Many Americans suffer from insomnia regularly, but clinicians often do not address this issue. A variety of factors may contribute to insomnia, including medical conditions such as gastroesophageal reflux disease, Parkinson disease, and heart failure. Medications such as amphetamines, theophylline, and beta agonists could also precipitate insomnia.
Insomnia is a disorder of sleep characterized by the inability to fall asleep or stay asleep, early awakening, or nonrestorative sleep. A recent National Institutes of Health (NIH) State-of-the-Science Conference Statement on chronic insomnia defined insomnia as "complaints of disturbed sleep in the presence of adequate opportunity and circumstance for sleep."1 Many factors can affect a person's ability to sleep; sleep disorders are frequently multifactorial.
Insomnia affects approximately 50% of patients seen in primary care practices in the United States; 20% of these patients have chronic insomnia and only 30% of all patients sleep well.1 According to the NSF, 54% of adults have 1 symptom of insomnia a few times per week, and 33% of these patients have ≥1 symptom almost every night.1 The NSF has estimated that approximately 70 million adult Americans have some symptom(s) of insomnia.1 Insomnia may affect individuals aged ≥65 years more frequently than younger individuals; 42% to 68% of older individuals may suffer from insomnia.1,5 From March 2004 to March 2005, approximately $2.3 billion was spent in the United States on prescription medications for insomnia, about $1.8 billion of which was spent on zolpidem, a benzodiazepine (BZD) receptor agonist.6 Other top sellers included zaleplon (a BZD receptor agonist) and triazolam (a BZD).6
CLASSIFICATION AND ETIOLOGY
Physicians should take a very thorough general medical history, collecting information about caffeine, drug, and alcohol use; medication use, including use of over-the-counter (OTC) or homeopathic agents; symptoms of depression or anxiety; and any pain symptoms. Physicians should then take a more specific sleep history, noting the onset, duration, frequency, and precipitator(s) of the sleep disturbance and, if applicable, any remedies that have helped and any history of insomnia that was previously resolved. Further evaluation may include having the patient maintain a sleep log, which may be helpful in determining whether there is an underlying disorder causing the patient's insomnia. Physical examination should be directed toward identifying underlying medical conditions.
Additional testing may be performed if the diagnosis still remains unclear despite a thorough history and physical examination and/or if routine treatment fails. Physicians may consider using polysomnography (PSG), a commonly performed diagnostic test, particularly if a breathing disorder is suspected (ie, if the patient or a bed partner reports snoring and/or interrupted breathing during sleep). PSG is typically performed in a sleep lab using multiple monitoring devices to assess various bodily functions including brain activity (electroencephalogram [EEG]), oxygen saturation (pulse oximetry), eye movements to evaluate stages of sleep (electrooculogram), and muscle movements (electromyelogram). Interpretation of these data will assist physicians in diagnosing the cause of a patient's insomnia, particularly if the underlying cause is obstructive sleep apnea.
Other specialized sleep tests are available but used less commonly. The multiple sleep latency test (observed naps with EEG monitoring) is used to assess daytime sleepiness as evidence of insomnia and to diagnose narcolepsy. This test is performed in a sleep lab, usually the morning after a PSG test. Another method for testing sleep patterns is actigraphy, in which patients wear a motion detector on the wrist; this method may be complementary to sleep log data, and information can be recorded over weeks during sleep periods at home. However, the usefulness of this modality is unclear.11 Neuroimaging studies also may be performed if a structural lesion is suspected.