Clinical Review of Insomnia: Diagnosis and Treatment

Insomnia: Diagnosis and Treatment
Introduction and Prevalence

  • Insomnia is a pervasive health issue, affecting over 50 million Americans who report sleep-related problems.

  • The 2005 Sleep in America Poll indicated:

    • 75\% of individuals reported one or more sleep problems, including difficulty falling asleep, frequent or early morning awakenings, daytime drowsiness, snoring, or sleep apnea.

    • More than 50\% experienced at least one insomnia symptom in the past year, with one-third reporting symptoms nearly every night.

    • Most common symptoms: daytime drowsiness (38\%$) and frequent awakenings (32\%$).

  • Insomnia is more prevalent in women (especially postmenopausal) and the elderly.

  • Predisposing factors include snoring and comorbid psychiatric or medical illnesses.

  • Despite its recognition, insomnia remains under-recognized and often inadequately treated; less than half of those surveyed in the 2005 poll discussed their sleep problems with a physician.

  • Direct-to-consumer advertising has increased awareness of pharmacologic treatments but may have diminished awareness of behavioral therapies.

Definition and Classification of Insomnia

  • Definition: Subjective complaint of poor sleep quality or quantity despite adequate time for sleep, resulting in daytime fatigue, irritability, and decreased concentration.

  • Specific Sleep Complaints: Delayed sleep onset, frequent awakenings, early morning awakenings, and waking up feeling unrefreshed.

  • Primary (Idiopathic) vs. Comorbid (Secondary) Insomnia:

    • Comorbid Insomnia: Associated with:

      • Psychiatric disorders: e.g., dementia, depression, anxiety disorders.

      • Medical disorders: e.g., gastroesophageal reflux disease, chronic pain, asthma.

      • Substance abuse: e.g., alcoholism, abuse of prescription or nonprescription medications, illicit drug use.

      • Specific sleep disorders: e.g., periodic limb movement disorder, restless legs syndrome, circadian rhythm sleep disorders, sleep apnea.

    • Primary Insomnia: Diagnosed by exclusion when other causes are ruled out. Associated with chronic stress, poor sleep hygiene, learned insomnia, and sleep-state misperception where patients complain of insomnia without objective evidence.

  • Acute vs. Chronic Insomnia (based on duration):

    • Acute Insomnia: Sleep problems lasting from one night to a few weeks. Often caused by emotional or physical stressors like illness, jet lag, or environmental disturbances.

    • Chronic Insomnia: Sleep problems lasting at least three nights weekly for at least one month. Most often associated with comorbid medical or psychological disorders.

  • Additional Classification Schemes:

    • DSM-IV-TR: Categorizes sleep disorders into primary sleep disorders, sleep disorders related to another mental disorder, sleep disorders due to a medical disorder, and substance-induced sleep disorders.

    • International Classification of Sleep Disorders, Revised (ICSD): Classifies sleep disorders into dyssomnias, parasomnias, sleep disorders associated with comorbid diseases, and proposed sleep disorders. Insomnia is classified as a dyssomnia, further characterized as intrinsic, extrinsic, or a circadian rhythm sleep disorder.

Sleep Basics

  • Functions of Sleep: Plays a vital role in health, though specific functions are not fully agreed upon. Potential roles include restorative functions and energy conservation. Sleep needs depend on age and activity.

  • Sleep Stages: Divided into two general states:

    • Nonrapid Eye Movement (NREM) Sleep: Comprises four stages:

      • Stage 1: Transition period between wakefulness and early sleep.

      • Stage 2 (Intermediate Sleep): Represents the largest percentage of total sleep time.

      • Stages 3 and 4 (Deep Sleep): Considered the restorative sleep stages.

    • Rapid Eye Movement (REM) Sleep: Follows NREM sleep. Characterized by physiological changes (variations in blood pressure, heart rate, respiratory rate) and quick, irregular eye movements. Dreaming occurs in REM sleep. May be vital for memory consolidation and potentially sustaining life.

  • Normal Sleep Cycle: A complete cycle lasts approximately 1.5-2 hours and is repeated four to five times per night. The amount of time in each stage changes, with Stage 2 and REM sleep typically increasing with sequential cycles.

  • Alterations in Sleep Architecture: Can be caused by medications, sleep disorders (e.g., narcolepsy), and age (time in Stages 3 and 4 decreases, Stage 1 increases with age).

  • Objective Sleep Assessment Tools:

    • Multiple Sleep Latency Test (MSLT): Objectively assesses daytime sleepiness by measuring the time it takes to fall asleep. Not for routine insomnia diagnosis.

    • Polysomnography: Typically an overnight sleep study; continuously records electroencephalogram (EEG), REMs, and muscle tone.

    • Wrist Actigraphy: Adjuctively used to record wrist movement and determine sleep time.

