1
Introduction
Sleep-disordered breathing (SDB) comprises a wide spectrum of sleep-related breathing abnormalities; those related to increased upper airway resistance include snoring, upper airway resistance syndrome (UARS), and obstructive sleep apnea/hypopnea syndrome (OSAHS).
First identified in 1976, Christian Guilleminault diagnosed children with a sleep apnea syndrome similar to that seen in adults by means of polysomnography. He found that excessive daytime sleepiness, a decrease in school performance, abnormal daytime behavior, recurrent enuresis, morning headaches, abnormal weight, and progressive development of hypertension suggested the possibility of a sleep apnea syndrome when any of these symptoms is associated with loud snoring interrupted by pauses during sleep.
Primary snoring (PS) has been considered the most benign form of SDB, and treatment in the past has not usually been prescribed. Current studies suggest that PS may not be as benign as had formerly been considered. A significant proportion of children with PS persist with SDB symptoms even 5 years after the diagnosis.
Children with non-hypoxic, non-apneic PS may exhibit significant neurocognitive and/or neurobehavioral impairments (Bonuck 2012). Consequences may be similar to those associated with UARS or obstructive sleep apnea (OSA). Compared with children who had never snored, children with PS had more hyperactive (39% vs. 20%) and inattentive behavior (33% vs. 11%), as well as poor school performance in mathematics (29% vs. 16%), science (23% vs. 12%), and spelling (33% vs. 20%; all P values <.05). PS was a significant risk factor for hyperactive behavior and inattentive behavior, as well as daytime sleepiness. PS was also an independent risk factor for poor school performance in mathematics, science, and spelling.
Along with daytime impairments, snoring can be associated with sleep problems. An increasing prevalence of sleep problems was found with increasing snoring frequency for sleep-onset delay, night awakenings, and nightmares. Long-term habitual snorers were at significantly increased risk for sleep–wake transition disorders (e.g. rhythmic movements, hypnic jerks, sleep talking, bruxism); odds ratio sleep hyperhidrosis disorders of arousal/nightmares (e.g. sleepwalking, sleep terrors, nightmares, and excessive somnolence [i.e. difficulty waking up, morning tiredness, daytime somnolence; 6.3, 2.2-17.8]). Ex-habitual snorers were at increased risk for sleep–wake transition disorders. Habitual snoring was associated with several sleep problems in our study. Long-term habitual snorers were more likely to have sleep problems than children who had stopped snoring spontaneously.
The American Academy of Pediatrics has recommended that all children who snore be evaluated. The best test to investigate whether snoring is a health risk is the nocturnal polysomnogram (PSG). However, there are many variations in what are considered normal or abnormal PSGs in children. It has also been seen that an Apnea-Hypopnea Index value cannot be the sole determinant in evaluating SDB in children. Children who have chronic snoring and do not respond to the criteria for OSA syndrome can present with an abnormal sleep electroencephalogram, as evidenced by a significant increase in cyclic alternating pattern rates, with a predominance of abnormalities in slow-wave sleep.
The investigation of craniofacial growth patterns is also important, and the impairment of skeletal maxillomandibular growth and development in either or all directions of three-dimensional space is critical when considering a diagnosis of SDB in children. Specifically, if the width, length, and depth of a growing child’s mandible and palatal-facial suture complex are restricted by environmental influences and/or genetic mechanisms, among the negative consequences of such growth inhibitions is often naso-respiratory incompetence. The impairment of nasal breathing leads to noisy breathing, increases in respiratory effort, mouth breathing, and further abnormal skeletal development that can affect upper airway size and shape. This skeletal change occurs long before the puberty-related soft tissue enlargement. Age subdivision is also critical during the prepuberty years, as 60% of the adult craniofacial features will be developed by 4 years of age, and 90% by around 12 years of age.
OSA in children has emerged not only as a highly prevalent condition, but also as a disease that can impose a large array of comorbidities, some of which may have long-term implications extending past adolescence and well into mid/late adulthood. Major deleterious sequelae of pediatric OSA can include neurologic issues, cardiovascular and endocrine disease, and dysfunction of other metabolic systems such as appetite dysregulation and risks associated with excessive body weight (e.g. SDB/OSA, type 2 diabetes, etc.). The underlying pathophysiologic mechanisms of OSA-induced end-organ injury are now being unraveled and clearly involve oxidative and inflammatory pathways. However, the roles of individual susceptibility, such as might be dictated by single-nucleotide polymorphisms, and of environmental and lifestyle conditions, such as diet, physical, and intellectual activity, may account for a substantial component of the variance in phenotype.
