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BREATHING AND THE INFLUENCE ON CHILDHOOD DEVELOPMENT:

Dr. Yosh Jefferson in a paper entitled Mouth breathing: adverse effects on facial growth, health, academics, and behavior states the following: “The vast majority of health care professionals are unaware of the negative impact of upper airway obstruction (mouth breathing) on normal facial growth and physiologic health. Children whose mouth breathing is untreated may develop long, narrow faces, narrow mouths, high palatal vaults, dental malocclusion, gummy smiles, and many other unattractive facial features”.

In this paper he also states: “These children do not sleep well at night due to obstructed airways; this lack of sleep can adversely affect their growth and academic performance. Many of these children are misdiagnosed with attention deficit disorder (ADD) and hyperactivity”.

“It is important for the entire health care community (including general and pediatric dentists) to screen and diagnose for mouth breathing in adults and in children as young as 5 years of age. If mouth breathing is treated early, its negative effect on facial and dental development and the medical and social problems associated with it can be reduced or averted”.

Jefferson Y. Mouth breathing: adverse effects on facial growth, health, academics, and behavior. Gen Dent. 2010 Jan-Feb;58(1):18-25; quiz 26-7, 79-80.

For information about upcoming Buteyko breathing courses for Children and their parents visit: Courses

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Mouth Breathing and its Effect on Childhood Development

  • Mouth breathing is a common habit, present in more than 50 percent of children. It is caused by airway obstruction or small airway size. Common risk factors include swollen adenoids and tonsils or a blocked, stuffy nose.
  • Breathing through an open mouth is extremely detrimental to the development of the face, teeth and upper airways. Left untreated in childhood, the habit results in abnormal facial features and smaller airways in adulthood. This perpetuates poor breathing habits and leads to a lifetime of health issues.
  • When a child mouth-breathes, the brain receives insufficient oxygen. Long term, this has been proven to have a direct impact on cognitive ability, learning and behavior.
  • Mouth breathing at night can result in sleep-disordered breathing with problems such as snoring and sleep apnea. No child should ever snore.
  • Sleep-disordered breathing has been linked to cases of cot death.

The Buteyko Technique is a gentle breathing re-education program. It is suitable for everyone. Because it is so important to develop good breathing habits at an early age, the exercises for children are, and always will be, completely FREE. Learn more by watching our free videos.

The early research

In 1909, an article was published in a journal called The Dental Cosmos in which the writer described how mouth breathing affects the development of the face and skull. Children who mouth-breathe, the author explained, are often misinterpreted as being inattentive in class due to their ‘glazed’ expressions. The fact is, there is significant scientific evidence that mouth breathing can lead to poorly developed airways, contributing to a lifelong habit of poor breathing patterns[1]. There is also proof that mouth breathing causes learning difficulties. Human beings are not meant to breathe through their mouths, and children who mouth-breathe will struggle to reach their full potential.

How common is mouth breathing?

Even though it has many functions, from improving oxygen uptake in the blood to filtering and humidifying incoming air, the nose is often underused for the essential task of breathing. Babies are born breathing in and out through their noses, their little tummies moving up and down as they take each breath, but as early as a few months into life, many children switch to habitual mouth breathing. Mouth breathing is considered to be a pathological condition, yet it is present in more than 50 percent of children[2] with a higher incidence in boys (around 60 percent) than girls (about 40 percent)[2].

What causes mouth breathing?

Mouth breathing in children is always caused by some sort of obstruction in the airways or by an airway that is narrow for some reason. One 2018 review found that children with nasal obstruction are 5.55 times more likely to mouth-breathe[3]. Obstruction is often the result of swollen adenoids and/or tonsils. When these soft tissues in the back of the throat are enlarged, the airway becomes much narrower. This is not just an uncomfortable childhood malady. Untreated swollen adenoids can lead to irreversible abnormalities in facial growth. Other things that contribute to mouth breathing include lower airway issues including asthma, thumb sucking, excessive use of pacifiers, a high narrow palate (children with a narrow palate are 2.99 times more likely to mouth-breathe[3]), a small nose[4], tongue-tie (tissue holding the tongue down to the floor of the mouth), lip-tie, deviated nasal septum, bottle-feeding and even environment (an excessively warm or poorly ventilated home).

