BACKGROUND: Patients with multiple
sclerosis (MS) suffer from thermoregulatory
dysfunction, and repetitive yawning and sleep
problems are symptoms of MS. Because yawning and
sleep are involved in thermoregulation, we
investigated the association between yawning,
sleep, and symptom relief in patients with
MS.
METHODS: Sixty patients filled out a
questionnaire about how often they yawned,
whether yawning provided relief of MS symptoms,
and how sleep affected these symptoms.
RESULTS: Results showed that over one
in three patients reported that their MS
symptoms improved following a yawn, and of those
experiencing relief, nearly half reported that
it lasted for several minutes or longer. Not
getting a good night's sleep often made MS
symptoms worse, while napping during the day
provided symptom relief.
CONCLUSION: This is the first study
showing that yawning provides symptom relief in
patients with multiple sclerosis
Introduction
Multiple sclerosis (MS) involves
thermoregulatory dysfunction, with heat making
symptoms worse and cooling often providing
symptom relief. Frequent yawning is associated
with a number of conditions, drugs, and diseases
linked with heat stress or abnormal
thermoregulation, including MS.
Contrary to popular opinion, yawning is not
affected by changes in blood oxygen or carbon
dioxide levels. Instead, recent research
suggests that yawning is triggered during rises
in brain and/or body temperature and may act as
a brain cooling mechanism. 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
produced by a yawn are similar to those that
promote cerebral cooling. As evidence for its
beneficial homeostatic function, yawning often
produces a brief sense of gratification in
healthy populations. Yawning also follows a
circadian pattern occurring most often before
and after sleep, and sleep problems are
experienced by patients with MS. In this study
we investigated self-reported effects of yawning
and sleep on MS symptoms.
Discussion
This is the first report that yawning
provides symptom relief among patients with MS.
Over one of every three patients reported that
their MS symptoms were better following a yawn,
and among those who reported feeling better,
nearly half reported that this lasted for
several minutes or longer.
Although we did not collect data regarding
the specific nature of MS symptom relief
associated with yawning, based on informal
communication with some patients the relief can
amount to temporary periods in which patients
experience almost complete remission of MS
symptoms. It should be noted that while the
hedonic properties of a yawn have previously
been reported in normal individuals, these
effects are fleeting and short-lived. Thus, the
more durable effects on symptom relief that we
found appear specific to MS patients.
Not getting a good night's sleep made MS
symptoms worse for many patients. Likewise,
napping during the day provided symptom relief
for nearly two-thirds of the patients.
Interestingly, these individuals also reported
yawning more often each day. Taken together,
these findings are consistent with previous
reports showing a high frequency of sleep
problems associated with MS and support the idea
that yawning may be a brain cooling mechanism
because sleep and body temperature vary
inversely. Patients reported heat, fatigue, and
stress as the most common factors making their
symptoms worse, all of which are associated with
increased body temperature.
Conversely, most patients reported that
leisure and methods of cooling provided the
greatest relief. It is interesting that cooling
of the head and neck has been shown to alleviate
MS symptoms, and forehead cooling blocks
yawning, supporting the view that yawning may
provide a temporary brain/cerebral cooling
effect. One limitation to this study is that the
survey questions did not identify the specific
relief from MS produced by yawning. Thus,
further research is needed to examine these and
other relationships. But the current report
provides an initial step in investigating the
potential alleviatory effects of yawning in
patients suffering from MS.
Recent research has provided additional
evidence of an association between MS and
cerebral thermoregulatory dysfunction, showing a
strong connection between MS and chronic
cerebrospinal venous insufficiency. Thus, we
propose that enhanced facial and cerebral blood
flow resulting from a yawn may act to overcome
the altered modality of venous return in MS
patients, providing temporary circulation of
cooler blood to the brain and ultimately
providing short-term remission of MS symptoms.
Overall, the findings presented indicate yawning
deserves further investigation in clinical
studies of patients suffering from different
forms of thermoregulatory dysfunction. Growing
evidence suggests that yawning may be a useful
diagnostic tool for identifying thermoregulatory
problems.
Myelin
sheath: A new possible role in sleep mechanism
Alessandro Morelli Silvia Ravera
Isabella Panfoli
Department of
Biology, University of Genoa,
Italy
Sleep Medicine 12 (2011)
198&endash;199
Myelin sheath, the multilayered membrane
produced by oligodendrocytes, plays a pivotal
role in the surrounding axon, allowing the nerve
to transmit its impulses rapidly. But there is
growing evidence that myelin has also an
unexplained neurotrophic role. We reported that
the respiratory chain components are expressed
in myelin, outside of mitochondria [1].
These components would generate a proton
gradient across myelin membranes to support
adenosine triphosphate (ATP) synthesis by an
F0&endash;F1 ATP synthase. This may explain how
in demyelinising diseases, like Multiple
Sclerosis (MS), myelin loss causes an axonal
necrosis.
Recently, Gallup et al. [2]
described sleep problems and frequent yawning in
MS patients. During sleep, the glucose
consumption by the brain is very similar to that
in wakefulness, even though the neuronal
energetic demand is low. We have envisaged an
involvement of myelin sheath. Imagine that
myelin sheath acts as a proton (H+) buffer
capacitor, thanks to the abundance of myelin
basic protein (MBP) and phospholipids, whose
exceptional buffering capacity of phospholipids
was demonstrated [3]. This potential
would be used by myelin to produce energy during
the wake period. In turn, sleep would be induced
by a ''discharge'' of H+ in myelin sheath and
wakefulness by a ''complete recharge'' of myelin
sheath.
The sleep need correlates to age. In fact,
newborn and children have a higher sleep need
than adults. This may depend on myelinogenesis,
which begins after birth and proceeds until
about 22 years of age. Under these conditions,
myelin may be less competent in accumulating
energy i.e.: H+ and may generate the need for
sleep. Interestingly, sleep is also regulated by
oleamide, an endogenous hypnotic compound that
increases before sleep, decreases before wake
and is accumulated in cerebrospinal fluid of
sleep-deprived animals [4]. Oleamide
closes the myelin gap junctions, formed by
connexins 32 [5], that seems to
transport mainly ATP [6], likely from
myelin to the axon.
References
[1] Ravera S, Panfoli I, Calzia D,
Aluigi MG, Bianchini P, Diaspro A, et al.
Evidence for aerobic ATP synthesis in isolated
myelin vesicles. Int J Biochem Cell Biol
2009;41:1581&endash;91.
[2] Gallup AC, Gallup Jr GG, Feo C.
Yawning, sleep, and symptom relief in patients
with multiple sclerosis. Sleep Med
2010;11:329&endash;30.
[3] Grzesiek S, Dencher NA.
Dependency of delta pH-relaxation across
vesicular membranes on the buffering power of
bulk solutions and lipids. Biophys J
1986;50:265&endash;76.
[4] Basile AS, Hanus L, Mendelson
WB. Characterization of the hypnotic properties
of oleamide. Neuroreport
1999;10:947&endash;51.
[5] Altevogt BM, Kleopa KA, Postma
FR, Scherer SS, Paul DL. Connexin is uniquely
distributed within myelinating glial cells of
the central and peripheral nervous systems. J
Neurosci 2002;22:6458&endash;70.
[6] Goldberg GS, Moreno AP, Lampe
PD. Gap junctions between cells expressing
connexin 43 or 32 show inverse permselectivity
to adenosine and ATP. J Biol Chem
2002;277:36725&endash;30.
