Correlates and consequences of chronic insomnia
Introduction
The Diagnostic and Statistical Manual of Mental Disorders, fourth edition (DSM-IV), defines primary insomnia as difficulty initiating sleep or maintaining sleep, or sleep that is nonrestorative; furthermore, these difficulties must result in impaired functioning or significant feelings of distress. The DSM-IV also recognizes several forms of “secondary insomnia,” including “insomnia related to another mental disorder”; “sleep disorder due to a general medical condition, insomnia type”; or “substance-induced sleep disorder, insomnia type” [1]. In general, hospital practice, insomnia secondary to psychiatric [2], [3], [4], [5], [6], [7], [8], [9], [10], [11] or medical disorders, or aging [3], [12], [13], [14], [15], [16], [17] is a common presentation. Frequently, chronic insomnia, defined as insomnia persisting longer than 3 weeks [18], is a consequence of other conditions such as depression, anxiety, pain or advanced age, rather than a primary condition [3], [11], [13], [16], [17]. Indeed, psychiatric disorders account for at least 40% of the underlying diagnoses in patients with chronic insomnia [19], [20]. Physicians are often faced with a complex differential diagnosis, as a patient's psychiatric illness (such as depression) may coexist with one or more of the many underlying chronic medical disorders that also cause insomnia [18], [21], [22], [23]. Chronic medical conditions associated with depression include chronic pain syndromes [24], [25], [26], coronary heart disease [27], [28], sleep-disordered breathing [29], Parkinson's disease [30], asthma, gastrointestinal disorders, vascular disorders, chronic fatigue syndrome, and endocrine and metabolic disorders [21]. Insomnia is associated with various adverse sequelae in psychiatric, neurocognitive and medical domains [3], [8], [16], [31] as well as significant reduction in quality of life [31].
However, despite such detriments, many cases of insomnia go undiagnosed and untreated [3], [12], [32], [33]. For example, a survey conducted by the National Sleep Foundation [34] found that only 46% of patients with chronic insomnia had ever consulted their physician about sleep problems [32]. Although chronic insomnia was found to be associated with a number of deleterious effects in this survey, as many as 25% of patients with chronic insomnia felt that their sleep problem was too trivial to discuss. Another survey showed that primary care physicians seldom take sleep histories [35]. Taken together, these studies suggest the need for physicians to take a sleep history and to emphasize the role of good sleep in general health and well-being. In addition, although the vast majority of patients with insomnia experience difficulty maintaining rather than initiating sleep [13], [31], [32], [36], [37], [38], [39], [40], [41], clinicians may not recognize the importance of improving sleep maintenance (or keeping the patient asleep throughout the night) as a major treatment goal.
It is clear then that physicians must have a sophisticated understanding of insomnia in order to design an optimal care plan for the patient. This paper provides an overview of the prevalence, nature, impact and treatment of insomnia associated with psychiatric conditions.
Section snippets
Classification of chronic insomnia
Insomnia may be viewed both as a primary disorder and as a symptom of a medical, psychiatric, circadian or other sleep disorder by DSM-IV-TR criteria (discussed in the Introduction). Similar to other CNS disorders (i.e., headache), such a classification system provides the clinician with a tool to assist in differential diagnosis and, most importantly, in deciding the type and course of therapy necessary for effectively treating the specific problem. The optimal therapy for restless legs
Prevalence
Approximately 10% to 15% of adults suffer from chronic insomnia, and an additional 25% to 35% have transient or occasional difficulties sleeping [12]. Results of clinical practice surveys indicate that about two thirds of cases of insomnia are associated with a primary psychiatric or medical disorder [47], although one large epidemiological study [43] reported slightly lower prevalence rates of secondary insomnia (40%). Another community-based sample of 1536 subjects in Upper Bavaria found that
Etiology of chronic insomnia
Insomnia is a nonspecific condition characteristic of a number of medical and mental disorders. Its etiology may be related to the primary illness or its treatments. Insomnia is a common feature of several psychiatric disorders, most notably depression and anxiety (see Table 1) [1], [49], [50], [51], [52], [53], but, unfortunately, the medications used to treat these conditions, including the most commonly prescribed antidepressants [the selective serotonin reuptake inhibitors (SSRIs),
Sleep symptoms
Results of a meta-analysis of 177 studies of sleep patterns characteristic of psychiatric disorders documented the ubiquity of insomnia among patients with mood disorders, alcoholism, anxiety disorders, borderline personality disorder, schizophrenia and dementia [56]. Sleep continuity disturbances were the most prevalent, and when polysomnographic studies were obtained, decreased total sleep time, reduced sleep efficiency (defined as percentage of total recorded time in bed spent asleep) and
Impact of insomnia
Although the personal burden and direct and indirect costs related to insomnia in general are high (see Table 5) [7], [8], [43], [72], [73], [74], little research has evaluated the costs or personal burden related directly to secondary insomnia.
In the United States, total direct costs attributable to insomnia (outpatient visits to healthcare professionals, inpatient or nursing home care, prescription and nonprescription medications for insomnia) are estimated at approximately US$12 billion for
Insomnia or psychiatric disorders: which comes first?
The historical assumption is that psychiatric disorders cause insomnia [1], [16], [95]. However, epidemiologic data suggest that insomnia can antedate the development of major depression [43], [44], [74]. In a longitudinal study involving 7954 US adults, Ford and Kamerow [43] found that persons with persistent insomnia at the outset of the study were at a 40-fold higher risk of developing a new major depressive illness within a 1-year period, compared with persons without insomnia at the 1-year
Assessment of insomnia
A variety of diagnostic tools are used to identify and characterize insomnia. In the primary care setting, time restraints preclude extensive evaluation, and, so, several core diagnostic tools are used:
Sleep history
Medical history (including pain assessment and evaluation of medications)
Psychiatric history (augmented by a mental status examination)
Physical examination (especially body habitus and examination of eyes, ear, nose, throat, neck and blood pressure)
Laboratory testing as required
The
Treatment of insomnia
Limited data are available to give guidance in the treatment of insomnia in patients with a primary psychiatric condition and secondary insomnia. The prevailing clinical wisdom is that treatment of the underlying psychiatric condition (and coexisting contributing medical condition) will result in amelioration of accompanying insomnia [3], [33]. However, in light of the aforementioned adverse psychosocial, economic and clinical consequences of chronic insomnia, effective measures should be
Treatment options
Both pharmacological and behavioral therapies are used to treat secondary insomnia. As most patients with secondary insomnia suffer from sleep maintenance problems, treatment of secondary insomnia should focus on improving sleep continuity (sleep maintenance) and quality of sleep, as well as decreasing sleep latency and increasing total sleep time. Ideally, treatment should not impair next-day function. Nonpharmacologic treatments include cognitive behavioral therapies such as sleep hygiene
Summary and conclusions
Chronic insomnia is a highly prevalent problem that has not been given due attention in clinical practice. Epidemiologic data indicate that psychiatric disorders account for approximately one half of the cases of secondary insomnia, with depressive and anxiety disorders being the most commonly implicated. While treatment of the primary disorder is critical, treating the secondary insomnia should not be overlooked because lack of treatment may result in serious psychosocial, economic and
Acknowledgments
The author would like to acknowledge the editorial and technical support of Amy Yamamoto, as well as the assistance of Sepracor, Inc., in the preparation of this paper.
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