the interesting step to look at the psychological and emotional impacts of snoring – assessing the relationship between changes in snoring intensities and conflicts had with roommates.

Study design

Interestingly, all measurements from this study were obtained from roommates of the snorer. 53 snorers were assessed before and after 3 months of soft palate, tongue and facial exercises totalling 30 minutes per day, at least 5 times per week. This was done by asking their roommates to report on the severity their snoring using a sliding scale of 0 (no snoring) to 10 (unbearable snoring).

In part due to the lack of a control group, this study describes itself as “semi-experimental”. That said, a sample size of 53 is good.

Results

Before versus after the exercise intervention:

  • Average snoring severity significantly decreased from 7.01 to 3.09 – a 56% reduction.
  • This reduction in the severity of snoring had a significant relationship the number of conflicts with roommates.

The role of oral myofunctional therapy in managing patients with mild to moderate obstructive sleep apnea – Baz et al, 2012 [7]

This prospective study evaluated the effect of oropharyngeal exercises on 30 patients with mild to moderate obstructive sleep apnea.

The exercises – similar to those outlined by Guimaraes et al [2] – were conducted in twice weekly supervised sessions plus at home for 3-5 times a day for at least 10 minutes at a time.

After the three months of therapy, patients showed some very positive, statistically significant changes:

  • 47% of patients reported not snoring any more.
  • Only 40% (compared to 100% at baseline) reported still experiencing excessive daytime sleepiness. This was reflected on the Epworth Sleepiness Scale with an average decrease from 16.4 to 9.27.
  • Average AHI reduced from 22.27 to 11.53.
  • Time spent at an oxygen saturation below 90% was halved.

Effect of speech therapy as adjunct treatment to continuous positive airway pressure on the quality of life of patients with obstructive sleep apnea – Diaferia et al, 2013 [8]

Speech and language therapy techniques underpin anti-snoring exercises. This study looked at the effectiveness of speech therapy in addition to the more conventional treatment of CPAP for obstructive sleep apnea.

In a nicely robust study design, there were four groups of similar sample sizes:

  • Speech therapy alone (n = 27)
  • Sham therapy alone (n = 24)
  • CPAP alone (n = 27)
  • Combination of CPAP with speech therapy (n = 22).

Speech therapy alone was shown to drastically reduce the average AHI for these patients (28.0 to 13.9). When supplemented with CPAP, the average reduction was even more marked, dropping from 30.4 (just over the “severe” threshold) to 3.4 (below the “mild” threshold).

In terms of sleepiness, speech therapy alone showed comparable results to using CPAP alone. The sham therapy control showed no difference in either sleepiness or AHI.


Other studies

The aforementioned studies have shown that a clearly defined set of exercises, repeated over time can produce very positive outcomes in terms of snoring reduction and reduction of sleep apnea severity amongst other facets like sleep quality and partner disturbance.

We believe this structured approach is ideal for working into your daily routine. However, the evidence extends beyond these sets of exercises.

Research groups have shown that you can work out your snoring muscles via other means. It could even be said that these earlier studies inspired the research into oropharyngeal exercises fo snoring. These techniques combat snoring via the same mechanisms as the prescribed exercises, so their findings are certainly worth a mention.

Can Singing Exercises Reduce Snoring? – Ojay and Ernst, 2000 [9]

Alise Ojay, a choir director, singer, composer and research fellow at the University of Exeter in the UK developed a series of singing exercises for a group of 20 snorers.

The group sung these songs for 20 minutes a day for three months. These songs weren’t the typical tunes you might hum to yourself, but were instead focussed on projecting strong vowel sounds with exaggerated mouth movements.

Ojay’s team saw significant improvements in the snoring of those who consistently sung. More in-depth studies have since confirmed Ojay’s findings, showing improvements in sleepiness, frequency and volume of snoring for a larger group of 93 patients in a recent randomised controlled trial [10].

Ojay continues to advocate singing as a therapy for snoring with her “Singing for Snorers” CDs.


Didgeridoo playing as an alternative treatment for obstructive sleep apnea syndrome – Puhan et al, 2006 [11]

In this small but well-known study, 25 patients with moderate obstructive sleep apnea (AHI 15-30) were randomised to 2 groups. The study group of 14 patients were given didgeridoo lessons for four months and told to practice regularly at home. The remaining 11 were left on a waiting list as a control.