Conventional pacifiers have been linked to abnormal dental growth[5], and one study found that for each year of pacifier use, the probability of mouth breathing increases by 25 percent[3]. The man-made teats intrinsic to bottle-feeding can produce similar problems. Breastfeeding not only provides your baby with proper nutrition, it also helps the face and jaw muscles develop in a way that bottle-feeding just can’t replicate.

Tongue and lip ties can cause the baby difficulty suckling and prevent correct positioning of the tongue. If the mouth is hanging open, the tongue will not rest naturally against the roof of the mouth. Try it for yourself. Place three-quarters of your tongue on the roof of your mouth, then open your mouth and try to breathe. It’s not easy. Along with nasal breathing, the position of the tongue is important as it moulds the top jaw into a wide U shape, ensuring a healthy, attractively proportioned face with enough room in both jaws for all of the adult teeth. I once heard a speaker at a sleep conference describe how midwives in sixteenth century France had an extra long finger nail to release tongue ties of babies soon after birth. Bizarre as it may sound, this may have been the difference between life and death for those children.

Another common cause of mouth breathing is a condition called allergic rhinitis, an inflammatory disorder that affects about 40 percent of children[6]. Rhinitis creates symptoms including nasal discharge, sneezing, blocked nose, palatal itching, mood swings and tiredness, most of which are also common to children who mouth-breathe, and can be relieved by learning to breath through the nose.


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Mouth breathing affects learning ability, behavior and psychological wellbeing

In 1998, the first major study into the possible link between obstructive sleep apnea and its negative impact on cognitive ability was published. The paper looked at 297 first-grade students who were in the bottom ten percent of their class academically. The children who were struggling in school were found to have a much higher prevalence of OSA than their classmates. When they received treatment, their results improved dramatically[7].

Research has also demonstrated that if a child aged 8 is left with untreated snoring, there is an 80 percent chance that he or she will develop a 20 percent lifelong reduction in mental capacity[8]. Mouth breathing, sleep apnea and snoring in early childhood increase the risk of neurocognitive and behavioral problems by the age of four [9], and children with sleep-disordered breathing are 40 percent more likely to develop special educational needs (SEN)[10]. A 2015 study looking at reading, arithmetic and working memory found impairments in all three categories in children who mouth-breathed [11].

When your child’s nose is blocked, his or her sleep will be affected. Daytime tiredness caused by poor sleep means poor concentration in school, and over time, this difficulty focusing can lead not only to problems with cognition and working memory, but to a diagnosis of ADHD. There is a direct relationship between breathing and these neuropsychiatric disorders: Children with ADHD tend to have a higher incidence of allergic rhinitis and nasal congestion[12], and 40 percent of children who suffer from sleep disorders including sleep apnea and snoring develop ADHD, ADD or a learning disability[13]. When I speak to any parent who has a child labeled with ADD or ADHD, my advice is to check their sleep habits.

A 2017 paper by pediatric behavioral and sleep experts described the case of a five-year old girl called Carly who demonstrated behaviors cohesive with ADHD at home and school. Carly’s IQ scores and verbal fluency were normal, but working memory and processing speed were below average. The little girl’s home life involved multiple caregivers who had inconsistent approaches to discipline – her mother worked nights and her parents were recently separated. She showed evidence of mouth breathing and snoring during sleep, but no daytime sleepiness. A physical examination showed a high arched palate and enlarged tonsils, and a sleep study indicated OSA. Carly underwent an operation to remove her adenoids and tonsils, after which her ADHD symptoms improved significantly. However, one year after surgery her behavioral problems re-emerged [14] – this is consistent with evidence that without restoration of nasal breathing, sleep disordered breathing is likely to recur within three years of surgery[15].


