Sleep Lab.
Dept. of Psychology - University of Florence,
Firenze, Italy
Yawning is a behaviour
beginning in the first epochs of life. It has
been observed not only in infants and in
newborns, but also in foetuses of 12-14 weeks of
gestational age.
Yawning frequency changes
across the life span. In preterm infants the
number of yawns decreases between 31 and 40
weeks of post-conceptional age, mainly during
the day. In this period of life yawn is an
isolated behaviour rarely occurring in burst and
its the frequency is quite low with respect to
the adult.
The incidence of yawns
seem increase when children attend the
elementary school, whereas in the elderly the
number of yawns is reduced. Aged subjects yawn
less than young people mainly during morning and
mid-afternoon hours. As in the adult also in the
elderly the time course of yawning is associated
with the time course of sleepiness excepted at
the awakening when the high frequency of yawns
is not associated to high
sleepiness.
Both in the adult and in
the elderly yawning frequency increases in the
early morning and in the late evening, whereas
at the earliest stages of development (foetuses
and preterm infants) yawns do not show diurnal
variations.
Yawning seem to be
involved in the modulation of arousal process
across the whole life span. In preterm infants
yawning is often followed by motor activation
and it is more common during the waking than
sleep; in the adult and in the elderly yawning
occurs mainly at the sleep onset and at the
awakening.
