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Yawning: its cycle, its role
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Fetal yawning assessed by 3D and 4D sonography
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Le bâillement : de l'éthologie à la médecine clinique
Le bâillement : phylogenèse, éthologie, nosogénie
 Le bâillement : un comportement universel
La parakinésie brachiale oscitante
Yawning: its cycle, its role
Warum gähnen wir ?
 
Fetal yawning assessed by 3D and 4D sonography
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mystery of yawning 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

mise à jour du
1 octobre 2014
Eur Arch Otorhinolaryngol
2014
Importance of yawning in the evaluation
of excessive daytime sleepiness:
a prospective clinical study
 
Catli T, Acar M, Hanci D, Arikan OK, Cingi C.
Department of Otorhinolaryngology, Bozyaka Teaching and
Research Hospital, Karabag¨lar, Izmir, Turkey

Chat-logomini

 
Abstract
 
As a dark and not fully understood side of human nature, yawning is believed to be a signs of various physiological or pathological behaviors of human. In this study, we aimed to investigate the importance of yawning in the evaluation of sleepiness. One hundred and twenty-nine snorers who were suspected to have obstructive sleep apnea syndrome underwent polysomnography and were asked to fill the Epworth sleepiness scale. The number of yawnings of patients was counted during the day following polysomnography. Patients were stratified into two groups: those have apnea hypopnea index <5 (n = 43, group 1) and those have apnea hypopnea index >30 (n = 86, group 2). Mean duration of sleep phases, oxygen saturations, sleep efficacies, yawning frequencies and Epworth scores of the groups were compared. Correlations of yawning frequency with Epworth scores, duration of sleep phases and mean oxygen saturations were investigated. Sleep efficacies were similar between the groups (p > 0.05). Yawning frequencies in group 1 and group 2 were 43.48 and 75.76 (mean rank), respectively (p < 0.01). Mean N1, N2, N3 phase durations and oxygen saturations were significantly lower in group 2 (p < 0.01). While there was a negative correlation between yawning frequency and duration of the non-REM phases and mean oxygen saturation (r = -0.53 and r = -0.31, respectively, p < 0.05), yawning frequency was positively correlated with Epworth scores (r = 0.46, p < 0.05). In addition to the shortened phases of sleep, increased Epworth score and decreased oxygen saturation, increased yawning frequency may indicate sleep deprivation.
 
Introduction
 
Obstructive sleep apnea (OSA) syndrome is characterized by deprivation of sleep quality due to the repetitive collapse of the pharyngeal airway and numerous arousals to resume ventilation [1]. Although sleep-related events such as apnea, hypopnea, arousal, reduced oxygen saturation and altered sympathetic system activity are the basic aspects of this syndrome, various consequences of these sleep events such as excessive daytime sleepiness (EDS), social problems, increased likelihood of traffic and occupational accidents, increased cardiovascular events and stroke incidence may occur in the short or long term [2&endash;4]. Among these symptoms, signs and complications, EDS seems to be associated with some of the unfavorable results of OSA, such as increased risk of motor vehicle accidents, work-related accidents, cognitive and psychosocial problems.
 
With the increased awareness of clinicians and people about the importance and possible complications of OSA syndrome, numerous studies have been published regarding different aspects of this disease [5, 6]. A variety of objective and subjective test batteries have been developed for the accurate evaluation of OSA-related EDS. The most commonly used objective and subjective tests are multiple sleep latency test (MSLT), maintenance of wakefulness test (MWT), OSLER (Oxford SLEep Resistance) test and Epworth sleepiness scale (ESS). Since objective methods are complex, expensive and time consuming, ESS is the most frequently used simple, inexpensive, self-administered questionnaire that evaluates and rates EDS in sleep disorders [7].
 
Yawning is an easily observable and quantifiable physiological phenomenon, which is believed to be associated with a feeling of comfort [8]. Although this familiar act is a routine part of humans' daily life, it is no more than 40 years that yawning has been a matter of investigation with advances in neuropharmacology. Yawning is a sophisticated ritual that comprises inspiration phase at the beginning, an acme period characterized with the extensive contraction of the mimic muscles together with a momentary interruption of breathing and a final expiration phase, which involves the relaxation of all participating muscles. Various physiological and pathological associations have been proposed with yawning in recent years [9]. While various topics such as ''arousal, brain cooling, social empathy, ear pressure and brain hypoxia'' have been associated with its physiological aspect, numerous pathological conditions such as ''migraine, depression, Parkinson's disease, renal insufficiency, gastro-esophageal reflux'' have also been associated with the occurrence of altered quantity and quality of yawning [10]. Although there is a common belief regarding the association between yawning and sleepiness among people from different cultures, there are few studies which investigate this association in the medical literature. At this point, we aimed to investigate the importance of yawning in the evaluation of EDS.
 