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Habitual mouth breathing in childhood causes abnormal development of the face and teeth

A close relationship has been proven between mouth breathing during childhood and abnormal facial growth. If the mouth is hanging open, gravity pulls the face downwards, resulting in narrow jaws and overcrowded teeth that become set back in the face, reducing the width of the upper airway. This narrow airway causes lifelong sleep-disordered breathing including sleep apnea, the poor academic performance and behavioral issues we’ve already covered, and a less attractive face.

The link between mouth breathing and straight teeth was first examined in the 1970s by a Norwegian orthodontist called Egil Harvold who spotted that many of his patients who had dental problems were also mouth breathers. Harvold set up a landmark study[16] to examine how mouth breathing altered the craniofacial development of baby monkeys. His experiment compared a group of monkeys whose nostrils were blocked with silicone plugs, forcing them to mouth breathe by default, with a control group who had no nasal obstruction. As they grew, the faces of the mouth-breathing monkeys began to look very different from the control monkeys. Their faces became long, their teeth, crooked, and their facial and neck muscles adapted to form an oral airway. Even after the nasal plugs were removed, the animals continued to mouth breath for up to a year, and their distorted facial features were permanently retained. While this was the first, and for a long time the only study of its kind, a 1997 experiment using monkeys supported the theory that nasal congestion in childhood, both before and during puberty, may cause lasting deformities[17]. And 2011 research into the effects of forced oral breathing on baby rats showed that even short term nasal congestion caused an increase in stress hormones of over 1,000 percent and created long-term alterations in the development of the respiratory muscles[18].

Relationships have also been found between mouth breathing and poor dental health, tooth decay and halitosis,[2] though research in this area is still scarce. A 2019 study in the European Journal of Pediatric Dentistry advised that mouth breathing, among other oral habits, can be instrumental in the development or worsening of malocclusion [19] – misalignment or incorrect relation between the teeth of the upper and lower jaws when they move together as the jaws close. Researchers found that 46 percent of preschoolers showed risk factors and early indications of malocclusion and needed monitoring for speech therapy, allergies, exercises to help develop the chewing and swallowing muscles or ear nose and throat (ENT) treatment [20]. The study concluded that dentists should aim promote correct growth of the face by reducing risk factors such as mouth breathing, and that early diagnosis and treatment relied on close collaboration between pediatricians, ENT specialists, allergists, orthodontists and speech therapists.


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My child has swollen adenoids and tonsils. What should I do?

One of the biggest causes of mouth breathing in children is inflammation in the soft tissues at the back of the throat – the adenoids and tonsils. These tissues can also become inflamed because of mouth breathing. Breathing cold, unfiltered air through an open mouth can make the throat very dry and lead to irritation and swelling. This perpetuates mouth breathing and plays a significant role in sleep-disordered breathing.

When a child has problems with the adenoids and tonsils, it may be that he or she also has a small airway. For example, a child who suffers with adenoid hypertrophy is likely to have a high narrow palate, narrow jaws, and a narrow upper airway. These craniofacial features may have developed as the result of habitual mouth breathing, or they may be genetic. Either way, the airway is central both to the problem and the solution. It is just as important to identify risk factors for a small, narrow airway as it is to diagnose swollen adenoids and tonsils. It may be easier to understand this when you realize that some children with enlarged tonsils don’t suffer from sleep-disordered breathing. Their airway is a good size, so they can still breathe freely through the nose. Airway size plays a fundamental role in healthy breathing.

