Insomnia Insomnia
Insomnia Insomnia
Insomnia Insomnia
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142 Duntley<br />
disorders has been confirmed, although the clinical significance of this relationship<br />
continues to be defined.<br />
EPIDEMIOLOGY<br />
The epidemiology of insomnia in sleep disorders is dependent on the epidemiology<br />
of the primary sleep disorder itself. One community-based population study<br />
found about 2% of women and 4% of men have OSA syndrome (4). A recent university-based<br />
study of patients with sleep-disordered breathing found that of 231<br />
patients sampled, 116 complained of clinically significant insomnia (5). Among<br />
postmenopausal women complaining of insomnia, 83% were noted to have upper<br />
airway resistance syndrome (UARS) or OSA syndrome (6). <strong>Insomnia</strong> complaints<br />
in patients with OSA syndrome, like insomnia complaints in general, may be more<br />
frequent among women than men (7). Central sleep apnea syndrome is less common<br />
than OSA, but patients appear to be less likely to report daytime hypersomnolence<br />
and more likely to complain of insomnia (8). RLS is common, with a recent<br />
population-based study revealing bedtime symptoms in 10–15% of individuals (9).<br />
Difficulty falling asleep was reported by 84.7% of patients and 86% reported frequent<br />
awakenings with difficulty falling back asleep because of symptoms (10).<br />
PLMD increases with age, being uncommon before 30 years of age, seen in 5% of<br />
individuals between 30 and 50 years of age, and in about 44% of individuals aged<br />
65 and older (11). One multicenter study found PLMD to be the primary diagnosis<br />
in 17% of patients complaining of insomnia (12). Narcolepsy has a prevalence of<br />
about 0.05% (13). Fragmented sleep is found in up to 90% of patients with narcolepsy<br />
(14) and tends to be relatively mild initially, increasing in severity over time<br />
(15). Nightmares with a frequency of once a week or greater are seen in 4% of the<br />
adult population in Austria (16). One study in France found that 18.3% of insomnia<br />
patients were diagnosed as having nightmares (17). Occasional sleep starts are a<br />
nearly universal phenomenon. Sleep starts may rarely become repetitive at sleep<br />
onset resulting in sleep-onset insomnia.<br />
ETIOLOGY<br />
The cause of insomnia varies according to the primary sleep disorder, and may<br />
result from the sleep-onset and maintenance difficulties inherent in the disorder<br />
itself or from secondary symptoms of the disorder. For instance, in OSA syndrome,<br />
the termination of the apnea is associated with an arousal or awakening that may be<br />
perceived and remembered by the patient. OSA syndrome is also associated with<br />
other symptoms, such as nocturia and dry mouth, which can contribute to the development<br />
of an insomnia complaint. In RLS, the dysesthesias and need to move the<br />
legs prevents sleep onset, and may prevent returning to sleep after awakenings in<br />
the middle of the night. In PLMD, limb movements are associated with arousals or<br />
awakenings that may lead to the perception of difficulty initiating or maintaining<br />
sleep. In narcolepsy, the neurochemical defect leads to dysregulation of sleep