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Le bâillement, du réflexe à la pathologie
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
Le bâillement foetal
Le bâillement, du réflexe à la pathologie
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
Le bâillement foetal

mise à jour du
3 octobre 2010
12 septembre 2010
Sleep Breath
Excessive yawning and thermoregulation: two case histories of chronic, debilitating bouts of yawning
Gordon G. Gallup Jr. Andrew C. Gallup
Department of Psychology, University at Albany, USA
Department of Biological Sciences, Binghamton University, NY


Andrew C. Gallup. Yawning and the thermoregulatory hypothesis
Background This report details the case histories of two women who suffer from chronic and debilitating episodes of excessive yawning in the absence of sleep problems.
Methods Each woman independently provided information and answered questions about their excessive yawning symptoms and medical histories.
Results Both women show signs of thermoregulatory dysfunction, and each reports symptom relief and/or the postponement of yawning attacks through means of behavioral cooling. One woman recorded her body temperature before and after bouts of yawning, revealing a significant drop in temperature following each episode (p<O.O5).
Conclusions The trigger for yawning in these patients appears to be related to increases in body/brain temperature. These cases are consistent with growing evidence showing that recurrent episodes of excessive yawning are not necessarily associated with a sleep disorder, but rather may be indicative of thermoregulatory dysfunction.
For most people, yawning occurs in a consistent fashion throughout life, with frequent instances of yawning occurring during the first hour after waking and the last hour before sleeping [1-3]. Excessive yawning is generally viewed as a symptom reflecting a sleep disorder and/or sleep deprivation. Contrary to popular belief, however, the frequency of yawning is not correlated with sleep duration [3].
There is little consensus as to the functional significance of yawning [4]. One commonly held view is that yawning functions to equilibrate oxygen levels in the blood; however, yawning is unaffected in subjects that breathe increased levels of oxygen or carbon dioxide [5]. Recent evidence suggests that yawning is involved in thermoregulation and may act as a brain cooling mechanism [6, 7]. According to this model, increases in facial blood flow resulting from a yawn operate like a radiator removing hyperthermic blood from the face and head, while introducing cooler blood from the lungs and extremities. The respiratory and arterial actions triggered by a yawn are similar to those that promote cerebral cooling [6, 7]. In addition, excessive yawning has been linked to certain medical conditions involving abnormal thermoregulation (e.g., multiple sclerosis and epilepsy), and research reveals that yawning occurs before, after, and during instances of heat stress or hyperthermia [7].
The brain cooling hypothesis is consistent with the fact - that the incidence of yawning follows a circadian pattern [1-3]. Thermoregulation and sleep are interconnected, and the temperature changes before and after sleep act in a positive feedback loop as core body temperature and sleep vary inversely [8]. For instance, body temperature begins to peak in the evening and the onset of sleep initiates a decline in the core body temperature curve, and likewise, the tendency to wake-up occurs in tandem with a rise in core body temperature in the morning. Therefore, the highest frequency of yawning occurs when body temperature is highest in the evening, and when it rises in the morning.
Here, we report two women who suffer from recurring episodes of excessive and debilitating yawning that include symptoms of thermoregulatory dysfunction. Neither woman reports sleep problems, nor have they been accurately diagnosed.
Materials and methods
Two women independently contacted us about their experience with chronic bouts of debilitating yawning. One patient is a 39-year-old woman from South Africa and the other is a 61-year-old woman from the USA. Both are Caucasian, college educated, married, reasonably healthy, and have children. Each patient was asked to describe their symptoms and to provide their medical histories regarding their condition. The local university institutional review board approved this research and both individuals gave consent to participate in this study.
Case 1
The first person to contact us was a 39-year-old woman from South Africa. She is 1.72 m tall and weighs 62 kg. Her previous medical history included chicken pox and whooping cough as a child and malaria once as an adult. She was diagnosed with polycystic ovulatory syndrome and insulin resistance while flying to conceive, and was treated with metformin, which resolved the problem. Her blood pressure is normal and her cholesterol is slightly high, but she does not take medication for it.