It is possible to have the adenoids and tonsils removed. In fact, this is one of the most common forms of treatment for OSA in non-obese children. It is also acknowledged that the size of the airway is a significant factor in the success of this operation. However, in many cases, the tonsils and adenoids are removed, and nothing is done to develop the airway or to restore nasal breathing. Hence, even after the operation, many children are left with sleep-disordered breathing. One 2010 study of 578 children found that sleep apnea was only completely resolved by adenotonsillectomy in 27 percent of cases[21]. Another 2015 review reports that sleep-disordered breathing is likely to recur within three years of surgery if the child is not taught to breathe through the nose[22].

Unfortunately, there is rarely any information or advice given to parents post-operatively about the importance of nasal breathing. In order to get the maximum long-term benefit from the operation, the child’s breathing habits must be corrected. According to pediatric sleep expert, the late Dr. Christian Guilleminault, co-author of the 2015 study[22] and author of many papers on sleep-disordered breathing in children: “Treatment of pediatric obstructive sleep apnea and sleep-disordered breathing means restoration of continuous nasal breathing during wakefulness and sleep; if nasal breathing is not restored, despite short-term improvements after adenotonsillectomy, continued use of the oral breathing route may be associated with abnormal impacts on airway growth and possibly blunted neuromuscular responsiveness of airway tissues. Elimination of oral breathing, i.e., restoration of nasal breathing during wake and sleep, may be the only valid end point when treating OSA.”[23]

Going back to the 2010 study in which 73 percent of children still had sleep apnea after their adenoids and tonsils were removed, researchers concluded that the operation is not consistently effective in curing OSA in children[21]. Factors that leave children with sleep-disordered breathing post-operatively are undefined, and especially given rising rates of obesity in children, the effectiveness of adenotonsillectomy in eradicating sleep apnea “needs to be viewed with great skepticism”.[21]

Despite these assertions, the gold standard of care in sleep medicine still normally involves the removal of the adenoids and tonsils. However, even once these tissues have been removed, children with narrow upper airway will have difficulty breathing through the nose. While the 2010 study did report reductions in numbers of apneas and hypopneas that were felt to be significant, symptoms persisted, notably in many of the children who were obese and older than seven years[21].

On the positive side, decongestant medications such as intranasal steroids have been found to be helpful in mild OSA[24]. This indicates that nasal obstruction contributes to the problem, meaning that simple nose-unblocking exercises can be helpful in treating sleep-disordered breathing. Maxillary expansion (widening of the upper jaw) is also known to resolve sleep-disordered breathing in children, and this may be a particularly pertinent option for children with small upper airways.

So how do you go about exploring the development of your child’s airways to make room for breathing? Parents should consult with a dentist skilled in functional orthodontics. It is important that the dentist specializes in functional orthodontics as not all dentists are qualified to develop the airway. In fact, many traditional dental procedures can actually compromise airway size, and knowledge about the effects of mouth breathing on craniofacial development is not yet integrated into dental training.

Early intervention is important where possible. The window of opportunity to restore nasal breathing and direct the development of the child’s face is relatively small. The face is already 90 percent developed by the time the child is eleven or twelve years old. One study found that the face grows most in the first five years, with changes to facial bones happening most rapidly in the first six months of life[25]. By the time a child is four-years-old, the face is 60% developed[26]. This does not mean that there are no treatment options for pre-teens, teenagers and adults. According to a 2018 article in the American Journal of Otolaryngology and Head and Neck Surgery, it’s never too late to address a breathing pattern disorder[26]. However, the longer you leave it, the more difficult the problem is to correct, and the more challenging the process will be for the patient.

I recommend that parents ask their functional orthodontist about forward development of the airways and maxillary expansion (widening of the upper jaw) before considering an adenotonsillectomy for their child. Try this for three months, along with nasal breathing exercises (children can also practice the Steps exercise) and the problem might just resolve itself, gently restoring nasal breathing and reducing inflammation of the adenoids and tonsils.


