Abstract
Background
Sleep is a key biomarker of physical and mental health, with insufficient sleep duration and fragmentation associated with increased risks of hypertension and cardiometabolic disorders, reduced cognitive performance, and impaired emotional well-being.[1] Across clinical populations, sleep disturbance is particularly prevalent in chronic pain, with estimates ranging from 67% to 88%.[2]
Methods
This review synthesizes clinically substantive evidence spanning the principal ICSD-aligned sleep-disorder groupings represented in the provided sources: insomnia disorder, sleep-related breathing disorders (with emphasis on OSA/OSAS), central disorders of hypersomnolence (with emphasis on narcolepsy), circadian rhythm sleep-wake disorders (with emphasis on DSWPD/DSPS and SWSD), parasomnias (with emphasis on RBD), and sleep-related movement disorders (with emphasis on RLS/PLMS).[3–8] Diagnostic tools and therapeutics are summarized with attention to objective thresholds (e.g., MSLT criteria, AHI scoring rules, clinically meaningful change thresholds) and to emerging implementation and biomarker issues (e.g., HSAT/wearables and validation limitations).[1, 9–12]
Key findings
Insomnia disorder is the most prevalent sleep disorder, with short-term insomnia affecting approximately 30% to 50% of adults and up to 10% meeting criteria for chronic insomnia, which requires symptoms at least three times per week for at least three months.[3, 13] OSA is common and consequential, with an estimated global burden affecting hundreds of millions to one billion people and associations with daytime sleepiness and increased cardiovascular morbidity and mortality; untreated OSAS is linked to a two- to threefold higher risk of stroke and all-cause mortality.[4, 12] Narcolepsy is rare but disabling, typically with onset in adolescence or early adulthood and a diagnostic delay of 8–12 years; diagnostic confirmation relies on PSG followed by MSLT, with NT1 characterized by cataplexy and CSF hypocretin-1 <110 pg/mL.[5, 9, 14, 15] DSWPD affects an estimated 7% to 16% of adolescents and young adults and is distinguished by delayed circadian phase, for which delayed DLMO is highly sensitive and specific.[16, 17] RBD is a REM-related parasomnia with general-population prevalence of approximately 0.5% to 1% and strong prognostic significance: longitudinal cohorts indicate 80% to 90% develop an overt synucleinopathy within 10–15 years and meta-analytic conversion rates reach 97% by 14 years in some datasets.[18, 19] For RLS, prevalence varies by method and region but population studies report roughly 10% with symptoms and approximately 2% to 3% with clinically significant disease; pathophysiology centers on brain iron deficiency and dopaminergic dysfunction, and recent guidance emphasizes iron repletion and α2δ ligands while deprioritizing dopamine agonists because of augmentation risk.[8, 20, 21]
Conclusions
Across categories, contemporary practice increasingly hinges on phenotype-aware diagnostics (e.g., endotype-informed OSA models; biomarker-anchored circadian phase measures; CSF hypocretin-1 for NT1; iron indices and emerging CSF iron markers in RLS) and on mechanism-directed therapeutics (e.g., DORAs in insomnia; incretin-based weight-loss therapy for obesity-associated OSA; orexin-2 receptor agonism in narcolepsy development pipelines).[9, 10, 12, 15, 17, 22, 23]
1. Introduction and classification framework
Sleep disorders are clinically heterogeneous yet share a common public-health signature: insufficient sleep duration and fragmentation are associated with increased risk of hypertension and cardiometabolic disorders and impaired cognition and emotional well-being, positioning sleep as a measurable biomarker as well as a therapeutic target.[1] Clinically, sleep disturbances are frequent in symptom-defined populations such as chronic pain, where prevalence estimates range from 67% to 88%, underscoring the need for scalable, accurate assessment strategies across routine care settings.[2]
The International Classification of Sleep Disorders provides a pragmatic taxonomy that is used in the sources underpinning this review, including ICSD-3 criteria for chronic insomnia and narcolepsy classification and ICSD-3-TR diagnostic framing for RBD.[13, 15, 18] For clinical decision-making, the present synthesis is organized around six ICSD-aligned groupings represented by the available evidence: insomnia disorder; sleep-related breathing disorders; central disorders of hypersomnolence; circadian rhythm sleep-wake disorders; parasomnias; and sleep-related movement disorders.[3–8]
2. Insomnia disorder
Definition and epidemiology
Insomnia is defined as difficulty initiating or maintaining sleep accompanied by daytime manifestations, and chronic insomnia diagnosis requires symptoms at least three times per week persisting for at least three months.[3, 13] Short-term insomnia symptoms occur in approximately 30% to 50% of adults, whereas up to 10% meet criteria for chronic insomnia, with higher prevalence in older individuals.[3] Across global studies, insomnia affects approximately 10% to 30% of the general population, and other estimates indicate that 6% to 15% of adults globally meet diagnostic criteria for chronic insomnia disorder, supporting substantial cross-cultural burden despite variability in ascertainment.[24, 25]
In primary care, insomnia is described as highly prevalent yet underdiagnosed and undertreated, and a National Sleep Foundation survey (N=1,506 US adults) reported that 70% of respondents stated clinicians never asked about sleep, highlighting a systematic missed opportunity for case-finding and management of a common, disabling condition.[23]
Pathophysiology
Insomnia is conceptualized as a hyperarousal disorder characterized by central and autonomic nervous system hyperactivation, with heightened cortical activity, increased metabolic rate, elevated heart rate, and increased sympathetic tone during hyperarousal states.[26] Chronic stress exposure can activate the HPA axis with increased secretion of CRH, ACTH, and cortisol, reinforcing and perpetuating cycles of insomnia and hyperarousal.[26] Progression from acute to chronic insomnia is described by the 3P model, in which predisposing, precipitating, and perpetuating factors influence brain centers that govern the production and persistence of insomnia symptoms.[13]
Mechanistic interest in the orexin (hypocretin) system reflects its role in wake promotion and vigilance-state control: orexin is a neuropeptide with two postsynaptic G-protein coupled receptors (OX1R and OX2R), and hypothalamic orexin neurons coordinate sleep–wake transitions and process metabolic, emotional, and circadian signals.[3, 26] Disruption or hyperactivity of the orexin system has been cited as a strong contributor to chronic insomnia, mainly through increased arousal and difficulty with sleep onset, providing a rationale for therapies that attenuate orexin-mediated wake drive rather than enhancing GABAergic sedation.[23, 26]
Diagnostic criteria and workup
Chronic insomnia diagnosis requires symptoms at least three times per week for at least three months in ICSD-3/DSM-5 aligned criteria, and routine assessment prioritizes a structured history of sleep disturbance type (delayed sleep onset, trouble staying asleep, early morning awakening, nonrestorative sleep), sleep routines and maladaptive habits, impaired daytime functioning, and potentially contributing comorbidities.[13, 23] Because other disorders can disrupt sleep, additional screening tools and laboratory or sleep studies may be required to rule out contributors such as mood disorders, pain, restless legs syndrome, or obstructive sleep apnea.[23]
