What are the strengths and weaknesses of the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision (DSM‑5‑TR) and the International Classification of Diseases, Eleventh Revision (ICD‑11) in diagnosing hypersomnolence disorder?

Diagnostic Classification Systems for Hypersomnolence Disorder: DSM-5-TR vs ICD-11

DSM-5-TR Strengths

The DSM-5-TR provides superior clinical operationalization for hypersomnolence disorder through its requirement of 3-month symptom duration, at least 3 nights per week frequency, and mandatory functional impairment criteria, making it the preferred framework for psychiatric and sleep medicine practice. 1

Specific Diagnostic Criteria

• Requires quantifiable frequency threshold (≥3 nights/week for ≥3 months) that prevents overdiagnosis of transient sleep complaints 1
• Mandates clinically significant distress or functional impairment as a core diagnostic requirement, ensuring only pathological cases are diagnosed 1
• Explicitly excludes cases better explained by other sleep disorders, substance effects, or medical/mental conditions, reducing diagnostic confusion 1
• Distinguishes between sleep quantity complaints and true hypersomnolence by focusing on excessive sleep propensity and unintentional sleep episodes 1

Clinical Utility Features

• Integrates seamlessly with psychiatric differential diagnosis since mood disorders commonly present with hypersomnolence symptoms that lack objective sleepiness on MSLT 2
• Provides clear framework for ruling out secondary causes including medication effects, which are particularly common in older adults taking multiple sedating drugs 1, 3
• Emphasizes the distinction between subjective complaints ("tired," "fatigued") and true excessive sleepiness characterized by increased sleep propensity 1

DSM-5-TR Weaknesses

Lack of Objective Testing Integration

• Does not mandate polysomnography or MSLT despite these being essential for confirming central hypersomnolence and excluding sleep-disordered breathing 1, 3, 4
• Relies heavily on subjective reporting which is problematic since patients overestimate sleep time by ~1.5 hours and psychiatric patients rarely show objective sleepiness on MSLT despite severe subjective complaints 5, 2
• Fails to specify mean sleep latency thresholds (≤8 minutes on MSLT) that objectively define pathological sleepiness 3, 5

Insufficient Subtype Differentiation

• Does not distinguish between idiopathic hypersomnia with long sleep time (>10 hours) versus without long sleep time (6-10 hours), which represent clinically distinct phenotypes 1, 3
• Lacks criteria for identifying sleep inertia severity, a key distinguishing feature of idiopathic hypersomnia that significantly impacts functional impairment 4, 6
• Cannot differentiate hypersomnolence with psychiatric comorbidity from primary hypersomnia disorders, despite clustering analysis showing these represent distinct phenotypes with different treatment implications 6

Diagnostic Ambiguity

• Provides no guidance on medication washout requirements before diagnosis, despite stimulants, benzodiazepines, and antihistamines invalidating clinical assessment 1, 5
• Does not address the critical requirement to exclude obstructive sleep apnea first, which affects >50% of patients with excessive sleepiness 7

ICD-11 Strengths

Neurobiological Framework

• Aligns with International Classification of Sleep Disorders-3 (ICSD-3) which provides detailed neurobiological categorization of central hypersomnolence disorders 4, 8
• Facilitates research into pathophysiology by maintaining consistency with sleep medicine nomenclature used in clinical trials 1
• Better captures secondary hypersomnias due to specific medical conditions like Parkinson's disease, myotonic dystrophy, and Niemann-Pick disease type C 1, 3

International Standardization

• Provides universal coding system essential for epidemiological research and international treatment guideline development 4, 8
• Enables tracking of rare conditions like Kleine-Levin syndrome that require multinational data collection 1

ICD-11 Weaknesses

Clinical Implementation Barriers

• Lacks the operational specificity needed for routine clinical diagnosis including frequency thresholds and duration requirements that DSM-5-TR provides 1, 8
• Does not emphasize functional impairment criteria, potentially leading to overdiagnosis of clinically insignificant symptoms 1
• Provides insufficient guidance on excluding secondary causes systematically, particularly medication-induced hypersomnolence 1, 3