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Mouth breathing causes potentially fatal sleep disturbances in children

Snoring is a common sign of sleep-disordered breathing, and mouth breathing is more common among children who snore[27]. Fortunately, sleep experts are becoming increasingly concerned about the impact of open mouth breathing during sleep. Dr. Christian Guilleminault, for example, was a leading figure in the field of sleep medicine. He discovered and named the condition obstructive sleep apnea (OSA), and was the first to spot a connection between breath holding during sleep and heightened blood pressure. Dr. Guilleminault firmly believed that the restoration of nasal breathing during sleep may be “the only valid ‘complete’ correction of paediatric sleep disordered breathing.”[28]

Sleep-disordered breathing in children has also been linked with Sudden Infant Death (SID) syndrome. A paper published in 2012 found correlations between airway obstruction and cot deaths in seven babies[29]. All seven had a history of chronically abnormal sleep, although none of them had a diagnosis of sleep disordered breathing, and most of them had presented with mild respiratory infections in the days before they died. All of the babies had swollen adenoids and tonsils and features consistent with a narrow upper airway. All seven died of oxygen deprivation in their sleep.

The research explains that there are certain risk factors for a narrow upper airway that can be identified early in life. Some are even hereditary, meaning it should be easy to spot at-risk children from family records. Sleep-disordered breathing is normally related to a small upper airway – the extra resistance caused by swollen tonsils, for example, will cause the child to switch to mouth breathing.

How dentists can help

Dr. Kevin Boyd is a pediatric dentist from Chicago. He specializes in anthropology, which means he has a unique understanding of how human teeth and jaws have evolved. Dr. Boyd works with children as young as six months old. He believes that many of the craniofacial features that cause a narrow airway, sleep apnea and sleep disordered breathing can be corrected during early childhood[30], and that dentists should always be aware of the bigger picture when planning procedures such as tooth extraction and retraction of the jaw that can potentially compromise the airway. This belief is also central to the work of Dr. William Hang, a California-based orthodontist who specializes in airway-centric dentistry[31]. Dr. Hang claims that retraction of the lower jaw and extraction of the premolar teeth almost always negatively affects the size of the upper airway.

Research has clarified that OSA is not caused by obesity. It is the result of a long face, swollen adenoids or tonsils, a narrow palate and misaligned teeth – all of which are symptoms of habitual mouth breathing. Of the various health professionals who care for your child, your dentist may be best placed to spot these risk factors, simply because he or she looks into your child’s mouth [32].


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More impacts of mouth breathing on posture and voice

Diagnostic criteria for adenoid facies, which is the clinical term for the abnormal growth of the face and skull due to swollen adenoids, include speech anomalies and difficulty swallowing[33]. Mouth breathing not only causes craniofacial deformities, it creates changes throughout the whole body. Studies have shown that children who mouth-breathe tend to develop a forward head posture that permanently alters the bearing of the head and lumbar column[3]. Long-term, these compensatory changes increase the chance of habitual mouth-breathing[3].

Scientists have also made the connection between mouth breathing and speech. One 2011 study looked at the effect of chronic nasal obstruction on speech and found that 76.6 percent of participants with blocked noses also suffered some form of dysphonia – difficulty speaking due to a physical disorder of the mouth, throat, tongue or vocal cords, and 68.3 percent demonstrated vocal abuse – defined as any behavior that strains the vocal cords[34]. Another paper from 2013 found that: “Mouth breathing can affect speech development, socialization, and school performance. Early detection of mouth breathing is essential to prevent and minimize its negative effects on the overall development of individuals.” [35] Children who mouth breathe develop alterations in posture, tone, and mobility of lips, tongue and cheeks, causing less efficiency in functions such as chewing, swallowing and speech, flaccid jaw muscles, head posture, and speech disorders. These speech disorders include lisps and inability to pronounce certain sounds. The paper explains that children who are mouth-breathers can also have immature auditory processing.

A third study from 2014 looked at speech difficulties in children with enlarged adenoids. This was the first research of its kind, and limited by the small number of participants, but a connection was found between overly enlarged adenoids and articulation errors during speech[36].

Is your child mouth breathing?