Standardized symptom quantification commonly uses the Insomnia Severity Index (ISI), a 7-item self-report questionnaire assessing nighttime and daytime aspects over the past month, with results classifying insomnia as not present, mild, moderate, or severe.[23] Polysomnography is not usually necessary and is not recommended for the initial objective assessment of insomnia, reflecting the primacy of clinical diagnosis and targeted testing based on differential considerations.[23]
Evidence-based treatment
Clinical guidelines from major societies strongly recommend CBT-I as first-line therapy for insomnia, and evidence indicates CBT-I alone offers greater long-term efficacy than insomnia medications with few adverse effects.[23] Where pharmacotherapy is indicated, dual orexin receptor antagonists (DORAs) have emerged as a key mechanistically targeted class that improves insomnia by targeting the wakefulness system rather than the GABA system to increase sedation, with potential relevance to select comorbidity contexts.[23]
DORAs act by blocking both OX1R and OX2R, reducing wakefulness and promoting sleep, and by modulating a specific wake-promoting system they facilitate initiation and maintenance of sleep without significantly disrupting overall neurophysiological balance.[26, 27] In pooled/network evidence, DORAs were associated with improvement across analyzed efficacy outcomes, and a network synthesis reported that lemborexant 10 mg and suvorexant 20/15 mg produced the largest reductions in wake after sleep onset (WASO) at month 1, with standardized mean differences approximately -25 (with wide confidence intervals), though certainty for WASO was rated moderate due to inconsistency.[3] Adverse events commonly include somnolence, nasopharyngitis, and headache, with reported rates up to 14.8% in pooled analyses, emphasizing the need for individualized risk-benefit assessment.[3]
Daridorexant trials illustrate clinically operational thresholds and dose response. In these trials, clinical significance thresholds were specified as 20 minutes for objective WASO (PSG/actigraphy) and 30 minutes for subjective WASO, while LPS clinical significance was 10 minutes objectively and 20 minutes subjectively.[11] Daridorexant reduced WASO from baseline to days 1 and 2 in a dose-dependent fashion by 28.4, 32.3, 37.7, and 47.1 minutes in the 5, 10, 25, and 50 mg groups (p<0.001).[11] At least one adverse event was reported in 35%, 38%, 38%, 34%, 30%, and 40% of participants receiving daridorexant 5, 10, 25, 50 mg, placebo, and zolpidem, respectively, situating tolerability in an explicit comparative frame.[11]
The table below summarizes selected DORA efficacy and dosing points explicitly reported in the cited sources.
Latest advances and controversies
European guidance characterizes DORAs as the most significant recent development in the pharmacological treatment of insomnia while emphasizing that data remain to be validated through practical experience in everyday practice, reflecting the translational gap between controlled trials and heterogeneous real-world insomnia populations.[25] Across DORA trials, dosing appears to influence sleep maintenance, with higher doses correlating with longer total sleep time for each individual drug, supporting dose individualization as a core practical consideration.[3]
Evidence limitations constrain between-drug inference because direct comparisons across different DORAs are absent, and existing studies often include adult-only insomnia cohorts while excluding patients with important comorbidities, limiting generalizability to the complex multimorbidity seen in routine sleep clinics.[3] Subjective patient-reported sleep outcomes remain vulnerable to variability and uncertainty, a concern that persists even when such measures are widely used by the scientific community.[3] Early-phase pipeline development continues, including TS-142, described as a novel, potent DORA designed for fast absorption and a short plasma half-life, although early studies suffered high screen-failure rates (>90%), limiting generalizability and safety inference.[28]
Comorbidity and consequences
Insomnia is frequently comorbid with medical and psychiatric illnesses and remains underdiagnosed and undertreated in primary care, reinforcing the importance of systematic screening and integrated management rather than symptom-isolated prescribing.[23] Chronic insomnia is associated with downstream health consequences including increased incidence of heart diseases, diabetes, depression, anxiety, and a weakened immune system, and it produces daytime symptoms such as tiredness, difficulty concentrating, and mood changes that directly impair functioning.[26] Sleep disturbances are highly prevalent in major depressive disorder, with over 80% reporting significant sleep disturbance, and insomnia frequently precedes depressive episodes, predicting both initial development and recurrence, while persistent sleep disturbance after remission correlates with elevated relapse risk and reduced therapeutic responsiveness.[27]
3. Sleep-related breathing disorders
Definition and epidemiology
OSA is characterized by repetitive episodes of complete or partial collapse of the upper airway during sleep, causing intermittent hypoxia and fragmented sleep.[4] The global burden is large: OSA is estimated to affect one billion people, and OSAS is described as affecting approximately 936 million adults worldwide, including 425 million with moderate-to-severe disease, with frequent underdiagnosis despite substantial clinical consequences.[4, 12] Prevalence increases in men, older adults, and individuals with obesity, aligning with major demographic drivers of contemporary OSA epidemiology.[4]
OSAS contributes substantially to public-health burden through associations with daytime sleepiness, cognitive impairment, accident risk, metabolic dysfunction, and increased cardiovascular morbidity and mortality, and long-term cohort studies link untreated OSAS to a two- to threefold higher risk of stroke and all-cause mortality.[12]
Pathophysiology
OSA pathophysiology reflects the interaction of anatomical and functional factors leading to upper-airway collapse during sleep.[4] Anatomical contributors include narrow or collapsible airway anatomy, enlarged tonsils, a large tongue, and craniofacial abnormalities such as retrognathia and maxillary hypoplasia that reduce airway patency.[4] Functional factors include reduced neuromuscular control of airway muscles, low arousal threshold, and high loop gain, contributing to respiratory instability across sleep stages.[4]
Contemporary conceptual models emphasize four modifiable traits—pharyngeal collapsibility, neuromuscular compensation, loop gain, and arousal threshold—that explain heterogeneity in presentation and predict response to treatments, including greater response to mechanical splints/surgery/HNS when dominant anatomical collapse is present and potential benefit of respiratory-stabilizing strategies when loop gain is high.[12] Repetitive obstruction yields hypoxia–reoxygenation cycles that contribute to oxidative stress and systemic inflammation, and resultant sleep fragmentation and intermittent hypoxia affect multiple organ systems and increase risks of cardiovascular, metabolic, and neurocognitive impairment.[4]
Obesity amplifies OSA risk through fat accumulation around the upper airway, narrowing the pharyngeal lumen and increasing collapse propensity, and through reduced muscle tone that helps keep the airway open, particularly during REM sleep when muscle tone is physiologically reduced.[29] Obesity-associated chronic low-grade systemic inflammation may further influence upper-airway tissues and contribute to collapse, supporting a mechanistic bridge between metabolic disease and sleep-disordered breathing severity.[29]
Diagnostic criteria and workup
