Assessment of Excessive Daytime Sleepiness (Causes,
consequences and differential diagnosis)
Centre de Médecine du Sommeil, Cliniques universitaires Saint-Luc, Université
catholique de Louvain, Bruxelles, Belgium
Sleepiness is a physiological state, with many facets. It is a subjective feeling related
to the need for sleep or the imminence of sleep, sometimes accompanied by
objective signs. It can also refer to a tendency to fall asleep or an intermediate state
between wakefulness and sleep. When excessive, it is a medical problem
often unrecognized as such by patient and thus underdiagnosed.
The assessment of excessive daytime sleepiness (EDS) is important for both the
diagnosis of underlying health problems and for gauging treatment response, but this
assessment remains a challenge. It begins with a precise history completed by a
sleep diary. Several tools have been developed to assess EDS more quantitatively
but each has shortcomings. Introspective behavioural scales query the individual’s
perception of sleepiness. The most widely used are the Stanford sleepiness scale
and the Epworth sleepiness scale. More objective tests rely on measurements of
physiological parameters. The most popular are based on polygraphy. The multiple
sleep latency test (MSLT) measures the tendency to fall asleep, whereas the
maintenance of wakefulness test (MWT) aims to measure the ability to stay awake.
Neither test correlates well with subjective measures of sleep such as the different
sleepiness scales. In recent years, there has been an effort to document EDS
associated with occupational risk, for instance with a driving simulator. However,
these laboratory-based tests may not reflect or predict real-life experience.
The most common cause of EDS is insufficient sleep due to poor sleep hygiene or
self-imposed or socially-dictated sleep restriction. Sleep fragmentation by repeated
arousals or awakenings is another cause of EDS. The most common cause of
fragmented sleep is obstructive sleep apnoea syndrome (OSA). Continouous positive
airway pressure, the treatment of choice for patients with moderate-to-severe OSA,
has been demonstrated to effectively improve subjective and objective sleepiness,
both in the laboratory and on the road. EDS is a common problem in patients
submitted to circadian desynchronisation, for instance night or shift workers. EDS is
associated with a wide number of medical, neurologic and psychiatric conditions.
Narcolepsy is a chronic disease, associated with severe EDS. Numerous drugs
Awareness of the consequences of EDS and its implications for public health and
safety is increasing. EDS impairs the entire spectrum of mental abilities, ranging from
simple psychomotor tasks to executive performance and is a major cause of
accidents in transport and industry. Today, different driving license regulations in
various countries try to decrease the risk of motor vehicle crashes in patients with
OSA. The occupational risks associated with EDS have also been well documented
in medical practice and have led to a work-hour reduction in medical residency.
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