One of the main goals of treatment for OSA is to control EDS.
Tracheostomy was the first effective treatment for OSA. However,
it is rather invasive. In 1981, the introduction of the Continuous
Positive Airway Pressure (CPAP) treatment by Sullivan
and his colleagues has marked an important milestone in the
management of OSA.
CPAP has been proven in many clinical trials to be efficacious
in normalising Apnoea-Hypopnoea Index (AHI) in OSA, as
well as in controlling EDS 2. CPAP is now the recommended
first-line treatment for OSA. However, there are certain
groups of OSA patients, who still have persistent sleepiness
after a CPAP usage.
The prevalence of sleepiness after CPAP was reported as 12%
and 6% after exclusion of all possible causes of sleepiness
in a French study 3. Another large French study also demonstrated
a prevalence of 13% 4.
It is important to establish the underlying cause of persistent
sleepiness in OSA patients while on CPAP.
Suboptimal CPAP treatment can lead to the inadequate
control of OSA. This can be due to:
Adherence to the CPAP is defined as a night use of
at least 4 hours, on at least 70% of nights. CPAP adherence
is quoted to be around 40% - 83% in many
The reasons for poor CPAP adherence are complex and
often multifactorial, including a CPAP intolerance. Many
studies have looked at various strategies to improve the
CPAP adherence. Systematic education and supportive
care, cognitive behavioural therapy and heated humidification
are the few proven effective measures that improve
the CPAP adherence.
The co-occurrence of PLMD and OSA varied from 47%
to 61.5% in different studies. Periodic Limb Movements
in Sleep (PLMS) can disrupt sleep by causing arousals in
sleep which in turn result in daytime sleepiness.
Classical clinical presentations include cataplexy, excessive
daytime sleepiness, hypnagogic hallucination and
sleep paralysis. Narcolepsy is divided into Type I (with
cataplexy/a CSF hypocretin deficiency) and Type II (without
cataplexy/a CSF hypocretin deficiency).
The Multiple Sleep Latency Test (MSLT), a biological test,
is used to help with the diagnosis of narcolepsy. In narcolepsy,
the MSLT shows a short sleep latency (< 8 minutes)
and ≥ 2/4 Sleep-Onset Rapid Eye Movements (SOREMs).
OSA is not uncommon in narcolepsy, with a reported
prevalence of up to 24.8% in one study 5.
Idiopathic Hypersomnia (IH)
Patients with IH present with excessive daytime sleepiness
despite the long hours of sleep (> 11 hours/day) and
IH is diagnosed by the exclusion of the other possible
causes of EDS. The MSLT shows short sleep latency (< 8
minutes) and < 2/4 SOREMs.
Behaviourally Induced Insufficient Sleep Syndrome
Patients with BIISS have a shorter habitual sleep episode,
than is expected from age-adjusted normative data.
When the habitual sleep schedule is not maintained (for
e.g., on weekends or during a vacation), they will sleep
for longer than is usual. A diagnosis can be made by taking
a good history, supported by a sleep diary and an
Patients with depression can present with daytime sleepiness.
Depression is common in OSA.
A study showed that 40% of untreated OSA patients had
some depressive symptoms and 2% had moderate to severe
depression 6. The presence of depression has been
shown to be one of the predictors of persistent sleepiness
after a CPAP 4.
Many medications have sedative effects, e.g., antihistamines,
analgesics, anticonvulsants and certain antidepressants.
The use of recreational drugs or alcohol can
be the cause of daytime sleepiness.
Chronic intermittent hypoxia during sleep in untreated
OSA may result in permanent damage to brain regions
involved in wakefulness. This insult may not be completely
reversed with CPAP treatment.
Obesity itself is an independent risk factor for hypersomnolence.
Many patients may perceive fatigue as sleepiness. Fatigue is not associated with the higher propensity to sleep but with
a feeling of exhaustion and lethargy and decreased activity.
It is important to take a good history, to differentiate between these two distinct symptoms. A good, detailed and thorough
history will help to identify the possible underlying cause for the persistent sleepiness, after CPAP.
TO OPTIMISE THE CPAP TREATMENT
Apart from a detailed history, the CPAP downloads provide useful information on the residual AHI, a mask
leak and the adherence.
In some cases, the CPAP downloads appear to be within the normal limits but if there is the clinical suspicion
of inadequately treated OSA, attended Polysomnography (PSG) while on CPAP should be considered.
RULE OUT BIISS
BIISS is a common cause of daytime sleepiness. Therefore, it is important to rule out BIISS by taking a
good history and by reviewing the sleep diary or the actigraphy.
IDENTIFY AND REVIEW THE INDICATIONS OF ANY MEDICATIONS THAT CAN CAUSE SLEEPINESS
Once the culprit medications that cause the sleepiness are identified, the sleep physician should liaise with
the prescribing physician to decide to either stop the medications if there is no clinical indication to continue,
or to switch to other non-sedative medications. Any recreational drugs or alcohol should be stopped.
LOOK FOR ANY CO-MORBID ORGANIC SLEEP PATHOLOGY AND TREAT ACCORDINGLY
PLMD, narcolepsy and IH can be diagnosed by taking a good history, and supported by performing a PSG
or MSLT, while on a CPAP.
TREAT ANY CO-MORBID MOOD DISORDERS
Treating co-morbid depression can reduce the sleepiness in OSA patients while on a CPAP.
TO CONSIDER THE USE OF MODAFINIL
Modafinil is licensed in the USA, for use in OSA patients who still have persistent sleepiness after the use
of a CPAP. It is a stimulant and the exact mechanism of action is yet to be ascertained.
Persistent sleepiness in OSA patients while on a CPAP is not uncommon. The possible underlying cause should be looked into
and managed accordingly before considering Pharmacotherapy (modafinil).
GPs can call for appointments through the GP Appointment Hotline at 6850 3333 for more information.
By: Dr. Wong Hang Siang, Consultant, Department of Respiratory and Critical Care Medicine, Changi General Hospital; SingHealth Duke-NUS Sleep Centre
Dr. Wong Hang Siang is a Consultant Respiratory and Sleep Physician at the Changi General Hospital. He
did his Sleep Fellowship training at the Guy’s Hospital, London and his Chronic NIV training at the Lane Fox
Respiratory Unit of St. Thomas’ Hospital, London. His area of clinical interests are in OSA, OHS and Chronic
NIV use in Chronic respiratory failure patients.
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2. Giles TL, Lasseron TJ, Smith BJ, et al. CPAP for OSA in adults. Cochrane Database Systematic Review 2006; Cd001106.
3. Pepin JL, Viot-Blanc V, Escourrou P, et al. Prevalence of residual excessive sleepiness in CPAP-treated sleep apnoea patients: the French
multicenter study. Eur Respir J 2009; 33: 1062-1067.
4. Gassa M, Tamisier R, Launois SH, et al. Residual sleepiness in sleep apnoea patients treated by CPAP. J Sleep Res 2013; 22: 389-397.
5. Sansa G, Iranzo A, Samantaria J. OSA in narcolepsy. Sleep Med 2010; 11: 93-95.
6. Vandeputte M, de Weerd A. Sleep disorders and depressive feelings: a global survey with the Beck depression scale. Sleep Med 2003;
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