This Medical Video:
Sleepiness, tiredness and fatigue are complaints which must be
thoroughly analyzed to eliminate blur and ambiguity.
sleepiness (“sleep pressure”) increases while being awake and
additionally underlies the circadian rhythm with a lower threshold
to fall asleep during night time.
Excessive daytime sleepiness
(EDS) is considered normal only after sleep deprivation. Clinically,
EDS manifests by frequents daytime napping and/or reduced alertness
with automatic behavior or - in its extreme form - in recurrent
attacks of sudden, uncontrollable compulsion to sleep also in
inappropriate situations ( “sleep attacks”).
“objectively” addressed by measuring the mean sleep latency to
four to five nap opportunities throughout the day using the multiple
sleep latency test (MSLT) or the maintenance of wakefulness test
EDS denotes both, a ready entrance into sleep as well as
difficulty in staying awake during daytime or accordingly in
inappropriate situations. These two partially independent aspects of
EDS are separately assessed by the “passive” MSLT and the
“active” MWT respectively.
For that reason the MSLT and MWT
only weakly correlate with each other when tested over a broad range
of patients with EDS. It is important to keep in mind, that these
tests are importantly influenced by a great variety of factors such
as mood, anxiety, and motivation.
wakefulness, alertness and attention and therefore is more than just
the reciprocal to sleepiness. Cognitive performance tasks such as
Steer Clear Reaction Time Test (SCRTT) or driving simulators require
the complete integrity of vigilance to achieve normal results.
Hypersomnia is usually broadly defined as the combination of
abnormally prolonged night-time sleep (regularly 10 h) with EDS
during ≥1 months.
On the other hand, the term hypersomnia has
also been used in a narrower scene for the isolated abnormality of a
prolonged night-time sleep need (10 h). “Tiredness”, also in
colloquial language often used for sleepiness, in a broader sense
also describes the feeling of lack of energy, motivation and
These patients seek rest rather than sleep. They
often cannot fall asleep when given the opportunity in spite of
feeling tired, and hence, in an MSLT, do not show an abnormally
short sleep latency. Furthermore, tiredness (and fatigue) as opposed
to sleepiness has a mental (“central”) and physiological (bodily
or “peripheral”) component, which the patients can readily
distinguish. Patients with insomnia, mild sleep apnea syndrome, or
depression rather suffer from mental tiredness than sleepiness
during the day.
The simple subjective self-assessment using the
Epworth Sleepiness Scale (ESS) quite reliably differentiates between
sleepiness and mental tiredness (without sleepiness), which makes it
a widely used test. The term “fatigue” is also heterogeneously
In physiology the “fatigue” implied a “time on task
performance decrement” to describe decreasing muscle force during
a sustained physical effort. In clinical medicine one distinguishes
physical (“peripheral”) from mental (“central”) fatigue and
the term usually denotes a chronic and more abnormal situation than
In a broad sense “fatigue” implies a deficiency in
coping satisfactorily with mental and physical work load. The
chronic fatigue syndrome entails both mental as well as a physical
fatigue (so called “leaden paralysis” of limbs). Depressive
states are often associated with insomnia and fatigue, but there are
also cases with hypersomnia rather than insomnia ( non organic
hypersomnia , “atypical depression” or “hypersomnolent
Sometimes these patients have a tendency to spend
much of the day lying in the bed without actually sleeping (so
called clinophilia). The basic and clinical aspects of fatigu