The best advice that I can give parents is to monitor their child’s breathing pattern. Try to observe the breathing when your child is concentrating, while doing homework, sleeping or watching TV. Check how long your child maintains an open mouth posture – if the mouth is open at least 40 percent of the time you must take action. If your child has nasal obstruction, I suggest that you teach them the nose unblocking exercise.

  • Is your child breathing through an open mouth?
  • Are they twisting and turning during the night, waking up with the bedclothes tangled in the morning?
  • Do they snore or hold their breath during sleep?
  • Is their breathing audible during sleep?
  • Is sleep disrupted?
  • Do they have nightmares, wake up needing to use the bathroom or wet the bed during the night?
  • Are they tired when they wake up in the morning?
  • Do they complain about having a dry mouth and a blocked stuffy nose when they wake up?

Answering yes to any of these questions may suggest that your child is suffering the detrimental effects of sleep disordered breathing, including obstructive sleep apnea.

Creating Miracle Children – a personal story

In 2010 the birth of my daughter Lauren brought tremendous joy to my wife Sinead and me. Minutes after birth, she was drawn to the breast to feed. Breastfeeding continued for a number of months until we realized that she wasn’t thriving as expected. We introduced the bottle to bridge the gap, but this soon became her primary mode of feeding. Little babies are clever and favor the bottle over the breast, as it requires a lot less work to feed. Once the bottle is introduced, there is little chance of going back!

Lauren thrived. But when she was three years old, I noticed small changes to her breathing pattern. She was reverting more and more to mouth breathing. Her sleep was a little noisier, and when she had a cold I noticed her holding her breath during sleep. My daughter was becoming a mouth breather and showing signs of obstructive sleep apnea – the very same breathing disorders that I experienced throughout my teenage years and which now are my field of work.

Over the next couple of years, I encouraged Lauren to nose-breathe, teaching her a simple exercise to decongest the nose. When she was four years old, I drove from Galway to Cork to see Dr. Tony O’Connor who specializes in functional orthodontics. Tony explained that Lauren was tongue tied, had a narrow upper palate, was missing two adult teeth and that her top jaw was dropping a little downwards. It was time for me to do something about it. Sinead and I booked Lauren for an adenotonsillectomy. I also asked if the ENT surgeon would release Lauren’s tongue and lip tie. Despite the unpleasantness of having my daughter go through this operation, I felt it was absolutely necessary. Within days of the procedure, she bounced back and was able to breathe silently and regularly through her nose during sleep.

My only regret is that I didn’t get Lauren’s tongue-tie released earlier. Tongue-tie makes breastfeeding very difficult for both baby and mother. To express milk from the breast, the tongue needs to move freely up and down. If the tongue is tied to the floor of the mouth by a short frenulum, the baby doesn’t get enough milk and the mother often gets very sore.

The negative effects of chronic mouth breathing are recognized within the medical and dental professions, yet very few parents are aware of them. Animals and human infants are natural nasal-breathers. Although dogs are commonly seen panting with their mouths open, they only do this to regulate body temperature. Few healthy animals mouth-breathe – the only exceptions are diving birds such as the penguin, gannet and pelican. Bearing in mind that the entire animal kingdom uses the nose for breathing, how is it that humans have developed such detrimental breathing habits?

As for Lauren, I am very grateful that I was able to recognize her mouth breathing early on so that I could assist her to develop normal breathing patterns. As a result of this, she no longer shows signs of sleep-disordered breathing. As a child, I was never once encouraged to breathe through my nose, despite years of visiting doctors for asthma medication. In 1997, I read an article in The Irish Independent about the work of Russian doctor Konstantin Buteyko who advocated the importance of breathing through the nose and bringing breathing volume towards normal. This simple advice is a small miracle. It completely changed my life, and it can change the life of your child.