Her pathological yawning attacks began 8 years ago and due to the extreme debilitating nature of these episodes (i.e., inability to walk, feeling ill, or extreme discomfort), she immediately sought medical assistance. She has seen 13 doctors about this problem, including two general practitioners; four neurologists; a dentist; an endocrinologist; an ear, nose, and throat specialist; two physicians; a maxillofacial surgeon from a headache clinic; and a neuropsychologist. She has received diagnoses of narcolepsy, pathological yawning, seizure, migraine activity, excessive daytime sleepiness, and insulin resistance. Blood tests have shown nothing other than high fasting insulin levels, confirming insulin resistance. Magnetic resonance imaging (MRI) has revealed no problems, MSLT and polysomnograms are negative for narcolepsy and hypersomnolence, and EEG is normal. Diagnoses which have been ruled out are narcolepsy and excessive daytime sleepiness. She has been prescribed a number of drugs including reactivan, metformin, sodium valproate, modafinil, folie acid supplementation, and 5-hydroxytryptophan. All have either provided only temporary relief or worsened the problem.
She typically gets 8 h of sleep at night. She never experiences these attacks while sleeping; however, they are often the last thing she experiences at night. She notes that on some days, relief only comes when she falls asleep, and she may retire early in an attempt to end the attacks.
Case 2
The second person to contact us was a 61-year-old woman from the USA. She is 1.65 m tall and weighs 96.5 kg. Her medical history includes the removal of one ovary, she has had her veins stripped twice in her left leg, a herniated disc, alpha 1 -antitrypsin deficiency, and has had carpal tunnel surgery on her right hand. Her blood pressure is normal and she takes Lipitor for high cholesterol.
Her chronic yawning bouts began 3 years ago, and she sought medical assistance 6 months after the onset. She has been to two general practitioners and two neurologists, but has not been offered a diagnosis for her condition, with multiple sclerosis, Parkinson's disease, and Lou Gehrig's disease all being ruled out. She has had two MRIs with no evidence of abnormality. She has not been prescribed any medication for her condition.
She gets 7-8 h of sleep at night and does not report feeling tired during the day. She sometimes experiences the onset of negative symptoms prior to sleeping and reports having woken up in deep sleep to a yawn attack. She took part in a sleep study and was diagnosed with sleep apnea but not narcolepsy. She was given a continuous positive airflow pressure machine (CPAP) for treatment of apnea. She reports an improvement in sleep following the use of the device, but her yawning attacks have not changed.
Both of their symptoms are very similar. Each complains of unpredictable and uncontrolled yawning attacks lasting from 5 to 45 min. During these excessive yawning episodes, they experience deep, recurrent, overwhehning yawns that cause their eyes to water and nose to run. Occurring one to 15 times a day, these attacks are very aversive and debilitating, and both patients report feeling ill and exhausted following an attack. The most common diagnosis is a sleep disorder, although neither patient reports sleep problems.
These cases include features consistent with a diagnosis of thermoregulatory dysfunction. Both patients report that nasal breathing and/or applying cool cloths to the forehead can provide temporary relief and/or postpone the onset of an attack. These effects are consistent with evidence that nasal breathing and facial cooling reduce brain temperature (9,10), and research has shown that nasal breathing and forehead cooling diminish the incidence of yawning [6). Taking a cold shower or swimming in cold water after the onset of an attack produces complete remission of symptoms for the South African woman. Both patients report feeling cold during or after an attack and experience goose bumps and shivering which may be a consequence of overcompensation by cooling mechanisms activated during thermoregulatory dysfunction. Each patient has also noticed that eating a large meal increases the likelihood of an attack. One obvious effect of food ingestion is to divert blood to the stomach and small intestine, which may occur at the expense of sending cooler blood from the periphery to the brain and compromise brain cooling as a result.
The woman from the USA can anticipate the onset of these yawning episodes and has taken oral measurements of her temperature using a digital thennometer (nearest 0.1°C) at the beginning and after a number of attacks. Her average temperature at the start of an attack was 37.5'C, compared with 37.1°C after an attack (Wilcoxon signed-ranks test, Z=-2.194,p=0.03), and her body temperature went down in nine out of ten instances (sign test, p=O.O2). The other woman has taken a variety of different medications, but none have provided consistent long-term relief. At one point, she was given modafinil (Provigil), prescribed for patients with narcolepsy, but it made her attacks more severe. This is particularly interesting because modafinil has been shown to elevate core temperature and impair cooling responses [11].