Clinical case-finding commonly uses screening instruments such as STOP-Bang, which has high sensitivity for detecting moderate-to-severe OSA but limited specificity, necessitating confirmatory testing, and NoSAS, which offers comparable diagnostic accuracy with fewer items.[12] Full overnight polysomnography remains the diagnostic gold standard, providing comprehensive evaluation of sleep stages, arousals, respiratory events, and comorbid sleep disorders.[12] To improve access, HSAT has gained acceptance for uncomplicated adults with suspected moderate-to-severe OSA, and evidence supports reliable performance in high-pretest probability populations; however, HSAT is less sensitive in mild OSA and may underestimate severity due to absent EEG sleep staging.[12]
In research-grade scoring, hypopneas may be defined using American Academy of Sleep Medicine rule 1B, requiring ≥30% reduction in airflow for ≥10 seconds with oxygen desaturation ≥4%, illustrating the operationalization of AHI components in contemporary trials including SURMOUNT-OSA.[10] Despite innovations, limitations remain in variability of sleep-apnea definition and classification across studies and in the limited accuracy of some devices in measuring all sleep stages, warranting caution when extrapolating wearable or simplified metrics to phenotyping or treatment decisions.[30]
Evidence-based treatment
CPAP remains the cornerstone and gold-standard therapy for OSA, with large randomized trials and meta-analyses demonstrating effectiveness in normalizing AHI, improving daytime sleepiness, and reducing blood pressure, particularly in resistant hypertension.[4, 12] Cardiovascular protection has been inconsistent across trials, with some failing to show reductions in hard outcomes such as myocardial infarction or stroke, and individual patient data meta-analyses indicate cardiovascular benefit is strongly adherence-dependent, with protective effects observed in patients using CPAP for more than four hours per night.[12] Adherence remains a principal limitation because discomfort, noise, and mask inconvenience can undermine sustained use despite objective efficacy.[4]
Alternatives and adjuncts include mandibular advancement devices, positional therapy, hypoglossal nerve stimulation, and surgery. Mandibular advancement devices are the most widely studied alternative to CPAP and improve daytime sleepiness and quality of life in mild-to-moderate OSA but typically produce smaller reductions in AHI compared with CPAP.[12] Positional OSA affects up to one-third of patients, and positional interventions can reduce AHI with selected improvements in sleepiness and quality of life, although long-term adherence is challenging with many patients discontinuing after several months.[12]
HNS has emerged as a promising therapy for PAP-intolerant patients with moderate-to-severe OSA who lack complete concentric palatal collapse, with reported significant AHI reduction and symptom improvement, but limitations include surgical invasiveness, high cost, and restricted eligibility criteria that limit widespread adoption.[12] Surgical approaches have variable efficacy: uvulopalatopharyngoplasty demonstrates variable efficacy with long-term relapse, whereas maxillomandibular advancement demonstrates the highest success rates with meta-analyses confirming long-term improvements in AHI and oxygenation, particularly in patients with craniofacial risk factors.[12]
Pharmacotherapy is used primarily for residual sleepiness or for disease modification through weight loss. Solriamfetol and pitolisant are approved for residual excessive daytime sleepiness despite PAP and improve functional outcomes without reducing AHI, aligning pharmacologic therapy with symptom targets rather than airway collapse mechanisms.[12] In long-term data, pitolisant reduced sleepiness over one year in adults with OSA, with pooled mean difference in ESS from baseline to one year of -8.0 (95% CI -8.3 to -7.5), and no cardiovascular safety issues reported in the cited analysis, while overall TEAE proportions were 35.1% and serious adverse events 2.0%.[31]
A major recent development is obesity-targeted incretin therapy for disease modification in OSA. In SCALE Sleep Apnea, liraglutide produced a greater reduction in mean AHI versus placebo (-12.2/h versus -6.1/h; 95% CI -11.0 to -1.2; p=0.015).[4] In SURMOUNT-OSA, tirzepatide reduced AHI at week 52 by -25.3 events/h versus -5.3 with placebo (treatment difference -20.0; 95% CI -25.8 to -14.2; p<0.001) in one trial and -29.3 versus -5.5 (treatment difference -23.8; 95% CI -29.6 to -17.9; p<0.001) in another, and up to 50.2% met combined criteria of AHI thresholds and ESS ≤10 relevant to clinical decision points where PAP may not be recommended.[10] Tirzepatide also reduced hypoxic burden, hsCRP concentration, and systolic blood pressure and improved sleep-related patient-reported outcomes in the cited trial report.[10] Adverse events were common in both tirzepatide and placebo groups but occurred more frequently with tirzepatide; the most frequently reported events were generally gastrointestinal, serious adverse events occurred in 7.5% overall, and there were two adjudicated confirmed cases of acute pancreatitis in one tirzepatide trial group with no reported medullary thyroid cancer cases in the provided text.[10]
Latest advances and controversies
Recent advances in OSA care include both therapeutic innovation and care-delivery redesign. SURMOUNT-OSA establishes incretin-based therapy as a high-impact, disease-modifying approach for obesity-associated OSA with substantial AHI reductions and clinically meaningful responder rates at 52 weeks.[10] At the same time, mechanisms by which GLP-1 receptor agonism influences respiratory control and upper-airway muscle tone remain unclear, and long-term efficacy and safety data in OSA populations are limited beyond available trial horizons.[4]
Implementation advances include telemonitoring of CPAP adherence, which provides real-time feedback and improves long-term usage, and virtual care pathways integrating screening questionnaires, HSAT, remote initiation, and digital adherence support, which may mitigate access barriers in resource-constrained or rural settings.[12] Persistent controversies include inconsistent cardiovascular endpoint evidence for CPAP—partly attributable to adherence variability—and the tendency of HSAT, oximetry, and wearables to underestimate OSA severity compared with PSG, particularly in mild OSA or in patients with comorbidities.[12] Trial-interpretation limits apply to incretin trials as well, including shorter duration designs not supporting assessment of long-term cardiovascular outcomes and uncertain minimum clinically important change thresholds for some patient-reported outcomes.[10]
Comorbidity and consequences
OSAS is associated with daytime sleepiness, cognitive impairment, accident risk, metabolic dysfunction, and increased cardiovascular morbidity and mortality, and untreated OSAS confers a two- to threefold higher risk of stroke and all-cause mortality in long-term cohort data.[12] Mechanistically, hypoxia–reoxygenation cycles contribute to oxidative stress and systemic inflammation, and sleep fragmentation and intermittent hypoxia increase risk of cardiovascular and metabolic disorders and neurocognitive impairment, providing a mechanistic bridge to observed epidemiologic outcomes.[4] Obesity-associated airway fat deposition and inflammatory influences on upper-airway tissues further reinforce the rationale for integrated cardiometabolic management aligned with OSA phenotypes.[29]
4. Central disorders of hypersomnolence
Definition and epidemiology
Narcolepsy is a rare but disabling neurological disorder involving disruption of the sleep–wake cycle and is often under- or misdiagnosed, and ICSD-3 classification divides narcolepsy into type 1 and type 2.[5, 15] Onset commonly occurs in adolescence or early adulthood, yet diagnosis is typically delayed by 8–12 years, reflecting persistent barriers to recognition and confirmatory testing access.[14] The classic NT1 symptom profile includes excessive daytime sleepiness, cataplexy, disrupted nocturnal sleep, sleep paralysis, and hypnagogic/hypnopompic hallucinations.[15]