References:

1. DeLong, G.F. Smith, John. “Habitual Mouth-Breathing and Consequent Malocclusion of the teeth.” The Dental cosmos; a monthly record of dental science: Volume 51, Issue 2, February, 1909, 200-204

2. Alqutami, J., W. Elger, N. Grafe, A. Hiemisch, W. Kiess, and C. Hirsch. “Dental health, halitosis and mouth breathing in 10-to-15 year old children: A potential connection.” European journal of paediatric dentistry 20, no. 4 (2019): 274.

3. Milanesi, Jovana de Moura, Luana Cristina Berwig, Mariana Marquezan, Luiz Henrique Schuch, Anaelena Bragança de Moraes, Ana Maria Toniolo da Silva, and Eliane Castilhos Rodrigues Corrêa. “Variables associated with mouth breathing diagnosis in children based on a multidisciplinary assessment.” In CoDAS, vol. 30, no. 4. 2018.

4. Warren, Donald W., W. Michael Hairfield, Debra Seaton, Kathleen E. Morr, and Lynn R. Smith. “The relationship between nasal airway size and nasal-oral breathing.” American Journal of Orthodontics and Dentofacial Orthopedics 93, no. 4 (1988): 289-293.

5. Lima, Andrea Arraes dos Santos Jacintho, Cláudia Maria Coelho Alves, Cecília Cláudia Costa Ribeiro, Alex Luiz Pozzobon Pereira, Antônio Augusto Moura da Silva, Luciana Freitas Gomes E. Silva, and Erika Barbara Abreu Fonseca Thomaz. “Effects of conventional and orthodontic pacifiers on the dental occlusion of children aged 24–36 months old.” International journal of paediatric dentistry 27, no. 2 (2017): 108-119.

6. Tonelli, Leonardo H., Morgan Katz, Colleen E. Kovacsics, Todd D. Gould, Belzora Joppy, Akina Hoshino, Gloria Hoffman, Hirsh Komarow, and Teodor T. Postolache. “Allergic rhinitis induces anxiety-like behavior and altered social interaction in rodents.” Brain, behavior, and immunity 23, no. 6 (2009): 784-793.

7. Gozal, David. “Sleep-disordered breathing and school performance in children.” Pediatrics 102, no. 3 (1998): 616-620.

8. Catalano, Peter. “Understanding nasal breathing the key to evaluating and treating sleep disordered breathing in adults and children.” Current Trends in Otolaryngology and Rhinology (ISSN: 2689-7385) (2018).

9. Bonuck, Karen, Katherine Freeman, Ronald D. Chervin, and Linzhi Xu. “Sleep-disordered breathing in a population-based cohort: behavioral outcomes at 4 and 7 years.” Pediatrics 129, no. 4 (2012): e857-e865.

10. Boyd, Andy, Jean Golding, John Macleod, Debbie A. Lawlor, Abigail Fraser, John Henderson, Lynn Molloy, Andy Ness, Susan Ring, and George Davey Smith. “Cohort profile: the ‘children of the 90s’—the index offspring of the Avon Longitudinal Study of Parents and Children.” International journal of epidemiology 42, no. 1 (2013): 111-127.

11. Kuroishi, Rita Cristina Sadako, Ricardo Basso Garcia, Fabiana Cardoso Pereira Valera, Wilma Terezinha Anselmo-Lima, and Marisa Tomoe Hebihara Fukuda. “Deficits in working memory, reading comprehension and arithmetic skills in children with mouth breathing syndrome: analytical cross-sectional study.” Sao Paulo Medical Journal 133, no. 2 (2015): 78-83.

12. Brawley, Ashley, Bernard Silverman, Shannon Kearney, Denise Guanzon, Mark Owens, Harvey Bennett, and Arlene Schneider. “Allergic rhinitis in children with attention-deficit/hyperactivity disorder.” Annals of Allergy, Asthma & Immunology 92, no. 6 (2004): 663-667.