Diagnostic Test Limitations

• Does not address the poor reliability of MSLT which has suboptimal sensitivity and specificity, particularly when prior sleep is inadequate 5, 4, 8
• Fails to specify that 7-14 days of actigraphy-documented adequate sleep is mandatory before MSLT interpretation, the most common cause of false-positive results 5
• Does not weight diagnostic tests by specificity and sensitivity, leading to over-reliance on MSLT despite its limitations 8

Heterogeneity Problem

• Cannot capture the clinical heterogeneity within hypersomnolence disorder that clustering analyses reveal, including distinct phenotypes with and without psychiatric comorbidity 6
• Lacks hierarchical diagnostic structure with levels of certainty, making it difficult to apply when objective testing is equivocal 8

Critical Diagnostic Pitfalls Common to Both Systems

Medication Confounding

• Both systems inadequately address that sedating medications (benzodiazepines, opioids, antihistamines, certain antidepressants) are the most common overlooked cause of hypersomnolence in older adults 1, 3
• Neither specifies washout periods for stimulants, sedatives, and REM-suppressing medications before diagnostic testing 5

Psychiatric Overlap

• Depression commonly presents with hypersomnolence complaints but rarely shows objective sleepiness on MSLT, yet neither system provides clear differentiation criteria 2, 6
• Patients with psychiatric disorders and hypersomnolence often have elevated depressive symptoms, worse functional impairment, and longer sleep duration, representing a distinct phenotype that current classifications fail to capture 6

Testing Prerequisites

• Both fail to mandate that nocturnal sleep disorders (OSA, restless legs syndrome, periodic limb movements) must be excluded first with polysomnography before diagnosing primary hypersomnolence 1, 7
• Neither emphasizes that insufficient sleep syndrome due to lifestyle factors must be ruled out with objective actigraphy, not self-report 5, 7

Practical Clinical Algorithm

Step 1: Exclude Secondary Causes

• Perform comprehensive medication review focusing on benzodiazepines, opioids, antihistamines, antidepressants, and recent stimulant discontinuation 1, 3
• Order TSH, CBC, comprehensive metabolic panel including liver function to exclude hypothyroidism, anemia, and hepatic encephalopathy 3, 7
• Obtain brain MRI to identify structural causes including stroke, tumors, and neurodegenerative disease 3

Step 2: Objective Sleep Documentation

• Require 7-14 days of wrist actigraphy to objectively verify adequate sleep duration (≥6 hours for adults) and exclude insufficient sleep syndrome 5, 7
• Perform overnight polysomnography to exclude OSA, periodic limb movements, and other nocturnal disorders before proceeding 3, 5, 7

Step 3: Objective Sleepiness Testing

• Conduct MSLT only after confirming adequate prior sleep and negative PSG, with mean sleep latency ≤8 minutes indicating pathological sleepiness 3, 5
• Count sleep-onset REM periods (SOREMPs): ≥2 SOREMPs indicates narcolepsy; <2 SOREMPs with MSL ≤8 minutes indicates idiopathic hypersomnia 3, 5
• If CSF sampling is feasible and narcolepsy type 1 suspected, hypocretin-1 ≤110 pg/mL definitively confirms diagnosis and cannot be falsely positive from sleep deprivation 3, 5

Step 4: Phenotype Characterization

• Quantify total sleep time: >10 hours defines idiopathic hypersomnia with long sleep time; 6-10 hours defines the subtype without long sleep time 1, 3
• Assess sleep inertia severity using structured questionnaires, as severe sleep inertia distinguishes idiopathic hypersomnia from other causes 4, 6
• Screen for psychiatric comorbidity particularly depression, recognizing this may represent a distinct hypersomnolence phenotype requiring different treatment 2, 6