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and are sometimes associated with temporary dips in oxygen saturation
(Engleman & Joffe, 1999). It has been estimated that 2% of
women and 4% of men in the middle-aged workforce meet the diagnostic
criteria for OSAHS (Young et al., 1993).
Risk factors
One of the principal risk factors associated with OSAHS is obesity
(Vgontzas et al., 1994; Young et al., 1993). About half of all patients
with OSAHS are clinically obese, with body mass indexes (BMI)
exceeding 30 (Douglas, 2002). Obesity in conjunction with craniofacial
abnormalities is also associated with OSAHS (Ferguson et al.,
1995; Lofaso et al., 2000). Craniofacial abnormalities include small
upper airway, large tongue, large uvula, recessed chin, enlarged
tonsils and/or soft palate. Individuals who are habitual snorers generally
have a higher prevalence of apnoeas/hypopnoeas (Young
et al., 1993). There is a tendency for OSAHS to run in families and
there is data suggesting that the pathophysiology of SDB including
OSAHS may have a genetic basis, which could explain the familial
aggregation (Gaultier & Guilleminault, 2001). Lifestyle factors can
also have an effect on OSAHS. In a sample of men with mild to
moderate OSAHS even a relatively small consumption of alcohol
significantly increased apnoea frequency (Scanlan et al., 2000) (see
also ‘Obesity’).
Assessment of OSAHS
A diagnosis of OSAHS can be easily missed unless patients present
with sleepiness plus snoring as the primary complaint. Patients with
possible OSAHS are generally investigated by performing overnight
sleep studies (polysomnography) to assess breathing activities
during sleep (Douglas, 2002). The main components of polysomnography
are the electro-encephalograph (EEG), which determines
whether the patient is awake or asleep. Electro-oculograph (EOG),
electro-myograph (EMG) and electro-cardiogram (ECG) determine
sleep stage, arousals and cardiac function. Airflow obstruction can
be determined by plethysmorgraphy, which measures rib cage and
abdominal movement or by thermistor assessment of oronasal airflow.
Arterial oxygen saturation is often monitored using pulse oximetry
(Shneerson, 2000).
Daytime sleepiness can be assessed using objective and subjective
measures of sleepiness. Objective measures include the
Maintenance of Wakefulness Test (MWT) (Mitler et al., 1982). This
involves patients lying in a quiet darkened room where they are
instructed to stay awake. Sleep onset latencies are calculated from
the time the room is darkened until the appearance of the first
30-second epoch of any stage of sleep measured by a polysomnograph.
There is also a behavioural modification of the MWT known
as the Oxford Sleep Resistance Test (OSLER) (Bennett et al., 1997),
where the patients press a button in response to a small light when it
flashes. The test terminates when a patient fails to respond to the
light seven times consecutively (indicating sleep onset) or after
40 minutes. One of the most frequently used self-report measures
is the Epworth Sleepiness Scale (ESS), which asks patients to rate the
likelihood of themselves dozing off in a variety of situations (Johns,
1993) (see also ‘Sleep and health’).
Treatment
Initially treatments are aimed at relieving the patients’ symptoms.
Recommendations may include weight loss, reducing alcohol consumption,
avoiding benzodiazepines and other hypnotic drugs,
avoiding sleep deprivation, positional treatment (sleeping on the
side rather than in a supine position), improving the nasal airway
with inhaled steroids or nasal dilators and smoking cessation
(Schneerson, 2000). Secondary treatments are reserved for patients
who have more frequent and severe OSAHS that does not respond to
initial treatments, either because they are ineffective or due to poor
adherence (Schneerson, 2000). Patients with mild OSAHS may be
treated with REM sleep suppressants such as antidepressants,
which can be effective if OSAHS is mostly confined to REM sleep.
Patients with moderate to severe sleep apnoea may be offered
continuous positive airway pressure (CPAP), mechanical devices
or surgery (Schneerson, 2000).
CPAP therapy is the treatment of choice for most patients
(Douglas & Engleman, 1998). This involves patients wearing a face
mask at night, while air is pumped in and maintained at a fixed
level. CPAP acts by raising the pressure within the upper airway to
a sufficient level to prevent occlusion (Douglas, 2002). Evidence
suggests that CPAP is an effective treatment for OSAHS (Ballester
et al., 1999; Engleman et al., 1994; Engleman et al., 1998; Jenkinson
et al., 1999). Mandibular repositioning splints are designed to keep
the lower jaw protruded during sleep, thus preventing the tongue
falling back and narrowing the throat. Currently mandibular repositioning
splints are used for patients with mild to moderate sleep
apnoea who do not tolerate CPAP (Douglas, 2002). There are numerous
surgical treatments for OSAHS designed to cure rather than
control the problem. The most commonly performed surgical procedure
is uvulopalatopharyngoplasty but there remains a need for
carefully conducted research to establish the efficacy of this procedure
(Douglas, 2002).
Nocturnal features of OSAHS
The most common clinical feature of OSAHS is loud snoring that
can exceed 65 dB (Guilleminault, 1994), similar to that of pneumatic
drills or motorbikes (Douglas, 2002). Most OSAHS patients report
that they wake unrefreshed yet believe that they sleep fairly soundly
and are unaware of the recurring arousals from sleep, which are too
transitory to be recalled (Douglas, 2002). Patients may also report
restlessness during the night, which is reflected by increased tossing
and turning with a proportion displaying more agitated behaviour
with gross movements of the arms and legs (Guilleminault, 1994).
Some patients also awaken with a feeling of choking or gagging and
report being unable to breathe for several seconds resulting in panic
before being able to breathe again (Douglas, 2002). Nocturia is a
frequently reported problem, with as many as four to seven nightly
trips to the bathroom being reported by 28% of OSAHS patients
(Guilleminault, 1994).
Daytime consequences of nocturnal events
The diagnosis and therapy for OSAHS focus on the nocturnal features
of the condition, but it is the daytime consequences of these