Diagnosis

  • Multifactorial Approach: Requires a thorough medical history and physical examination, focusing on the patient’s sleep history.

  • Comprehensive Sleep History: Should cover sleep habits, drug (prescription and nonprescription), alcohol, nicotine, and caffeine consumption, comorbid illnesses, and sleep environment.

  • Physical Examination: Helps identify medical conditions contributing to insomnia.

  • Additional Information Sources: Interviewing bed partners or caregivers.

  • Sleep Diary: A 1- to 2-week diary allows patients to record bedtime, total sleep time, time to sleep onset, number of awakenings, medication use, morning awakening time, and subjective morning feeling.

  • Direct Questioning: Often necessary as many patients do not voluntarily discuss sleep problems with their primary care providers.

  • Sleep Studies: Polysomnography and MSLT may be required if the patient’s history and presentation support their use.

  • Treatment Identification: Effective treatments are identified only after careful review of sleep history and studies.

Consequences of Insomnia

  • Acute Insomnia: Sleepiness, mood changes, and impairment of daytime functioning.

  • General Consequences: Interference with interpersonal relationships and job performance, increased healthcare utilization.

  • Chronic Insomnia: Linked to increased absenteeism from work, increased risk of psychiatric disorders, impaired cognition, and a negative impact on quality of life.

  • These significant effects underscore the necessity of appropriate treatment.

Nonpharmacologic Therapies

  • Often referred to collectively as Cognitive Behavioral Therapy (CBT).

  • Other Evaluated Modalities: Yoga, light therapy, and acupuncture, though not adequately studied.

  • Components of CBT:

    • Sleep-Hygiene Education: Focuses on environmental factors and attitudes that negatively affect sleep.

      • Recommendations: Maintain a regular sleep schedule, exercise regularly (avoid close to bedtime), avoid stimulants (caffeine, nicotine) before bedtime, ensure a comfortable sleep environment (eliminate noise, decrease light, comfortable temperature), and avoid negative thinking or clock-watching.

      • Note: Ineffective when used alone.

    • Stimulus-Control Therapy: Aims to eliminate maladaptive behaviors and associate the bedroom with sleep.

      • Instructions: Go to bed only when tired, use the bedroom only for sleeping, establish a normal sleep-wake schedule, avoid napping. If unable to fall asleep within 15 minutes, leave the bedroom and return only when tired.

    • Relaxation Therapy: Includes progressive muscle relaxation, biofeedback, and meditation. Particularly helpful for patients with suspected hyperarousal. May improve both sleep latency and sleep maintenance.

    • Sleep-Restriction Therapy: Improves sleep efficiency by temporarily inducing sleep deprivation.

  • Effectiveness of Nonpharmacologic Interventions:

    • Numerous studies and meta-analyses demonstrate effectiveness, with 50\%

    • -80\% of patients responding.

    • Improved sleep patterns and subjective reports of sleep.

    • Most effective interventions: stimulus control and sleep restriction.

    • Improvements can be maintained for six months or more after therapy completion, including decreased sleep latency and improved sleep maintenance.

Pharmacologic Therapies

  • Benzodiazepines:

    • Mechanism of Action: Bind to \gamma-aminobutyric acid-A (GABA-A) receptors on postsynaptic neurons in the central nervous system, increasing neuronal chloride permeability and inhibiting neuronal excitation.

    • Agents Labeled for Insomnia: Estazolam, flurazepam, quazepam, temazepam, and triazolam (vary in onset and duration).

      • Estazolam: Oral dose 1-2mg, Onset 60min, Half-life 10-24hr.

      • Flurazepam hydrochloride: Oral dose 15-30mg, Onset 15-30min, Half-life 47-100hr (includes active metabolites).

      • Quazepam: Oral dose 7.5-15mg, Onset 20-45min, Half-life 25-84hr (includes active metabolites).

      • Temazepam: Oral dose 7.5-30mg, Onset 30-60min, Half-life 4-18hr.

      • Triazolam: Oral dose 0.125-0.25mg, Onset 15-30min, Half-life 2-4hr.

    • Efficacy: A 2000 meta-analysis showed benzodiazepines increased total sleep time but had no significant effect on sleep latency. No controlled studies demonstrate efficacy beyond 12 weeks.

    • Adverse Effects: Daytime sleepiness/hangover effect, dizziness, impaired memory. Agents with short half-lives are associated with anterograde amnesia. Longer half-life agents increase the risk of hangover, confusion, dizziness, and falls.

    • Sleep Architecture: Cause changes including increased Stage 2 sleep and increased REM latency.

    • Abuse Potential and Dependence: Schedule IV medications with potential for abuse. Physical dependence can develop in a few days. Abrupt discontinuation can lead to withdrawal symptoms (anxiety, rebound insomnia, tachycardia, diarrhea).