Discussion
 
EDS, which is one of the most frequent and troublesome complaints of OSA syndrome, is associated with various unfavorable consequences of this disease such as increased likelihood of traffic accidents, interpersonal problems and reduced productivity [12]. EDS is also reported to reduce quality of life (QOL) in OSA patients [13]. Although the exact molecular mechanisms and factors underlying EDS are not well understood, investigators have ascribed the presence of EDS to nocturnal hypoxemia or sleep fragmentation or both [14, 15]. In OSA patients, increased circulating levels of tumor necrosis factor-a (TNF-a), which results from hypoxia-induced central nervous system inflammation, might play a role in the emerging of sleepiness [16]. Our findings are in agreement with the knowledge that reduced oxygen saturations during apneic episodes might induce hypoxia-related neuronal inflammation in OSA patients, and thus EDS may occur due to the hypoxia-related neuronal damages. Additionally, our findings suggest that decreased oxygen saturation seems to be related with increased sleepiness and YF in OSA patients. Similar to our findings, Schiller stated in his study that yawning was associated with decreased SaO2 and increased carbon dioxide (CO2) concentrations in the human central nervous system [17].
 
In our study, we showed that yawning frequency is negatively correlated with SaO2 and positively correlated with excessive daytime sleepiness and this correlations are consistent with previous findings. In OSA patients, as hypoxia induced central nervous system alterations, sleep fragmentations may lead to sleepiness [18, 19]. Several reports stated that each arousal and each fragmentation results in increased EDS. Previously, Roure et al., stated that sleep apnea and sleep disruption were not the primary determinants of EDS in all OSA patients [20]; however, since AHI is correlated with the ESS score we may suggest that as a patient has more apnea/hypopnea during sleep, it is possible for the patient to experience much more excessive daytime sleepiness. Moreover, since the sleep efficacies of our groups were similar, it is possible to suggest that EDS might be related to other factors than sleep efficacy, such as ''decreased SaO2, shortened N3 phases of sleep and increased AHI''. Concerning about the duration of sleep phases and its relation with excessive daytime sleepiness, it is not impossible to ascribe EDS to shortened N3 phase of sleep according to our findings. While the duration of REM phase of sleep is similar between the groups in our study, significant shortening of the non-REM phases, ''especially the most restorative N3 phase'', might be associated with increased ESS scores and eventually increased yawning frequencies. Studies that investigated biorhythm of yawning have stated that yawning has certain characteristics, which reflects its complicated nature. For example, yawning peaks in the beginning of the morning immediately after awaking. Another peak occurs in the late afternoon and finally it reaches its maximum level late in the evening, especially close to bedtime [21].
 
Similar to these observations, our findings indicate another physiological aspect of this mysterious bio-act. In other words, yawning seems to have a close interaction with diurnal rhythm of the human nature and also with other biologic necessities as sleeping. A previous study, which investigated the association of yawning with the transition between periods of high level activity and low level activity or arousal, stated that yawning was surely only one means of regulating arousal and activity; it may well be a marker of altered level of arousal, rather than a cause [21]. In the light of our findings and other observations, it is possible to associate yawning with sleep. Studies evaluated human adults, provided evidence that yawning occurs approximately 7&endash;8 times a day [21]. An average yawning frequency of our groups was 4&endash;5 and 10&endash;11 per day for groups 1 and 2, respectively. Discrepancy of these average scores might be related to various ''not well-known'' characteristics of the act of yawning. It is obvious that we need more studies regarding the dark sides of yawning in human. In the light of our results, we may conclude that similar to the shortened N3 phase of sleep, increased Epworth scores and decreased oxygen saturations, increased frequency of yawning may indicate sleep deprivation as well. Our findings revealed that daily frequency of yawning seems related to the degree of EDS of a patient. Physicians who involved with obstructive sleep apnea may adapt ''yawning'' to their clinical practice in order to predict the sleepiness of their patient.