Contrary to popular opinion, yawning is not related to blood levels of oxygen or carbon dioxide [s1. Instead, growing evidence suggests that yawning acts as a thermoregulatory mechanism [6, 7). According to this model, increases in facial and cerebral blood flow following a yawn operate like a radiator, removing hyperthermic blood from the face and head, while introducing cooler blood from the lungs and extremities.
These cases suggest that excessive yawning is not indicative of a sleep disorder, and instead include features consistent with a diagnosis of thermoregulatory dysfunction.
The woman from the USA was diagnosed with sleep apnea, yet this was corrected with a CPAP, and her yawning persists. The same woman reports a significant reduction in body temperature following a bout of yawning, and the other reports that her symptoms were exacerbated while taking drugs shown to elevate core body temperature. In addition, both women report that nasal breathing and forehead coohng provide symptom relief and/or postpone the onset of an attack.
These findings suggest that the trigger for excessive yawning may be due to increases in brain and/or body temperature. That excessive yawning may be symptomatic of abnormal thermoregulation is also supported by bouts of excessive yawning in patients with thennoregulatory disorders (e.g., multiple sclerosis, epilepsy, or migraine headache) (7). Likewise, drugs that increase brain temperature frequently produce excessive yawning (e.g., SSRIs), while drugs that lead to hypothermia inhibit yawning (e.g., opioids) (7).
In summary, patients with symptoms of excessive yawning may experience debilitating side effects and should not be belittled nor should theft symptoms be trivialized. The applications of this research range from basic physiological understanding to using symptoms of excessive yawning as a diagnostic tool for identifying instances of thermoregulatory dysfunction. This evidence has the potential to provide important insight to sleep medicine and may clear up misconceptions regarding excessive yawning and sleep disorders. Further research needs to investigate the relationship between excessive yawning, body temperature, and the ability to effectively deal with heat stress. To this point, neither woman has been accurately diagnosed or effectively treated for theft condition; however, both have been notified of the possible connection to temperature regulation.
1. Baenninger R, Binkley S, Baenninger M Field observations of yawning and activity in humans. Physiol Behav 1996;59:42:1425.
2. Provine RR, Hamernik HB, Curchaek BB Yawning: relation to sleeping and stretching in humans. Ethology 1987;76:152-160
3. Zilli I, Giganti F, Salzarulo P. Yawning in morning and evening types. Physiol Behav 2007;91:218-222.
4. Provine RR Yawning. Am Sci 2005;93:532-539.
5. Provine RR, Hamernik HB, Curchack BB Yawning: no effect of 3-5% C02, 100% C02, and exercise. Behav Neural Biol 1987;48:382-393
6. Gallup AC, Gallup GG Jr Yawning as a brain cooling mechanism: nasal breathing and forehead cooling diminish the incidence of contagious yawning. Evol Psychol 2007;5:92-101
7. Gallup AC, Gallup GG Jr Yawning and thermoregulation. Physiol Behav 2008;95:10-16.
8. Gilbert 55, van den Heuvel CJ, Ferguson SA, Dawson D Thermoregulation as a sleep signally system. Sleep Med Rev 2004;8:81-93.
9. Hanis BA, Andrews PJD, Murray GD Enhanced upper respiratory tract airflow and head fanning reduce brain temperature in brain-injured, mechanically ventilated patients: a randomized, crossover, factorial trial. Br J Anaesth 2007;98:93-99.
10. Zenker W, Kubik S Brain cooling in humans--anatomical considerations. Anat Embryol (Berl) 1996;193:1-13
11. Launay JC, Besnard Y, GuinetA, Bessard G, RapheiC, Savourey G Effects of modafinil on heat thermoregulatory responses in humans at rest Can J Physiol Pharmacol 2002;80:796-803
Andrew C. Gallup. Yawning and the thermoregulatory hypothesis

mise à jour du
3 octobre 2010
12 septembre 2010
Sleep Breath.