    • Special Populations: Dosage reductions are important in the elderly to decrease fall risk.

    • Tolerance: May occur more rapidly with short half-life agents (triazolam, temazepam), increasing rebound insomnia risk.

    • Drug Interactions: Estazolam and triazolam should be avoided with cytochrome P-450 (CYP) isoenzyme 3A4 inhibitors (decreased clearance). Interact with alcohol and other CNS depressants.

  • Benzodiazepine-Receptor Agonists (Z-drugs):

    • Mechanism of Action: Exert effects on the \omega-receptor of the GABA-A receptor complex, inhibiting neuronal excitation through increased chloride permeability.

    • Agents: Zolpidem, zaleplon, and eszopiclone. All are Schedule IV drugs.

      • Zolpidem tartrate: Oral dose 5-10mg, Onset 30min, Half-life 1.4-4.5hr.

      • Zolpidem tartrate, extended release: Oral dose 6.25-12.5mg, Onset 30min, Half-life 1.6-5.5hr. (Not restricted to short-term use).

      • Zaleplon: Oral dose 10-20mg, Onset 20min, Half-life 0.5-1hr. (Not useful for sleep-maintenance insomnia).

      • Eszopiclone: Oral dose 2-3mg, Onset 30min, Half-life 6hr. (Not restricted to short-term use).

    • Purported Benefits (vs. Benzodiazepines): Less rebound insomnia, less abuse potential, fewer dependency problems, and less hangover effect. However, reports highlight real abuse and dependency potential.

    • Sleep Architecture: Zolpidem has not been shown to have deleterious effects on the normal sleep cycle.

    • Adverse Effects: Zolpidem has been associated with parasomnias (sleepwalking, sleep-related eating disorders). Eszopiclone's most common adverse effect is an unpleasant taste.

    • Administration: Intermittent zolpidem administration is as effective as nightly use. Zaleplon's short duration allows for middle-of-the-night dosing if at least four hours remain before planned awakening. Administration with food should be avoided as it may delay onset and diminish effectiveness.

    • Dosage Adjustment: Eszopiclone dosage can be adjusted (1-2mg for sleep latency, 3mg for sleep maintenance).

    • Cost: Generally more costly than generic benzodiazepines.

  • Melatonin-Receptor Agonists:

    • Agent: Ramelteon (first and only in this new class).

    • Mechanism of Action: Selectively targets MT1 and MT2 melatonin receptors in the hypothalamus, involved in the sleep-wake cycle. Does not have affinity for GABA receptors.

    • Controlled Substance Status: The only sedative hypnotic not classified as a controlled substance.

    • Dosage: Recommended 8mg within 30 minutes of bedtime. No dosage reduction needed in the elderly.

    • Metabolism: Metabolized by CYP1A2, posing potential for drug interactions.

    • Efficacy: Labeled for delayed sleep onset. Recent studies show it also significantly shortens sleep onset delay and increases total sleep time.

    • Adverse Effects: Most common are somnolence, fatigue, and dizziness. No evidence of rebound insomnia.

    • Duration of Use: Not limited to short-term use.

    • Administration: Should not be taken with or immediately after a high-fat meal to avoid delayed absorption and reduced effects.

    • Contraindications: Generally avoided in patients with severe hepatic impairment.

  • Antidepressants, Antipsychotics, and Barbiturates:

    • Antidepressants: Often prescribed for primary insomnia, despite limited evidence for efficacy or safety for this indication alone. Possible reasons for use include physician perception of safety compared to hypnotics and fewer prescribing restrictions.

      • Examples: Trazodone, tricyclic antidepressants (TCAs like doxepin, amitriptyline), mirtazapine.

      • Trazodone: Most frequently used (50-100mg). One study showed it improved sleep latency and maintenance compared to placebo, but zolpidem was superior. Adverse effects include dizziness, sedation, hypotension, headache, and priapism.

      • TCAs: Adverse effects include anticholinergic effects (sedation, constipation, dry mouth), weight gain, cardiac arrhythmias, lowered seizure threshold, and extrapyramidal symptoms.

      • Optimal Use: More beneficial for patients with comorbid depression or as alternative agents for chronic treatment.

  • Nonprescription Agents:

    • Antihistamines (First-generation): e.g., diphenhydramine, doxylamine. Common ingredients in OTC sleep aids, but usage is not strongly supported by data. Patients quickly develop tolerance to sedative effects, and they haven't been shown to improve sleep effectively. Adverse effects: hangover effect, dizziness, dry mouth, constipation. Recommendations are limited to infrequent insomnia symptoms, and caution is advised for patients with comorbid conditions like glaucoma or increased fall risk (especially the elderly).