2
Evolutionary Considerations
2.1
Cultural Industrialization and Genomic-Environmental Mismatch
The relatively recent appearance of chronic Western diseases, or so-called noncommunicable diseases (NCDs) in humans, such as obesity, type 2 diabetes, cardiovascular disease, etc., is not accurately explained as somehow resulting from recent, and therefore anomalous, macro-genomic change over the past few centuries when prevalence of these health problems has grown to near-epidemic proportions, most notably in many industrialized societies. A more plausible explanation is likely to be found when evaluating the problem from an evolutionary perspective, that is, when critically evaluating why natural selection, the Darwin-proposed force driving either adaptive change or extinction, has apparently left contemporary humans vulnerable to NCDs. An argument can be made that human malocclusion, the term most often used to describe underdevelopment of various craniofacial structural components, specifically of the jaws, facial bones, and associated crowding and misalignment of teeth, is yet another NCD that also has only recently reached near-epidemic proportions worldwide and afflicts people of all ages, but seldom appears in extant aboriginal populations until after exposure to modern industrialized influences. It is now clearly understood that most forms of craniofacial maldevelopment can often be bidirectionally associated with under-development of upper respiratory anatomic structures, or simply stated, genetic and/or environmental factors affecting growth and development of the masticatory apparatus can also affect growth and development of the respiratory apparatus, and vice versa. For example, Harvold showed that under experimental conditions, impairing naso-respiratory competence in monkeys resulted in structural malformations of their mandibles, maxillas, and teeth alignment; in contrast to this, a postmortem analysis of several infants who had apparently died of respiratory complications showed that all were found to have retrognathic mandibles and high and narrow (ogival) hard palates.
For the purpose of using terminology that better represents the intimate connection between craniofacial and respiratory structural anatomy, the term craniofacial-respiratory (CFR) would seem to be more accurate than is craniofacial alone. Accordingly, the term craniofacial anomalies , a commonly used term within the scientific literature when describing SDB/OSA-associated malocclusion traits in syndromic individuals (e.g. retro-positioned mandibles, mid-face deficiency, vertical jaw growth, etc.), can be substituted with CFR maldevelopments as a more encompassing descriptor, in that it better represents SDB-OSA malocclusion phenotypes that commonly occur with high frequency in both syndromic and nonsyndromic individuals.
As previously stated, malocclusion is a condition that had been nearly non-existent throughout the some 200,000+ years of anatomically modern human history but is now, according to Proffit, more highly prevalent than it was even a few hundred years ago. Larsen reports that as humans veered from the hunter-gatherer model toward a transitional shift to more intensified agricultural sustenance strategies, there was also a gradual increase in dental crowding, which seems to become more severe with cultural industrialization. Observations from Gilbert reveal that “jaw anomalies” (i.e. CFR maldevelopments) are relatively new to European populations, as skeletons from the 15th and 16th centuries show almost no malocclusion. Lieberman reports “there is much circumstantial evidence that jaws and faces do not grow to the same size that they used to.”
Given that high prevalence of pediatric SDB/OSA and malocclusion are both relatively recent public health dilemmas that are often comorbid, it seems useful to posit a possible connection between these two maladies. Many children with SDB, often but not always, additionally have one or some combination of the following malocclusion traits: most notably, angle class II skeletal malocclusion with associated retro-positioned mandible, retrognathic maxilla, narrow dental arches/dental crowding, steep mandibular plane angle/hyper-divergent craniofacial growth pattern, anterior open bite, anterior and posterior cross-bites, excessive dental attrition, excessive dental overjet, excessive dental overbite, and ogival (high and narrow-vaulted) hard palate.
As many modern NCDs are now better understood when viewed from an evolutionary perspective, that is, through learning and applying fundamental tools from the basic life sciences of evolutionary biology and anthropology, health care professionals can become adept at a unique approach to solving medical dilemmas in much the same manner as would a forensic anthropologist help solve a crime scene. Evolutionary medicine (EM), also known as Darwinian medicine , is a novel approach to understanding modern NCD pandemics; in fact, Randolph Nesse, considered to be one of the pioneering forces behind the EM educational framework, has often openly discussed the relative absurdity associated with ignorance in this most basic of life sciences.
