Introduction

Insomnia is a highly prevalent sleep disorder throughout the world.¹ It is defined as difficulty in initiating and maintaining sleep, or nonrestorative sleep associated with some type of daytime impairment or distress. It can occur as an independent disorder (ie, primary insomnia) or, more commonly, with 1 or more medical, psychiatric, or primary sleep disorders (comorbid insomnia). Insomnia is a chronic disorder and typically does not remit spontaneously. It is important to differentiate insomnia from sleep deprivation. Sleep deprivation refers to the loss of sleep associated with inadequate opportunity or circumstance for sleep. In contrast, insomnia refers to the loss of sleep despite adequate circumstance and opportunity to sleep but an inability to do so.²

The medical view of chronic insomnia and its impact in the medical, social, economic, and workplace spheres received renewed attention after an independent panel of sleep experts issued a State-of-the-Science Conference Statement on the condition in 2005, the first since 1983. The conference, sponsored by the National Institutes of Health, confirmed the significant prevalence of insomnia in conjunction with other medical and psychiatric conditions. More important, however, it gave credence to the fact that chronic insomnia is not simply a symptom of these other morbidities, but a separate medical disorder requiring treatment in its own right. A marker of this change is the acceptance of the term comorbid insomnia to replace the previously used secondary insomnia. The report also clearly identified the need to treat insomnia on a long-term basis.³

Prevalence estimates for insomnia vary widely. An estimated 4% to 40% of adults experience acute or transient forms of sleep disturbance in any 1-year period, while an estimated 10% of the American population meets diagnostic criteria for chronic insomnia, up to 50% of those receiving medical care.^3,4

At-risk populations include women, the elderly, shift workers, and individuals with comorbid physical and mental disorders.⁵ The condition is particularly prevalent in individuals with psychiatric conditions, including major depressive disorder and anxiety disorders.^6,7

The comorbidities associated with insomnia are many, including altered mood; impaired functionality; increased risk for depression; increased sensitivity to pain; increased risk of falls in the elderly; attention, concentration, or memory impairment; reduction in motivation and energy; increased risk of errors at work and accidents while driving; headaches and gastrointestinal symptoms; and fatigue/malaise.⁸

This supplement reviews the current evidence regarding comorbid insomnia in various populations. The first article, by Thomas Roth, PhD, describes the incidence and impact of comorbid insomnia from an economic, medical, and treatment perspective. Most importantly, it conveys the emerging body of evidence pointing to the need to treat insomnia and any existing comorbidities as separate conditions, a new paradigm in the treatment of insomnia.

In the second article, Christina S. McCrae, PhD, addresses comorbid insomnia in the elderly, particularly as it relates to pain. She underscores the fact that although changes in sleep architecture occur with age, they are not the primary source of the increased prevalence of insomnia in older individuals. Rather, clinicians need to be aware of the extraordinarily high prevalence of comorbid insomnia in this population, and view an insomnia complaint as a potential marker for other medical or psychiatric conditions. She also details the existing literature on treating comorbid insomnia in this population.

In the final article, David N. Neubauer, MD, addresses pharmacologic and nonpharmacologic treatment options for comorbid insomnia, including emerging new therapies and treatment paradigms. He describes 3 medications that have been specifically studied in comorbid insomnia, as well as several studies examining the use of behavioral therapies to address comorbid insomnia.

These articles provide an opening for a continuing discussion about the need to revisit current assumptions regarding insomnia as an important factor in the overall status of patients with medical and psychiatric conditions. In addition, they appreciate the impact that treating the insomnia as well as the comorbid condition may have on both conditions, and on the patient’s overall health.

1. Sateia MJ, Doghramji K, Hauri PJ, Morin CM. Evaluation of chronic insomnia. An American Academy of Sleep Medicine review. Sleep. 2000;23(2):243-308.

2. American Psychiatric Association. Diagnostic criteria for primary insomnia. Diagnostic and Statistical Manual ofMental Disorders. 4th ed. Washington, DC: American Psychiatric Association; 1994.

3. NIH State-of-the-Science Conference Statement on manifestations and management of chronic insomnia in adults. NIH Consens State Sci Statements. 2005;22(2):1-30.

4. Hohagen F, Rink K, Kappler C, et al. Prevalence and treatment of insomnia in general practice. A longitudinal study. Eur Arch Psychiatry Clin Neurosci. 1993;242(6):329-336.

5. Roth T. Prevalence, associated risks, and treatment patterns of insomnia. J Clin Psychiatry. 2005;66(suppl 9):10-13.

6. Ford DE, Kamerow DB. Epidemiologic study of sleep disturbances and psychiatric disorders. An opportunity for prevention? JAMA. 1989;262(11):1479-1484.

7. Katz DA, McHorney CA. Clinical correlates of insomnia in patients with chronic illness. Arch Intern Med. 1998;158(10):1099-1107.

8. Neubauer DN. Insomnia. Prim Care. 2005;32(2):375-388.

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