Pathophysiology
Narcolepsy pathophysiology is primarily associated with loss of hypocretin (orexin) neurons, involving autoimmune and genetic risk factors particularly for NT1.[5] Loss of hypocretin neurons leads to reduced and inconsistent firing of wake-promoting neurons and unstable transitions between wakefulness and sleep, providing a mechanistic substrate for excessive daytime sleepiness.[9] NT1 is characterized by cataplexy and significantly reduced CSF orexin levels, with a cited threshold of CSF hypocretin-1 <110 pg/mL.[15]
Genetic susceptibility and autoimmune mechanisms are emphasized, including HLA-DQB1*06:02 association and orexin-specific T cell-mediated neuronal damage, with environmental triggers such as H1N1 influenza infection or vaccination; supporting epidemiology includes a marked increase in narcolepsy incidence among children and adolescents infected with H1N1 or receiving the Pandemrix vaccine.[9, 15] Cataplexy is conceptualized as intrusion of REM atonia circuitry into wakefulness, aligning clinical phenomenology with REM state-dissociation mechanisms.[9]
Diagnostic criteria and workup
Persistent and severe excessive daytime sleepiness lasting longer than three months warrants thorough evaluation for narcolepsy, with initial assessment including subjective measures such as the Epworth Sleepiness Scale and Stanford Sleepiness Scale.[9] Diagnostic confirmation involves overnight polysomnography to assess sleep architecture and exclude other sleep disorders contributing to sleepiness, followed by next-day MSLT.[9] Narcolepsy is confirmed when mean sleep latency is less than eight minutes and at least two sleep-onset REM periods are observed across five nap opportunities.[9]
MSLT sensitivity is approximately 85% in patients exhibiting cataplexy, and in inconclusive cases CSF hypocretin-1 testing may support diagnosis: in narcolepsy with cataplexy, CSF hypocretin-1 concentrations ≤110 pg/mL are associated with high diagnostic specificity (99%) and sensitivity (87%) in the cited summary.[9]
Evidence-based treatment
The primary goal of narcolepsy treatment is symptom management enabling participation in daily home and occupational activities, and behavioral strategies such as scheduled naps of about 20 minutes can significantly reduce sleep episodes during waking hours.[9] Combined approaches integrating pharmacologic therapy with two scheduled 15-minute naps per day and consistent nocturnal sleep hygiene yield superior outcomes in mitigating subjective excessive daytime sleepiness and sleep attacks compared with pharmacotherapy alone.[9]
For excessive daytime sleepiness, commonly used agents include modafinil, armodafinil, methylphenidate, and more recently solriamfetol, with pitolisant also approved for EDS or cataplexy in adult patients with narcolepsy.[5, 9] Randomized trial evidence summarized for modafinil indicates ESS reductions of 4–6 points (p<0.001) and MWT sleep-latency prolongation of 3–5 minutes (p<0.001), with adult dosing described as starting at 100 mg/day and increasing to 200–400 mg/day if needed.[15] For solriamfetol, phase III trials reported mean MWT increases of 9.8 and 12.3 minutes versus 2.1 for placebo and ESS reductions of 5.4 and 6.4 points versus 1.6 for placebo at 150 mg and 300 mg doses, respectively.[15]
Pitolisant efficacy in cataplexy and sleepiness is supported by Harmony-CTP findings: 36 mg/day significantly reduced ESS by 5–7 points (p<0.001), prolonged MWT by 4–6 minutes (p<0.001), and decreased weekly cataplexy episodes by 75% (p<0.001).[15] Sodium oxybate is described as the only agent that simultaneously improves excessive daytime sleepiness, cataplexy, and disrupted nighttime sleep, with adult starting dose 4.5 g/night titratable to 9 g/night and long-term use associated with a significant sodium load of 1100–1640 mg/night, which poses potential cardiovascular risks in susceptible patients.[15]
Latest advances and controversies
A central pharmacologic development direction is mechanism-based orexin replacement via orexin-2 receptor agonism, positioned as a potential shift from symptomatic wake promotion toward pathophysiology-targeted therapy in hypocretin-deficient narcolepsy, but current clinical studies lack head-to-head comparisons with comparable agents.[15] Hepatic safety remains a salient development risk for this class, with a cited trial terminated early due to five cases of significant liver enzyme elevation and three cases meeting Hy’s law criteria for drug-induced liver injury.[15]
Diagnostic delay remains a persistent clinical and socioeconomic challenge: underdiagnosis and late or misdiagnosis can extend diagnostic delay up to 14 years and is associated with reduced quality of life, psychological distress, higher unemployment, and increased road accident risk during the delay interval.[32]
Comorbidity and consequences
Narcolepsy confers elevated accident risk: patients are reported to be three to four times more likely to be involved in motor vehicle accidents compared with the general population.[9] During diagnostic delay, negative consequences include lower quality of life and psychological distress alongside higher unemployment and increased road accident risk, reinforcing the clinical value of earlier recognition and referral for PSG/MSLT confirmation when excessive daytime sleepiness persists.[32] Comorbidity is common in real-world cohorts, with one summary reporting that 63.4% of patients presented with at least one comorbidity.[32]
5. Circadian rhythm sleep-wake disorders
Definition and epidemiology
Circadian rhythm sleep-wake disorders arise when the internal physiological clock is not synchronized with external stimuli, disrupting the sleep–wake cycle and other circadian-regulated activities.[33] They may be classified as endogenous (including delayed and advanced sleep-wake phase disorder, non-24-hour sleep-wake rhythm disorder, and irregular sleep-wake rhythm disorder) or exogenous (associated with shift work or jet lag).[6]
DSWPD is characterized by a delay in the main sleep period with difficulty falling asleep and waking at socially appropriate times, and ICSD-3 criteria specify that the delay is recurrent for at least three months and not better explained by another sleep, mental, or medical disorder.[17] An estimated 7% to 16% of adolescents and young adults are affected by DSPS/DSWPD, indicating a high prevalence in developmental windows with strong social timing constraints.[16] SWSD is a subtype of circadian rhythm sleep disorder caused by recurring work schedules that conflict with natural sleep–wake patterns, and up to one-third of shift workers may experience persistent symptoms including delayed sleep initiation, fragmented sleep, excessive tiredness during wake periods, and compromised cognitive performance.[34]
Pathophysiology
The suprachiasmatic nucleus serves as the master clock synchronizing internal processes with external events and receives light signals through the eyes, establishing a light-driven entrainment mechanism that underpins both physiologic rhythm stability and vulnerability to misalignment.[6, 33] Melatonin secretion is closely related to the light–dark cycle and is described as an important regulator of the human biological clock, rising after dusk and peaking between 2:00 and 4:00 a.m. with suppression during daylight, providing a measurable endocrine signature of circadian phase.[6]
In DSWPD, delayed circadian phase is assessed via physiologic markers such as core body temperature minimum or dim light melatonin onset, and delayed DLMO is described as highly sensitive and specific for DSWPD and useful for distinguishing it from extrinsic circadian or non-circadian causes that can present similarly, such as jet lag or primary insomnia.[17] DSWPD is associated with decreased total sleep time and sleep efficiency and longer sleep onset latency even at preferred bedtimes, and sleep homeostatic responses differ, with patients less likely to have daytime recovery sleep or to advance the sleep period following sleep deprivation.[17]