Yawning and thermoregulation
Hannu Elo
Faculty of Pharmacy, University of Helsinki, Finland
Letter to the editirs
Dear Editors,
The paper "Excessive yawning and thermoregulation: two case histories of chronic, debilitating bouts of yawning" by Gallup and Gallup [1] deals with an interesting and potentially important topic. Yet, there are problems concerning it.
The patients never met the investigators, only providing subjective reports. On the basis of the two cases of pathological yawning that may be etiologically unrelated, conclusions are drawn concerning yawning in general.
The medical histories contain contradictions, and no details are given concerning blood tests and MRI investigations. Both patients are reported to suffer from excessive yawning in the absence of sleep problems. Yet, both had received sleep-related diagnoses (patient 1 received diagnoses of narcolepsy and excessive daytime sleepiness-and the same diagnoses were ruled out, and patient 2 was diagnosed with sleep apnoea).
A high fasting insulin level (patient 1) does not confirm insulin resistance and could result from insulinoma that causes life-threatening hypoglycaemias and would explain the symptoms (inability to walk, feeling ill, and extreme discomfort) and diagnoses (seizure, migraine, and excessive daytime sleepiness) [2-4]. It is not revealed which drug(s) worsened the problem. Metformin worsens hypoglycaemias [5].
The alpha-1-antitrypsin deficiency of patient 2 is important (often related to emphysema/COPD) [6], but this goes unnoticed, and the focus is solely on the putative thermoregulatory role of her yawning. No attention is paid to her obesity and its consequences. It is not always possible to exclude multiple sclerosis at an early stage.
Both patients should be encouraged to seek medical assistance. It is not sufficient that they have been "notified of the possible connection to temperature regulation".
The only measurements were performed by one patient under uncontrolled conditions and using uncontrolled methodology (no details given). Oral temperatures do not necessarily reflect core or brain temperature. What exactly is meant by saying "at the beginning and after a number of attacks" is not told, or how attacks were chosen for measurement. Subjectivity may have played a marked role, especially as the patient "can anticipate" the episodes. How she anticipates them is not reported. No conclusions should be based on these sporadic measurements.
A 0.4°C decrease of body temperature of a 96.5-kg patient requires the loss of 137 kJ of heat (specific heat capacity of the body 3.56 kJ kg-1 K-1 [7]). During a 5-min bout, the body would thus act as a 460-W heater capable of heating 430 ml of water from 25°C to the boiling point in 5 min (specific heat capacity of water 4.19 kJ kg' K' [7, 8]). With 15 daily bouts, the extra loss of heat is over 2,000 kJ, and if not compensated for by increased heat production, severe hypothermia will result (6°C decrease daily). If compensated (without extra eating), the increased metabolism will lead to a loss of more than 2 kg of body fat in a month. The obesity of the patient is not in accord with this. Compensation by drinking hot liquids (50°C) would require a daily consumption of ca. 38l .
There are few mechanisms by which the body can lose heat so that its temperature decreases:
1. Direct heat exchange with the environment (conduction to air, cloths, etc.)
2. Evaporation of water (lungs/airways, skin, and mucous membranes)
3. Thermal radiation
Yawning hardly directly affects thermal radiation (that depends only on the temperature and surface properties) or conduction of heat from the skin to the environment. It may increase air flow to the lungs, but even with maximal conductive loss (thermal equilibrium with the inhaled air), the amount lost is minimal, since the specific heat capacity and density of air are low [9]. Assuming ambient air of 25°C, the 0.4°C decrease requires inhalation of over 9,000 l of air. Thus, this mechanism cannot account for the temperature decreases.