    • Melatonin: A hormone. Data supporting its use for insomnia are minimal. The minimum effective dosage is unknown, and lack of ingredient standardization in the U.S. means it is not recommended for routine treatment.

    • Valerian: Mechanism of action not fully understood but purported to interact with GABA receptors. Little evidence supports its use. Appears on FDA’s Generally Recognized as Safe (GRAS) list. Potential adverse effects include dizziness, nausea, headache, and upset stomach. Lack of stringent FDA regulation for supplements means unstandardized ingredients and increased patient harm risk.

Choice of Agent

  • Selection should be based on patient-specific factors:

    • Age

    • Proposed length of treatment

    • Primary sleep complaint (e.g., sleep onset vs. maintenance)

    • History of drug or alcohol abuse

    • Cost

  • Elderly: Dosage reduction of benzodiazepines and benzodiazepine-receptor agonists is prudent to minimize fall risk.

  • Sleep Latency Problems: Agents with quick onset and shorter half-lives (e.g., temazepam, zaleplon) are ideal.

  • Sleep Maintenance Problems: Agents with longer half-lives (e.g., quazepam, zolpidem, eszopiclone) are more suitable.

  • History of Substance Abuse: Benzodiazepines should generally be avoided. Ramelteon is an option as it is not a controlled substance and is approved for long-term use.

  • Comorbid Depression: Antidepressants are a reasonable option and can be offered as an alternative for long-term treatment.

  • Cost: Benzodiazepines and antidepressants may be less costly than benzodiazepine-receptor agonists and ramelteon.

  • Nonprescription Agents: Should be reserved for patients with infrequent symptoms and no limiting comorbid medical conditions due to limited efficacy and potential side effects.

Combining Nonpharmacologic and Pharmacologic Therapies

  • Direct comparative studies are limited.

  • One small randomized controlled trial (n=\63) found:

    • CBT alone or in combination with drug therapy was more effective at improving delays in sleep onset than drug therapy alone or placebo.

    • CBT (including sleep-restriction, stimulus-control, and relaxation techniques) was more efficacious at sustaining benefits after discontinuation than pharmacologic therapy.

    • Combination therapy provided no additional advantage over CBT alone for sustaining improvements in sleep onset.

  • Implication: These data support nonpharmacologic interventions as first-line therapy, though the study's small sample limits generalizability to sleep-maintenance problems or patients with comorbid conditions.

  • Conclusion: Nonpharmacologic therapies, offering benefits with minimal adverse effects, should remain a first-line option. Further research is needed to refine specific behavioral techniques, optimal therapy length, and delivery methods.

Barriers to Diagnosis and Treatment

  • Physician-Related Barriers:

    • Limited physician awareness or training in diagnosing and treating sleep disorders, leading to underdiagnosis, misdiagnosis, and delayed diagnosis, which increases morbidity and healthcare utilization.

    • Perception that current treatments are ineffective or risky (e.g., concerns about dependence/abuse with pharmacologic agents).

    • Clinicians may fail to recognize the effectiveness of behavioral therapies.

  • Patient-Related Barriers:

    • Lack of discussion during patient consultations, often because patients or physicians do not view insomnia as an important medical problem, or consultation time is perceived as too short.

    • Patients may fail to recognize their sleep-related symptoms as problems (e.g., only 21\% of survey respondents with symptoms believed they had a sleep problem, and only 29\% reported being asked about sleep by a physician).

  • Research/Outcomes Data Limitations:

    • Many treatment studies do not assess long-term outcomes such as improved quality of life, job performance, or interpersonal relationships due to a lack of standardized documentation and effective assessment instruments.

    • Current outcome evaluation often relies on nonvalidated assessment tools lacking sensitivity and precision.

    • Pharmacologic treatments have traditionally been recommended for only 7-10 days, despite patients often having symptoms beyond this period; longer-term use studies are only recent.

Investigational Agents and Future Research

  • Investigational Agents:

    • Indiplon: A nonbenzodiazepine hypnotic that binds directly to the GABA-A receptor, preferentially to the \alpha-subunit. Purportedly the most potent GABA-A agonist, being 10 times more potent than zolpidem and 50 times more potent than zaleplon. All dosage forms are currently unavailable.

    • Eplivanserin: Currently in Phase III trials for sleep-maintenance insomnia in adults. It is a serotonin type 2A-receptor antagonist.

  • Future Research Needs:

    • Direct comparisons of benzodiazepines versus newer hypnotic agents (Z-drugs, ramelteon) to determine the most cost-effective treatment.

    • Comparison of hypnotic agents with nonpharmacologic therapies and combination therapy.

    • Increased focus on long-term outcomes of therapy, including improved quality of life, job performance, and interpersonal relationships, beyond just reductions in sleep latency or improvements in sleep maintenance.