In shift workers, melatonin production is often misaligned or suppressed due to atypical light exposure patterns, and mechanistically melatonin interacts with MT1 and MT2 receptors in the SCN to modulate the internal clock and facilitate circadian realignment, aligning receptor biology with therapeutic rationale for timed melatonin administration and light management.[34] Receptor biology is further differentiated in the cited material: MT1 receptor activation is described as mainly involved in REM sleep regulation, while MT2 receptors influence NREM sleep, supporting pharmacologic interest in receptor-targeting approaches to specific sleep disorders.[6]
Diagnostic criteria and workup
Clinical assessment of DSWPD emphasizes stable patterns of delayed sleep and wake timing relative to social expectations, with sleep length otherwise normal and sleep quality normal after sleep onset, persisting for at least three months.[16] Objective assessment of delayed phase may be made by recording sleep and activity, by self-assessment of diurnal preference, or by measuring physiologic variables, most often CTmin or DLMO from the evening melatonin surge.[17] DLMO is a commonly used measure, and its delayed timing is highlighted as a high-utility discriminator for DSWPD relative to mimics, supporting biomarker-anchored phenotyping when available.[16, 17]
Longitudinal monitoring can use sleep diaries, and actigraphy-based methods for assessing sleep patterns and circadian rhythms in DSPS are under development and validation, while EEG and PSG have been used to examine sleep stage transitions and spindles as neurophysiologic markers in DSPS, supporting multi-modal assessment in selected cases.[16]
Evidence-based treatment
Circadian treatment is phase-directed. Morning exposure to bright light shortly after CTmin advances circadian phase and sleep period according to a phase response curve, whereas evening light can suppress melatonin production and make it harder to fall asleep, establishing a mechanistic basis for light timing prescriptions.[16, 17] Exogenous melatonin administration is a recommended treatment for DSWPD under cited guidelines, and melatonin shifts phase according to a phase response curve roughly inverse to light, with early-evening dosing prior to DLMO advancing circadian phase; typical dosages range from 0.5 to 5 mg taken 30 minutes to 2 hours before bedtime.[16, 17]
For SWSD, subjective sleep quality was consistently reported to improve when melatonin was taken approximately 30 to 60 minutes before the intended sleep period, with doses ranging from 2 mg to 5 mg across immediate-release and extended-release formulations in the cited synthesis, although heterogeneity limited formal meta-analysis in that body of evidence.[34] Personalized light therapy anchored to DLMO estimation and confirmation has proof-of-concept trial support: participants receiving personalized light therapy achieved a larger phase delay (Mean 7.37 hours) than non-personalized control (Mean 0.84 hours) with t(5)=2.501 and p=0.05, and preliminary results suggest personalization may more effectively correct circadian misalignment by delivering treatment according to individual circadian phase.[35]
Hypnotic agents may be used to promote and maintain sleep, but there is little evidence supporting treatment of DSWPD using hypnotics, and the literature notes that even if hypnotics can advance sleep onset, studies are lacking on their effects on circadian phase and sleep homeostasis, reinforcing the distinction between hypnotic sedation and true circadian realignment.[17]
Latest advances and controversies
DLMO is emphasized as a sensitive and specific biomarker for DSWPD and a tool for differential diagnosis, and biomarker-anchored personalization can be operationalized through wearable-derived DLMO estimation confirmed with in-lab DLMO, as demonstrated in a randomized personalized light schedule intervention using Apple Watch activity data and app-delivered protocols.[17, 35] For melatonin in delayed sleep phase disorder, reviews reported improvement in sleep-onset latency and in some cases advancement in melatonin onset time, but heterogeneity in timing and outcomes across trials was substantial and a need for more updated evidence was explicitly identified in the cited umbrella review.[36]
Comorbidity and consequences
Untreated DSPS/DSWPD can have severe consequences including impaired cognitive function, mood disturbances, and increased risk of sleep-related problems such as sleep apnoea and insomnia, and circadian misalignment is associated with insomnia and/or daytime sleepiness resulting in impairment of daytime function.[16, 17] For shift work, chronic circadian disruption has been implicated in insulin resistance, cardiovascular disorders, gastrointestinal dysregulation, and weakened immune defenses, and reduced alertness due to inadequate sleep contributes to increased workplace errors and accidents in safety-critical industries.[34] Epidemiologic studies cited report that shift workers have about a 40% higher risk of heart disease compared with day workers, and circadian disruption affects glucose metabolism and cytokine expression including IL-6 and IL-10, with additional reported reproductive, immune, and cancer-related associations including IARC classification of shift work/circadian disturbance as carcinogenic factors in 2007.[37]
6. Parasomnias
Definition and epidemiology
Parasomnias are sleep disorders involving unusual motor and vocal behaviors accompanied by emotional or sensory perceptions and associated with dream mentation, and RBD is a REM-related parasomnia characterized by enacted dream episodes due to loss of physiological REM atonia.[7] RBD is further described as a condition in which generalized skeletal muscle atonia of REM sleep is compromised, allowing injurious acting-out of dreams, situating the syndrome in a mechanistic framework of REM motor disinhibition.[19]
Epidemiologically, general-population prevalence is estimated at approximately 0.5% to 1%, with clear male predominance and peak incidence beyond age 50, and pooled literature describes 87.2% male representation and mean age of 63.6 years across included reports.[7, 18] Community-based polysomnographic studies reported idiopathic RBD prevalence rates of 1.06% and 1.23% in Switzerland and Japan, with additional estimates of 1.34% in a Korean cohort and 0.74% in a Spanish primary-care cohort of adults older than 60 years.[19] RBD and its hallmark on polysomnography (loss of REM atonia) are common in synucleinopathies, occurring in 30%–70% of Parkinson disease, 70%–80% of dementia with Lewy bodies, and 70%–90% of multiple system atrophy, and in many cases RBD precedes other disease manifestations and is then termed idiopathic/isolated RBD.[38]
Pathophysiology
The defining pathophysiology of RBD is loss of REM atonia, permitting dream enactment during REM sleep.[7, 19] RBD is tightly linked to prodromal α-synucleinopathy risk: longitudinal studies on iRBD have found that over 90% of patients eventually phenoconvert to an overt α-synucleinopathy, and other longitudinal cohort summaries indicate that 80% to 90% develop one of these disorders within 10 to 15 years.[18, 19]
Neuroimaging synthesis supports a multi-system neurodegenerative process, reporting alterations in dopaminergic and cholinergic systems, blood perfusion, and glucose metabolism in RBD and PD with RBD, with structural and functional changes involving nigrostriatal, limbic, and cortical networks; a longitudinal study suggested an ordering in iRBD where striatal synaptic dopaminergic dysfunction occurs first, followed by abnormal iron metabolism in substantia nigra pars compacta coupled with neuromelanin changes.[39]