Playing the didgeridoo is hard and requires strong mouth, tongue and throat muscles. A different and fun activity, adherence to the “treatment” was high, patients averaging 5.9 days a week of practice for 25.3 minutes per day.

Compared to the control group, the didgeridoo group showed on average less sleepiness (3 points less on the Epworth Sleepiness Scale), reduced OSA severity (reduced AHI score by 6.2) and disturbed the sleep of partners less.


Conclusion

The studies mentioned are the best examples of using oropharyngeal exercises to combat snoring and sleep apnea, but are non-exhaustive. There have been plenty of other case reports that have produced positive outcomes [1].

The studies in this article used the same time span of three months, and subtly varied the types of exercise and the time spent doing them. Despite this heterogeneity, the results are consistent and can be summarised as follows:

  • Oropharyngeal exercises reduce snoring both objectively and subjectively.
  • Exercises reduce the severity of obstructive sleep apnea, often changing the classification from moderate to mild or even none.
  • Subjective feelings of tiredness significantly reduce after consistently performing these exercises, with some studies objectively measuring greater time spent in deep sleep.
  • Partners report feeling less disturbed and conflicts arising from snoring reduce.

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References

  1. Macario C, et al. Oropharyngeal and tongue exercises (myofunctional therapy) for snoring: a systematic review and meta-analysis. Sleep 2015; 38(5): 669-675. https://www.ncbi.nlm.nih.gov/pubmed/25348130
  2. Guimaraes KC, et al. Effects of Oropharyngeal Exercises on Patients with Moderate Obstructive Sleep Apnea Syndrome. American Journal of Respiratory and Critical Care Medicine 2009; 179(10): 962-966. https://doi.org/10.1164/rccm.200806-981OC
  3. Guimaraes KC. Soft tissue changes of the oropharynx in patients with obstructive sleep apnea. J Bras Fonoaudiol 1999; 1: 69-75.
  4. Ieto V, et al. Effects of Oropharyngeal Exercises on Snoring. Chest 2015; 148(3): 683-691. https://pdfs.semanticscholar.org/36a8/e559e74d123e9f1087538ab1731f00a1ea84.pdf
  5. Verma RK, et al. Oropharyngeal exercises in the treatment of obstructive sleep apnoea: our experience. Sleep & Breathing 2016; 20(4); 1193-1201. https://doi.org/10.1007/s11325-016-1332-1
  6. Nemati S, et al. The effects of oropharyngeal-lingual exercises in patients with primary snoring. European Archives of Oto-Rhino-Laryngology 2015; 272(4): 1027-1031. https://doi.org/10.1007/s00405-014-3382-y
  7. Baz H, et al. The role of oral myofunctional therapy in managing patients with mild to moderate obstructive sleep apnea. PAN Arab Journal of Rhinology 2012; 2(1): 17-22. http://www.academia.edu/12781370/The_role_of_oral_myofunctional_therapy_in_managing_patients_with_mild_to_moderate_obstructive_sleep_apnea
  8. Diaferia G, et al. Effect of speech therapy as adjunct treatment to continuous positive airway pressure on the quality of life of patients with obstructive sleep apnea. Sleep Med 2013; 14: 628–35. http://www.sleepclinic.be/wp-content/uploads/Effect-of-speech-therapy-as-adjunct-treatment-to-continuous-positive-airway-pressure-on-the-quality-of-life-of-patients-with-obstructive-sleep-apnea.pdf
  9. Ojay A and Ernst E. Can Singing Exercises Reduce Snoring? A Pilot Study. Complementary Therapy Medicine 2000; 8: 151-156. https://doi.org/10.1054/ctim.2000.0376
  10. Hilton MP, et al. Singing Exercises Improve Sleepiness and Frequency of Snoring among Snorers – A Randomised Controlled Trial. International Journal of Otolaryngology and Head & Neck Surgery 2013; 2: 97-102. https://www.creativenz.govt.nz/assets/ckeditor/attachments/1086/singing_reduces_snoring_by_o_jay_and_ernst.pdf?1413517377
  11. Puhan MA, et al. Didgeridoo playing as an alternative treatment for obstructive sleep apnea syndrome: randomized controlled trial. British Medical Journal 2006; 332(7536): 266-270. https://www.ncbi.nlm.nih.gov/pubmed/16377643