Karl Doghramji, MD, FAASM, DFAPA
Insomnia is the complaint of dissatisfaction with sleep quantity or quality associated with an inability to fall or stay asleep or early-morning awakening.1 Considerable changes have occurred in our understanding of insomnia over the past few decades.2 Whereas it was once thought to be an uncommon malady, we now know that it is highly prevalent in clinical settings; after pain, it represents the second-most commonly expressed clinical complaint.3 In community settings, an astounding 35% of the adult population experiences insomnia during the course of 1 year, and that half experiences the problem as severe. Literature suggests 20.1% of adults are dissatisfied with their sleep or take medication for sleeping difficulties.4,5 Insomnia is also an emerging problem in children and adolescents; an estimated 4% of children complain of insomnia at least 3 times per week over the course of a year.6,7
Although it was once regarded as a benign condition, insomnia is now also known to be associated with a variety of health risks and consequences. Insomniacs suffer from greater functional impairments, cognitive deficits, work-related impairments and absenteeism, social upheaval, and mood impairments than do good sleepers.8,9 They also exhibit greater cognitive deficits, especially when responding to challenging reaction time tasks.10-13 Insomnia also contributes to the development of new cardiovascular and metabolic abnormalities such as hypertension, heart failure, and glucose intolerance.14-18
Difficulty falling asleep, frequent nocturnal awakenings, early- morning awakening, nonrestorative sleep, decreased total sleep, and disturbing dreams are commonly reported by patients with major depression.4,19,20 However, persistent insomnia, even in the absence of current mood or other disorders, confers an increased future risk of the development of depression and other new psychiatric disorders over the course of the ensuing year, a risk that diminishes if the insomnia resolves and after direct management of insomnia.20-27 Insomnia also contributes to suicidal ideation and behavior, and direct management of insomnia diminishes suicidal ideation.28 There may, therefore, exist a bidirectional relationship between insomnia and various psychiatric disorders including depression.
Earlier formulations into the pathophysiology of insomnia were based on the notion that insomnia represented a failure of the normal process of dreaming, leading to anxiety resulting in awakenings.29
Later formulations focused on cognitive and behavioral principles; insomniacs were theorized to have an exaggerated emotional reaction to everyday stressors, compounded by distorted and negative beliefs about sleep that led to a cycle of catastrophizing apprehension and worry.30 More recent research has implicated the role of an overly active physiological arousal system, both during sleep and wakefulness. Insomniacs are so aroused that they have a decreased ability to fall asleep during daytime nap tests,31 display increased high-frequency beta electroencephalogram power across the entire night,32 and have an increase in positron emission tomography global glucose metabolic rates during both wakefulness and sleep compared with healthy controls.33 Insomniacs also exhibit an increase in heart rate and an increase in whole-body metabolic rate.34-36
The current view of insomnia, which supports the possibility of its existence as an autonomous disorder, is reflected in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition.37
The primary insomnia diagnosis that appeared in prior versions is eliminated, in favor of insomnia disorder, and secondary insomnia conditions are eliminated altogether, in favor of insomnia disorder with concurrent specification of clinically comorbid medical and psychiatric conditions.
We now recognize that the complex nature of insomnia necessitates a systematic evaluation prior to proceeding with treatment, as noted in a number of recently published guidelines.7,38,39 The Insomnia Severity Index is a useful clinical tool for identifying insomnia and measuring severity.40 Digital sleep diaries now afford patients the opportunity to display sleep-wake patterns over time and assist in clinical diagnosis. An actigraph, through a device resembling a wristwatch, records movement and ambient light levels and can be useful for the assessment of sleep patterns and the response to behavioral or pharmacological treatments.41
Cognitive-behavioral therapy for insomnia (CBT-I) remains the gold standard for insomnia treatment, with proven techniques such as sleep hygiene education, stimulus control therapy, relaxation therapies, restriction of time in bed, cognitive therapy, and paradoxical intention.42,43 Limitations in availability of CBT-I are now being addressed by the introduction of unguided online and smartphone CBT-I modules and techniques that can be delivered over 4 weeks. Significant advances have also been made in the pharmacological management of insomnia, which had, over the past few decades, relied on older benzodiazepine receptor agonists. More recently, a melatonin receptor agonist, a histamine-1 receptor antagonist, and 2 orexin receptor antagonists have been introduced, and more are being developed. With the increase in the array of available hypnotics, each with identifiable clinical effects, clinicians can now select hypnotic agents based on specific clinical and disease characteristics, such as age, specific insomnia type (initiation vs maintenance insomnia), presence of respiratory comorbidities (chronic obstructive pulmonary disease, sleep apnea), and a history of substance use/abuse.44
In conclusion, decades of research confirms that insomnia is a highly prevalent condition with a variety of health risks and clinical consequences. Neurophysiological studies indicate that it is likely a disturbance of central nervous system hyperarousal with far-reaching effects throughout the body. In addition, it is now viewed as an autonomous disorder that is capable of interacting with comorbid disorders in a bidirectional fashion. A plethora of cognitive/behavioral and pharmacological treatments are also available to the clinician to address the specific clinical needs of the patient with insomnia.
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