Diagnostic criteria and workup
ICSD-3-TR-aligned diagnostic criteria require repeated episodes of complex motor or vocal behaviors associated with vivid or violent dreams, polysomnographic confirmation of REM sleep without atonia, exclusion of other potential causes, and evidence of clinically significant consequences such as injuries or disturbed sleep.[18] Operational diagnostic criteria specify that repeated episodes of sleep-related vocalization or complex motor behaviors must be documented by video-polysomnography during REM sleep (or presumed REM sleep based on clinical history), with PSG demonstrating REM sleep without atonia and with disturbances not better explained by another sleep or mental disorder.[19]
In the cited evidence base, diagnostic methods required at least one night of vPSG registration, and vPSG is described as the gold standard for differential diagnosis between RBD and other sleep disorders.[7] Clinically, individuals may awaken quickly and become rapidly alert with coherent dream recall, but retrospective dream collection is vulnerable to recall bias, reflecting a methodological limitation in oneiric-content research and symptom characterization.[7, 19] Differential diagnosis includes NREM parasomnias, obstructive sleep apnea pseudo-RBD, sleep-related periodic limb movement disorder pseudo-RBD, and nocturnal seizures, reinforcing the need for vPSG in diagnostic confirmation and exclusion of mimics.[19]
Evidence-based treatment
Management begins with injury prevention: maintaining a safe sleeping environment is recommended to prevent potentially injurious nocturnal behaviors.[19] Pharmacotherapy recommendations for adults with iRBD or secondary RBD include clonazepam, immediate-release melatonin, and pramipexole (for iRBD), with AASM characterizing these as conditional recommendations and emphasizing clinician judgment and patient values and preferences in selecting therapy.[19] Longitudinal studies in the cited summary suggest melatonin and clonazepam reduce frightening or violent dreams and nightmares during treatment, supporting symptom-targeted therapy in parallel with safety measures.[7]
Latest advances and controversies
RBD provides an opportunity to test potential treatments at the earliest stages of synucleinopathy, but to date all neuroprotective disease-modifying therapies for synucleinopathies have failed, potentially because pathologic changes at clinical diagnosis are already too advanced or not modifiable.[40] A central barrier is biomarker absence: there are no established or widely used biomarkers for detecting prodromal synucleinopathies, motivating intensive biomarker development and risk stratification strategies in prodromal cohorts.[40]
Prognostic quantification is increasingly refined. A Movement Disorders Society consensus statement concluded that iRBD proven by vPSG has the highest likelihood ratio for Parkinson disease phenoconversion (LR = 130), and meta-analysis conversion rates were reported as 33%, 82%, and 97% at 5, 10.5, and 14 years, respectively, supporting iRBD as a high-yield population for prevention trials and for counseling about neurodegenerative risk.[19] Phenotypic heterogeneity remains unresolved, including uncertainty whether antidepressant-associated RBD unmasks the same neuropathologic process as typical RBD or reflects different pathophysiology, and dream-frequency research is limited by retrospective recall bias with calls for prospective experimental designs.[7, 40]
Comorbidity and consequences
iRBD carries high neurodegenerative risk: over 90% phenoconvert in longitudinal studies, and meta-analytic conversion reaches 97% at 14 years, supporting RBD as a major prodromal marker of α-synucleinopathy in clinical counseling and research enrichment.[19] Immediate consequences also include potential injury from dream-enactment behaviors, reinforcing safety interventions as first-line management.[19] In prodromal cohorts, subtle neurological dysfunction is frequent, with one cohort reporting 84% having an abnormality in at least one neurological domain, supporting systematic neurological assessment in iRBD evaluation and longitudinal follow-up.[40]
7. Sleep-related movement disorders
Definition and epidemiology
RLS is a chronic neurological disorder in which many individuals also experience periodic limb movements of sleep, described as involuntary, rhythmic leg jerks during sleep occurring in up to 80% to 90% of RLS patients, contributing to sleep fragmentation though PLMS are not specific to RLS.[8] Population studies in North America report roughly 10% of adults experience RLS symptoms, with around 2% to 3% having clinically significant symptoms frequent or severe enough to require treatment, while pooled prevalence estimates vary by diagnostic methods and criteria stringency.[8, 20] One corrected pooled prevalence estimate was 3% (95% CI 1.4–3.8), with higher pooled prevalence in females (4.7%) than males (2.8%), consistent with sex differences and increased prevalence with age described across sources.[20, 22] Pregnancy is a strong precipitant, with approximately one-third of women experiencing RLS in the third trimester, and higher parity is associated with increased risk, potentially contributing to female predominance.[8]
RLS prevalence is increased in chronic kidney disease and dialysis populations: a majority of dialysis studies report prevalence between 15% and 30%, and updated review conclusions indicate RLS is two to three times more common in CKD patients than the general population; in ESRD, prevalence ranges from 15% to 45% with highest rates in hemodialysis patients, and uremic RLS is associated with chronic insomnia affecting up to 70% of cases.[21, 41]
Pathophysiology
RLS is framed as a circadian dysfunction of sensorimotor integration, and current models emphasize two interconnected central mechanisms: brain iron deficiency and dopaminergic dysfunction.[8, 22] Brain iron deficiency and dopaminergic neurotransmission abnormalities are described as central in pathogenesis, and dopaminergic agents improve symptoms, supporting a dopaminergic contribution even when not solely attributable to CNS dopaminergic deficiency.[22, 41]
Peripheral iron measures may not capture central iron deficiency: serum ferritin and percent transferrin saturation do not accurately reflect brain iron stores, and serum iron deficiency is present in only 25% to 44% of patients in the cited summary, while CSF transferrin and ferritin changes can be consistent with CNS iron deficiency even when peripheral measures are normal.[22] The cited mechanistic framing emphasizes synaptic iron as the critical factor correlating with symptoms, motivating therapeutic focus on iron repletion even when traditional systemic indices appear borderline.[22]
Genetic predisposition is substantial, with 83% concordance reported in monozygotic twins and genome-wide association studies identifying at least eight implicated loci, with one GWAS identifying BTBD9, MEIS1, MAP2K5, PTPRD, and TOX3 as contributing to increased risk and accounting for a large proportion of population genetic risk in the cited report.[22] Additional proposed mechanisms include hypoxic-state activation with elevated hypoxia-inducible factors and VEGF in microvasculature, a hypo-adenosinergic state with low adenosine promoting hyperarousal, and hyperglutamatergic neurotransmission reflected by elevated thalamic glutamate and supported by therapeutic effects of α2δ ligands in the cited mechanistic synthesis.[8, 22, 42] Neurophysiologically, PLMS occur in up to 85% of patients, providing an objective sleep-related movement signature that can be captured by PSG when clinically indicated for sleep fragmentation differential diagnosis.[42]
Diagnostic criteria and workup