Evaporation of water from the airways/lungs causes a maximal heat loss when the inhaled air is water-free. At 37°C, a loss of 137 kJ requires the extra evaporation of 57 g of water (heat of vaporisation 2,410 kJ kg-1[10]). Since the vapour pressure of water at 37°C is 47.1 mmHg [11, 12], the loss of 137 kJ requires inhalation and saturation of 1,380 l of dry air. With air that is already saturated with water at 25°C, 2,797 l must be inhaled. In the dry-air case, assuming exhalation of the maximum possible amount (3.6 l for a female) on every expiration, 383 inspirations are needed. With 15 expirations per minute, this takes 25 min. In the more realistic humid-air case, the process takes 52 min. (We have, for simplicity, neglected the fact that also normal breathing removes water vapour, and thus the extra removal of 137 kJ requires still far larger volumes.)
Furthermore, breathing with the maximal vital capacity for a long time causes severe respiratory alkalosis, unconsciousness, and death. So, this mechanism cannot explain the results. Water vapour can be lost also through sweating. This is the only explanation, if yawning indeed markedly decreases body temperature, and requires the extra evaporation (in addition to normal perspiration) of 57 g of sweat on each bout of yawning (850 ml with 15 bouts) and must lead to increased thirst and water intake that were not reported. Deceleration of the body's heat production (decrease of metabolic rate) may indirectly decrease body temperature. With a consumption of food equivalent with 2,100 kcal per day, a complete stop of metabolism (which would kill the patient) would have to continue for 23 min for each 0.4°C decrease of body temperature, assuming normal perspiration (impossible without metabolism!). If metabolism decreases by 25%, ca. 1.5 h will be needed for each bout of yawning. Even with a 3,000-kcal diet, each deceleration (100% or 25%) of metabolism would have to continue for 15 min or 1 h, respectively.
Thus, the reported decreases of body temperature during yawning are physically possible only if yawning effectively increases perspiration. The thermoregulatory hypothesis is interesting, and hypotheses are needed&emdash;but they should be called hypotheses or theories, not conclusions or results, as long as convincing evidence is missing.
1. Gallup GG, Gallup AC. Excessive yawning and thermoregulation: two case histories of chronic, debilitating bouts of yawning. Sleep Breath. 2010;14:157-159
2. Graves TD, Gandhi S, Smith SJM, Sisodiya SM, Conway GS Misdiagnosis of seizures: insulinoma presenting as adultonset seizure disorder. J Neurol Neurosurg Psychiatry 2004;75:1091&endash;1092.
3. Chin S, Popat V, Boyne MS, Cochran C, Tulloch-Reid M Insulinoma induced hypoglycaemia in a Jamaican patient. West Indian Med J. 2007;56:182&endash;186
4. Ebady S, Arami M, Kucheki E. A case of insulinoma with neuropsychiatric symptoms and cerebral infarction.
Internet J Neurol 2005;4(2).
5. Omari A, Yue DK, Twigg SM Exercise, metformin and hypoglycaemia: a neglected entity. Brit J Diabetes Vascular Dis 2005;5:106&endash;108.
6. Fregonese L, Stolk J Hereditary alpha-1-antitrypsin deficiency and its clinical consequences. Orphanet J Rare Dis 2008;3:16.
7. Koehler KR
8. Nordling C, Österman J (2004) Physics handbook for science and engineering, (10th printing, 2007), 7th edn. Studentlitteratur, Lund, p 39
9. McQuillan FJ, Culham JR, Yovanovich MM (1984) Properties of dry air at one atmosphere, Report "UW/MHTL 8406, G-01", Microelectronics Heat Transfer Lab, University of Waterloo, Waterloo, Ontario, Canada.
10. Bray JJ, Cragg PA, Macknight ADC, Mills RG (2003) Lecture notes on human physiology, 4th edn. Blackwell Publishing, Oxford
11. Wagner W, Pruss A International equations for the saturation properties of ordinary water substance. Revised
according to the international temperature scale of 1990. J Phys Chem Reference Data 1993; 22:783&endash;787
12. Oklahoma State University, Department of Chemistry (2010) Vapor Pressure of Water

mise à jour du
12 septembre 2010
Sleep Med
Yawning cannot cause significant
temperature decreases in humans
Hannu Elo
University of Helsinki, Faculty of Pharmacy
To the Editor,
In their paper on yawning in multiple sclerosis (MS), Gallup et al. [1] advocate their theory [2-4], according to which the physiological function of yawning is cooling of the brain and/or body. Without a trace of convincing evidence, the authors state that yawning is ''involved in thermoregulation. " A main piece of ''evidence" for the Gallup theory is constituted by a few measurements carried out (without controlled conditions or methods) by one patient who ''anticipates" her yawning attacks [2].