Evolutionary oral medicine (EOM) is an application of the EM framework whose goals are to understand specific non-communicable oral diseases within an evolutionary context, most notably, the two plaque-mediated dental problems of early periodontal disease (gingivitis) and dental caries (cavities), and also skeletal-dental malocclusion. In much the same manner as exists with the EM model, EOM aims to use this understanding to develop diagnostic, preventive, clinical treatment and research strategies. The etiology of malocclusion is best understood in accordance with Nesse, Williams, and others, who proposed the mismatch hypothesis for explaining modern human disease vulnerability. This hypothesis posits that the current high prevalence of certain NCDs, such as malocclusion in industrialized populations, is due at least in part to exposure to modern feeding regimens mostly consisting of softer processed and cooked foods and other environmental conditions that are vastly dissimilar or mismatched to an anciently derived genome that had been best adapted to prolonged chewing of minimally processed and seldom-cooked firm foods of the Paleolithic/pre-Paleolithic eras. A general lack of masticatory challenge from infancy and early childhood to a masticatory apparatus that had evolved to be constantly challenged over a lifespan is why many anthropologists and many other anthropologically informed dental and medical health professionals speculate that the relatively weak pressures posed by bottle feeding, weaning with soft purees, and later lifetime consumption of highly processed foods seems to offer a sound explanation for why worldwide prevalence of malocclusion, and associated airway problems, have only recently spiked in Western-exposed cultures.
2.2
Pathophysiology of NCDs
It is apparent that most NCD health disparities (i.e. mismatch phenotypes) apparently follow a distinguishable continuum of progression of pathophysiology:
- 1.
They are often preventable ; that is, the disease phenotype will actually never be expressed if a genetically susceptible individual can be identified before becoming symptomatic and somehow remain unexposed to harmful environmental triggers. For example, if the gene sequence by which an individual can be rendered susceptible to the disorder of lactose intolerance is identifiable before showing symptoms, the person can remain free of the intolerance for as long as dietary intake of lactose is completely avoided.
- 2.
These conditions are sometimes reversible if a symptomatic person is identified very early in the disease state; for example, if a potential type 2 diabetic is still in the early stages of pre-diabetic insulin resistance/glucose intolerance, specific lifestyle changes in diet, physical activity, and improved sleep-airway hygiene can actually reverse an impaired glycemic-control phenotype back to a more healthy state.
- 3.
These conditions can be controllable if the disease state has progressed beyond reversibility but can still be managed with appropriate intervention modalities; for example, if a maldeveloped CFR complex in early childhood is allowed to become progressively worsened beyond adolescence when CFR growth has ceased, associated esthetic issues (unattractive smile) and functional problems (impaired naso-respiratory competence) can be addressed respectively with orthodontic tooth alignment or continuous positive airway pressure (CPAP) with or without mandibular advancement devices.
- 4.
When not reversed or adequately controlled with treatment intervention, NCDs can potentially result in increased morbidity and mortality; for example, if an individual suffering from any of the aforementioned lifestyle-modulated NCDs fails to follow a prescribed course of evidence-based therapeutic intervention, their health span and lifespan will become markedly reduced.
2.3
CFR Maldevelopment and SDB/OSA Intervention Strategies
If one accepts the premise that two highly prevalent health care problems, SDB/OSA and malocclusion, can often be accurately categorized as NCDs and thus will follow a pattern of pathophysiology that indicates possible preventability, reversibility, treatability, and disability, it stands to reason that health care professionals from all pertinent disciplines should collaborate in helping at-risk individuals get identified as early in life as is feasible. Specifically, because there is now ample published evidence in the peer-reviewed scientific literature to suggest a bidirectional pathophysiologic relationship between SDB/OSA and identifiable CFR maldevelopments (i.e. malocclusion), it becomes imperative that collaboration between allied medical and dental professionals begin earlier in childhood than is current practice. Specifically, according to a promotional pamphlet from the American Association of Orthodontists (AAO), the AAO recommends that a child’s initial orthodontic screening should be on or before the age of 7 (when approximately two-thirds of CFR growth and development are already completed); however, they also state that most orthodontic treatment does not usually begin until about age 11 (i.e. when the majority of CFR growth and development have already been completed). In light of what is now well understood about how retrusive and constricted CFR phenotypes are co-morbid with pediatric SDB/OSA and are also often first detectable in the primary dentition, and usually persistent and worsen in later childhood and beyond in the absence of appropriately timed and applied evidence-based intervention, it becomes apparent that the AAO should seriously consider revising this message to the public ( Fig. 74.1 ).