RLS diagnosis relies on meeting five essential IRLSSG criteria, and the 2012 revision emphasized differentiating true RLS from common mimics such as positional discomfort, leg cramps, arthritis, and anxiety, strengthening diagnostic specificity and influencing prevalence estimates across studies.[20, 22] For quick screening, the IRLSSG recommends a single validated question about unpleasant, restless leg feelings during evening relaxation or sleep that are relieved by movement, with reported sensitivity 100% and specificity 96.8% in large-scale screening contexts.[22]
Initial management includes measuring serum ferritin and transferrin-percent saturation, with iron replacement indicated when measures are below the low-to-normal range and with recommendations to raise ferritin above 75 ng/mL, while acknowledging that serum markers may not accurately reflect brain iron stores and that CSF ferritin and transferrin may serve as promising biomarkers for diagnosis and management.[22, 41, 42] For PLMS assessment, actigraphy is no longer recommended owing to diagnostic-accuracy concerns, and polysomnography is the only recommended option for PLMS assessment, though it is not part of the standard diagnostic process for RLS itself.[42]
Evidence-based treatment
Treatment should be initiated when symptoms impair quality of life, daytime functioning, social functioning, or sleep, and iron deficiency is a strong risk factor with studies demonstrating that iron supplementation improves characteristic neurological symptoms.[20, 42] Clinical guidelines recommend IV ferric carboxymaltose for adults with moderate-to-severe RLS with serum ferritin levels ≤300 μg/L and TSAT below 45%, and emphasize that both oral and IV iron should be limited to TSAT <45% to avoid iron overload.[22] IV iron therapy, particularly FCM, has demonstrated superior efficacy in alleviating RLS symptoms, and IV iron is described as especially effective in patients with serum ferritin levels exceeding 75 μg/L, whereas oral iron provides little benefit; oral iron effectiveness may be limited by poor absorption and compliance issues including gastrointestinal discomfort.[22]
Pharmacotherapy has shifted due to augmentation risk. Dopamine agonists, previously considered first-line therapy, are now conditionally recommended because of symptom augmentation over time, and augmentation rates increase with study duration, with short-term rates <10% reported and longer-term estimates varying substantially; in ESRD/uRLS, augmentation develops in 40%–70% on dopamine agonists and up to 80% on levodopa in the cited summary.[20, 21, 42] α2δ ligands exhibit minimal augmentation risk, and in ESRD populations pregabalin maintains a favorable safety profile with straightforward dose adjustment for renal clearance.[21] In a randomized placebo-controlled ESRD uRLS trial, pregabalin produced a median severity reduction of -5.0 points at week 6 versus 0.0 with placebo (p≤0.001) and -9.0 versus -2.0 at week 12 (p≤0.001), with mild sedation reported in 28% of pregabalin-treated patients and no serious adverse events attributable to pregabalin in the cited report.[21]
Second-line therapies in CKD-related RLS include IV iron in those intolerant of oral iron and/or those with augmentation and severe symptoms and opioids including tramadol, oxycodone, and methadone, reflecting escalation pathways for refractory disease.[41] Long-term data on safety and efficacy of repeated treatments, particularly repeated IV iron, are described as sparse, and non-response despite ferritin normalization is documented, with nearly two-thirds of women with iron-deficient RLS continuing to experience symptoms despite normalization in one report, supporting the need for mechanistic stratification beyond peripheral iron indices.[22]
Latest advances and controversies
Revised IRLSSG criteria and improved differentiation from mimics partly explain heterogeneous prevalence estimates, with prevalence tending to be lower in studies using more accurate diagnostic methods and generally lower in East and Southeast Asia compared with other regions in the cited synthesis.[20] Augmentation prevalence remains controversial and varies by drug, dose, duration, study type, and criteria used to evaluate augmentation, complicating comparative decision-making and motivating guideline emphasis on non-dopaminergic first-line strategies.[20, 42]
Biomarker and mechanistic advances include interest in CSF ferritin and transferrin as promising markers for RLS diagnosis and management given discordance between serum and brain iron stores, and electrophysiologic work suggests that cortical oscillatory profiling may serve as a rational preclinical screening tool for identifying promising RLS therapeutic candidates before exposure of high-risk populations to clinical trials.[21, 22] Ongoing randomized double-blind studies in CKD-associated RLS assessing ropinirole and pramipexole underscore continuing comparative-therapy uncertainty in renal populations where augmentation and comorbidity burden are high.[41]
Comorbidity and consequences
In uremic/ESRD-associated RLS, disrupted sleep architecture is prominent, with chronic insomnia affecting up to 70% and sleep deprivation cascading into daytime fatigue, depression, anxiety, and marked functional impairment in the cited report.[21] Recent cohort studies cited indicate uRLS independently predicts cardiovascular events and increased mortality in dialysis populations, suggesting that inadequately treated uRLS may accelerate already elevated mortality risk in ESRD.[21] In CKD-associated RLS, patients demonstrate increased mortality and increased incidence of cardiovascular accident, depression, insomnia, and impaired quality of life compared with CKD without RLS, and there is evidence that chronic RLS predisposes to cardiac and cerebrovascular accidents while acknowledging a need for more careful studies.[41]
8. Cross-cutting advances
Sleep measurement and phenotyping are increasingly shaped by the tension between PSG’s diagnostic richness and its scalability limits. PSG remains the gold standard but its complexity, high cost (USD 1500–2000 per night in the United States), need for qualified personnel, and artificial clinical setting limit broad application, motivating development of home-based and wearable solutions.[1] Actigraphy infers sleep continuity based on assumptions of sleep within a time frame and uses movement thresholds to indicate awakenings, with high sensitivity (>90%) but low specificity for wakefulness (20%–70%), limiting utility in populations with frequent pre- and mid-sleep wakefulness such as chronic pain.[2]
Wearable EEG and wearable PSG platforms are increasingly specified in clinical-translation literature. Examples include the Dreem Headband with five carbon-infused dry electrodes at F7, F8, Fpz, O1, and O2 sampling at 250 Hz and integrating accelerometry and pulse oximetry, and the Sleep Profiler X4 using three frontopolar electrodes (AF7, AF8, Fpz) with cloud transmission and accelerometer-based movement tracking.[1] Wearable PSG data can assess sleep continuity, sleep stages, and EEG power spectrum with similar accuracy (>80%) as lab-based PSG in cited reports, yet validation standardization is emphasized as insufficient, and algorithmic discrepancies such as systematic overestimation of REM and underestimation of deep stage N3 can distort clinical interpretation.[1, 2]
Across disorders, bidirectional comorbidity frameworks are increasingly used to interpret symptom clusters and to prioritize integrated care pathways. Sleep disturbance and chronic pain share a bidirectional relationship in which poor sleep exacerbates pain and pain disrupts sleep, and sleep deprivation can increase pain sensitivity and hinder pain modulation, underscoring a rationale for longitudinal objective monitoring when feasible.[2]
9. Diagnostic tools at a glance
