Giganti F, Guidi S, Ramat S, Zilli I,
Raglione LM, Sorbi S, Salzarulo P.
Department of Neurosciences,
Psychology, Drug research and Child health,
University of Florence, Italy
In healthy subjects, yawning usually occurs
with increasing sleepiness [1], possibly
in order to counteract low levels of arousal
[2]. Excessive daytime sleepiness is a
frequent complaint in patients with Parkinson's
Disease (PD) and sleepiness could be an initial
manifestation preceding other symptoms
[3,4]. As a consequence, PD patients
might experience an increase in yawning
frequency, mainly of yawning bursts, which are
an index of yawning production intensity.
We enrolled 18 untreated early stage PD
patients (F 1/4 9, M 1/4 9; age 1/4 68.39 1.89,
mean standard error) with 18 age-matched ( 3
years) healthy controls (F 1/4 9, M 1/4 9; age
1/4 67.22 1.98) [5]. All subjects signed
informed consent to participate in the study.
The study received institutional ethical
approval. Subjects were provided with a wrist
activity monitor (Actiwatch- Plus; Cambridge
Neurotechnology Ltd, Pampisford, Cambridge, UK)
to wear for three consecutive working days.
Throughout this period they were also required
to note each yawn by pushing an event marker
button placed on the top of the actiwatch and to
record in a personal log the time of onset of
any quick succession (two or more) yawns,
specifying the number of yawns. They were also
asked to evaluate their level of sleepiness
using the Karolinska Sleepiness Scale
[6]. The overall yawning frequency
(number of yawns per day/hour spent awake) was
compared between the two groups through oneway
ANOVA.
We analysed separately isolated yawning (IY)
and yawning bursts (YB); a yawing burst was
defined as a sequence of more than one yawn
occurring within a minute. The frequency of IY
and YB (the number of isolated yawns and of
bursts of yawning/hours spent awake) were both
compared between the two groups through one-way
ANOVA. The time-course of yawning (overall, IY,
YB) was assessed through ANOVA for repeated
measures, with "group" as the between factor,
"hour" as thewithin factor and "yawning" as the
dependent variable. For overall ANOVA
significant effects, differences between
subjects were evaluated using Student's t-test
for unpaired samples. Differences within
subjectswere tested separately for each group
applying an ANOVA for repeated measures with
"hour" as the within factor and "yawning" as the
dependent variable.
The results of rest-activity rhythm and
sleepiness have been reported in a previous
study [5]. The overall frequency of
yawns (number of yawns per hour) during the
awake period was higher in de novo PD patients
(0.69 0.11) compared to healthy control subjects
(0.49 0.09), although this difference failed to
reach statistical significance.
The frequency of YB was higher in de novo PD
patients compared to healthy control subjects
(F1,34 1/4 4.89, p < 0.05), whereas no
significant differences between the two groups
were observed in the frequency of IY.
The analysis of the time-course revealed
that the whole yawning frequency was higher in
de novo PD patients than in healthy control
subjects ("group": F1,331/44.79, p<0.05) and
it varied according with the time of the day
("hour": F15,495 1/4 5.33, p < 0.001).
Specifically yawning frequency peaked early in
the morning, during the afternoon and late in
the evening in both de novo PD patients ("hour":
F15,240 1/4 2.808, p < 0.001) and healthy
control subjects ("hour": F15,240 1/4 2.099, p
< 0.05), however at 2p.m. yawning was higher
in de novo PD patients than in healthy control
subjects (t 1/4 2.99, p < 0.01).
The number of IY varied across the awake
period ("hour": F15,495 1/4 3.13, p < 0.001)
in both groups, without significant differences
between the two. In particular, IY frequency
peaked early in the morning, during the
afternoon and late in the evening in both de
novo PD patients ("hour": F15,240 1/4 1.932, p
< 0.05) and healthy control subjects ("hour":
F15,240 1/4 2.602, p < 0.01). PD patients
performed more YB than healthy control subjects
("group": F1,33 1/4 7.01, p < 0.05) and the
YB frequency varied across the awake period
("hour": F15,495 1/4 3.55, p < 0.001). In de
novo PD patients YB frequency peaked early in
the morning, during the afternoon and late in
the evening ("hour": F15,240 1/4 2.224, p <
0.01), whereas in healthy control subjects YB
frequency did not change during the day.
Moreover, at 2 p.m., PD patients experienced
more YB than healthy control subjects (t 1/4
2.05, p < 0.05).
Our results showed that the circadian
distribution of yawning is not altered in
untreated patients with early-stage Parkinson's
disease, since the frequency of yawns was
similar throughout the awake period in both de
novo PD patients and in healthy controls. De
novo PD patients yawnedmore frequently than
healthy subjects, especially during the
afternoon, when the increase of sleepiness is
significant [5]. At that time, it is
mainly yawning occurring in bursts that accounts
for increased yawning frequency. One likely
hypothesis might be that a quick succession of
yawns represents the effort of PD patients
trying to remain alert and awake.
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