I have shown by calculations [5] that the temperature decreases claimed to occur during those attacks are physically impossible. In fact, any significant decrease of body temperature as a result of a few yawns is physically impossible except if yawning causes massive sweating. The same is true of any significant cooling of the brain, taking into account the following potential cooling mechanisms: evaporation of water (lungs/airways), conductive heat losses, thermal radiation, and deceleration of metabolism.
Gallup et al. state that ''increases in facial blood flow resulting from a yawn" remove ''hyperthermic blood from the face and head, while introducing cooler blood from the lungs and extremities. " There is no evidence for such ''hyperthermic blood" or such temperature differences. A ''sense of gratification" caused by yawning by no means constitutes evidence for the claimed homeostatic function of yawning.
Gallup et al. summarize: ''Growing evidence suggests that yawning may be a useful diagnostic tool for identifying thermoregulatory problems. " However, there is no evidence (not to mention growing evidence) for this claim. Unscientific claims in a clinically oriented journal may have potentially dangerous consequences.
The authors should pay attention to scientific reasoning and distinguish hypotheses from results, conclusions, and facts. If yawning relieves MS symptoms, the mechanism might be constituted by effects on the autonomic nervous system and/or release of hormones.
[1] Gallup AC, Gallup Jr GG, Feo C. Yawning, sleep, and symptom relief in patients with multiple sclerosis. Sleep Med 2010; 11:329&endash;30.
[2] Gallup GG, Gallup AC. Excessive yawning and thermoregulation: two case histories of chronic, debilitating bouts of yawning. Sleep Breath 2010; 14:157&endash;9.
[3] Gallup AC, Gallup Jr GG. Yawning and thermoregulation. Physiol Behav 2008; 95:10&endash;6.
[4] Gallup AC, Gallup Jr GG. Yawning as a brain cooling mechanism: nasal breathing and forehead cooling diminish the incidence of contagious yawning. Evol Psychol 2007; 5:92&endash;101.
[5] Elo H. Yawning and thermoregulation. Sleep Breath

mise à jour du
26 décembre 2010
Sleep Med
The thermoregulatory hypothesis of yawning: Time to reconsider terms such as "impossible" and "cannot" and evaluate theories based on evidence

Andrew C. Gallup

Response from the author:
Without significant evaluation of the original paper describing yawning and symptom relief in patients with multiple sclerosis, Elo attempts to undermine growing convergent support for the thermoregulatory hypothesis of yawning by simply reiterating comments made from a previous critique. In each case, Elo is uninformed, unscientific, misleading, and inaccurate when describing past research in this area.
His main contention is that by his 'calculations", yawning "cannot" produce significant changes in temperature, and that such changes are "impossible" without "massive sweating." However, his conclusions are untenable since the "calculations" refer solely to changes in overall body temperature, and not to localized changes in specific areas relevant to yawning (i.e., neck, face, and head). In fact, Elo's position is completely contrary to recent research where we directly investigated the relationship between yawning and brain temperature changes in rats.
Using implanted thermocoupled temperature probes in the prelimbic cortex, continuous measures of brain temperature were coupled with video-recorded sessions to track yawns and other behaviors. Results show yawning was preceded in all instances by rapid increases in brain temperature, accompanied by correspondingly consistent decreases in brain temperature and a return to baseline following each yawn. Furthermore, analyses show that similar decreases in brain temperature did not occur outside yawning and stretching events. Therefore, it is time to reconsider the use of blanket terms such as "impossible" and 'cannot" and begin evaluating theories based on evidence.
As for the paper on yawning and symptom relief in patients with multiple sclerosis, the results remain entirely consistent with the view that yawning may provide temporary mitigation of symptoms through a cerebral cooling effect. An appended table summarizes current evidence supporting the thermoregulatory hypothesis of yawning.