13. Goyal, Abhishek, Abhijit P. Pakhare, Girish C. Bhatt, Bharat Choudhary, and Rajesh Patil. “Association of pediatric obstructive sleep apnea with poor academic performance: A school-based study from India.” Lung India: Official Organ of Indian Chest Society 35, no. 2 (2018): 132.

14. Won, Dana C., Christian Guilleminault, Peter J. Koltai, Stacey D. Quo, Martin T. Stein, and Irene M. Loe. “It Is Just Attention-Deficit Hyperactivity Disorder… or Is It?.” Journal of developmental and behavioral pediatrics: JDBP 38, no. 2 (2017): 169.

15. Christian Guilleminault, D. M. “Mouth breathing,“nasal dis-use” and pediatric sleep-disordered-breathing Seo-Young Lee*, Christian Guilleminault, Hsiao-Yean Chiu,**, Shannon S. Sullivan Stanford University Sleep Medicine Division, Stanford Outpatient Medical Center, Redwood City CA.”

16. Harvold, Egil P., Britta S. Tomer, Karin Vargervik, and George Chierici. “Primate experiments on oral respiration.” American Journal of Orthodontics and Dentofacial Orthopedics 79, no. 4 (1981): 359-372.

17. Yamada, Tetsuro, Kazuo Tanne, Keisuke Miyamoto, and Kazuo Yamauchi. “Influences of nasal respiratory obstruction on craniofacial growth in young Macaca fuscata monkeys.” American journal of orthodontics and dentofacial orthopedics 111, no. 1 (1997): 38-43.

18. Padzys, Guy Stéphane, Jean-Marc Martrette, Christiane Tankosic, Simon Nigel Thornton, and Marie Trabalon. “Effects of short term forced oral breathing: physiological changes and structural adaptation of diaphragm and orofacial muscles in rats.” Archives of oral biology 56, no. 12 (2011): 1646-1654

19. Wikipedia contributors, “Malocclusion,” Wikipedia, The Free Encyclopedia, https://en.wikipedia.org/w/index.php?title=Malocclusion&oldid=938275878 (accessed January 30, 2020).

20. Paolantonio, E. G., N. Ludovici, S. Saccomanno, G. Torre La, and C. Grippaudo. “Association between oral habits, mouth breathing and malocclusion in Italian preschoolers.” European journal of paediatric dentistry 20, no. 3 (2019): 204-208.

21. Bhattacharjee, Rakesh, Leila Kheirandish-Gozal, Karen Spruyt, Ron B. Mitchell, Jungrak Promchiarak, Narong Simakajornboon, Athanasios G. Kaditis et al. “Adenotonsillectomy outcomes in treatment of obstructive sleep apnea in children: a multicenter retrospective study.” American journal of respiratory and critical care medicine 182, no. 5 (2010): 676-683.

22. Lee, Seo-Young, Christian Guilleminault, Hsiao-Yean Chiu, and Shannon S. Sullivan. “Mouth breathing,“nasal disuse,” and pediatric sleep-disordered breathing.” Sleep and Breathing 19, no. 4 (2015): 1257-1264.

23. Guilleminault, C., and S. S. Sullivan. “Towards restoration of continuous nasal breathing as the ultimate treatment goal in pediatric obstructive sleep apnea.” Enliven: Pediatr Neonatol Biol 1, no. 1 (2014): 001.

24. Tan, Hui-Leng, David Gozal, and Leila Kheirandish-Gozal. “Obstructive sleep apnea in children: a critical update.” Nature and science of sleep 5 (2013): 109.

25. Liu, Yi-Ping, Rolf G. Behrents, and Peter H. Buschang. “Mandibular growth, remodeling, and maturation during infancy and early childhood.” The Angle Orthodontist 80, no. 1 (2010): 97-105.

26. Catalano, Peter J, and John Walker. “ADD & ADHD in Children: The Answer is Right in Their Nose.” American Journal of Otolaryngology and Head and Neck Surgery no. 1, Issue 5, Article 1025 (2018): 1-2.

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