PSG remains the gold standard for comprehensive sleep assessment but is limited by cost and operational barriers, supporting selective rather than universal deployment.[1] HSAT improves access for uncomplicated adults with suspected moderate-to-severe OSA and performs reliably in high-pretest probability patients but is less sensitive in mild OSA and may underestimate severity due to absent EEG staging, a limitation shared by many simplified and wearable approaches.[12] For central hypersomnolence, PSG followed by MSLT provides objective confirmation, with narcolepsy criteria requiring mean sleep latency <8 minutes and ≥2 SOREMPs across five nap opportunities, and CSF hypocretin-1 ≤110 pg/mL provides high-specificity support in NT1 with cataplexy.[9] For circadian rhythm disorders, sleep diaries/actigraphy and biomarker-phase measures such as DLMO and CTmin quantify phase delay and help distinguish DSWPD from mimics; delayed DLMO is described as highly sensitive and specific for DSWPD.[16, 17] For parasomnias, vPSG is the gold standard for RBD diagnosis and differential diagnosis, requiring REM sleep without atonia documentation and exclusion of mimics such as NREM parasomnias or pseudo-RBD from OSA or PLMS.[7, 19] For RLS, diagnosis is clinical via IRLSSG criteria with iron studies as a core workup component and PSG reserved for PLMS characterization when clinically necessary.[22, 41, 42]
10. Therapeutics pipeline 2024–2025
Mechanism-directed therapeutics increasingly target specific neurobiological systems implicated in sleep–wake regulation and disorder pathogenesis. In insomnia, orexin-system modulation remains central: DORAs block OX1R and OX2R to reduce wakefulness and promote sleep, and early pipeline agents such as TS-142 are designed for fast absorption and short plasma half-life, though early studies face generalizability limits due to high screen-failure rates.[26, 28] In OSA, disease modification through obesity-targeted incretin therapy has phase 3 evidence of substantial AHI reductions at 52 weeks with tirzepatide, while mechanistic uncertainty and limited long-term safety/outcome data remain active questions.[4, 10]
In narcolepsy, orexin-2 receptor agonism represents an emerging mechanism-based approach, but hepatic safety signals have terminated at least one development program and head-to-head comparative evidence among OX2R agonists is lacking in current clinical studies.[15] In RLS, guideline-concordant pipelines emphasize iron repletion strategies including IV ferric carboxymaltose where indicated and non-dopaminergic symptom control given augmentation risks associated with dopamine agonists, with ongoing randomized trials in CKD-associated RLS addressing unresolved comparative questions in renal populations.[20, 22, 41]
11. Practice points and knowledge gaps
Clinical practice requires high-specificity diagnostic reasoning paired with pragmatic access pathways. The following points synthesize actionable steps and unresolved questions grounded in the cited evidence.
Chronic insomnia should be identified using ICSD-3/DSM-5-aligned frequency and duration criteria (≥3 times/week for ≥3 months) and quantified with ISI severity bands, while recognizing that PSG is not recommended for initial objective assessment unless needed for differential diagnosis.[13, 23]
CBT-I should be first-line for insomnia given superior long-term efficacy and few adverse effects, with DORAs as a mechanistically targeted pharmacologic option that improves efficacy outcomes and reduces WASO in trial syntheses, while acknowledging moderate certainty for WASO and absence of direct head-to-head DORA comparisons.[3, 23]
OSA case-finding can use STOP-Bang or NoSAS but requires confirmatory testing; PSG remains gold standard while HSAT improves access for uncomplicated moderate-to-severe suspected OSA yet may underestimate severity in mild disease due to absent EEG sleep staging.[12]
CPAP is highly effective for AHI normalization and symptom improvement, but cardiovascular benefit is inconsistent and appears adherence-dependent with benefit observed >4 hours/night; telemonitoring and virtual pathways can improve long-term usage and access.[12]
For obesity-associated moderate-to-severe OSA, tirzepatide has phase 3 evidence of large AHI reductions at 52 weeks and clinically meaningful responder rates, but trial duration limits long-term cardiovascular outcome assessment and mechanisms beyond weight loss remain incompletely defined.[4, 10]
For suspected narcolepsy, evaluation should follow persistent severe EDS >3 months with PSG followed by MSLT criteria (mean sleep latency <8 minutes and ≥2 SOREMPs), with CSF hypocretin-1 ≤110 pg/mL supporting NT1 diagnosis with high specificity/sensitivity in cataplexy cases; diagnostic delay remains a major quality-of-life and safety problem.[9, 32]
DSWPD diagnosis benefits from phase documentation via DLMO or CTmin, with delayed DLMO described as highly sensitive and specific; treatment should prioritize timed morning light and timed melatonin (0.5–5 mg 30 minutes to 2 hours before bedtime) rather than hypnotics, which have little evidence for phase shifting.[16, 17]
RBD requires vPSG documentation of REM sleep without atonia and exclusion of mimics; counseling should address high phenoconversion risk to synucleinopathy (e.g., meta-analytic conversion 33%, 82%, 97% at 5, 10.5, 14 years) and immediate injury prevention via safe sleep environment, with conditional pharmacotherapy options including clonazepam and immediate-release melatonin.[7, 19]
RLS diagnosis should use IRLSSG criteria and explicit mimic exclusion, with iron studies (ferritin and TSAT) in initial workup; treatment should emphasize iron repletion (including IV FCM under ferritin/TSAT thresholds) and α2δ ligands given augmentation risks of dopamine agonists, while recognizing limited long-term data for repeated IV iron and potential non-response despite ferritin normalization.[20–22, 41]
Conclusions
Across ICSD-aligned disorder categories, contemporary sleep medicine increasingly prioritizes mechanistic specificity, phenotype-aware diagnostics, and scalable monitoring strategies. Insomnia models emphasize hyperarousal and orexin-mediated wake drive with CBT-I as first-line and DORAs as a major pharmacologic advance requiring further validation in real-world multimorbidity populations.[23, 25, 26] OSA management is evolving from exclusive reliance on mechanical splinting toward endotype-aware frameworks and disease modification through metabolic therapy, while implementation innovations address adherence and access constraints and diagnostic innovations require cautious validation against PSG.[10, 12] Central hypersomnolence care retains PSG–MSLT-centric diagnostics and symptom-targeted therapeutics while advancing toward orexin replacement strategies constrained by safety and comparative-evidence gaps.[9, 15] Circadian medicine is moving toward biomarker-anchored personalization using DLMO-driven light and melatonin prescriptions, and parasomnia research increasingly leverages iRBD as a high-risk prodromal synucleinopathy cohort despite a lack of established prodromal biomarkers.[17, 19, 35, 40] In sleep-related movement disorders, iron biology and augmentation-aware prescribing have shifted practice toward iron repletion and α2δ ligands with continued need for long-term outcome data and biomarker stratification beyond peripheral iron indices.[20, 22]
Glossary of abbreviations
- AHI: apnea–hypopnea index.[10]
- AASM: American Academy of Sleep Medicine.[10]
- ACTH: adrenocorticotropic hormone.[26]
- CBT-I: cognitive behavioral therapy for insomnia.[23]
- CPAP: continuous positive airway pressure.[12]
- CRH: corticotropin-releasing hormone.[26]
- CRSWD: circadian rhythm sleep-wake disorders.[6, 33]
- CTmin: minimum core body temperature timing.[17]
- DLMO: dim light melatonin onset.[16, 17]
- DORAs: dual orexin receptor antagonists.[23, 26]
- DSWPD or DSPS: delayed sleep-wake phase disorder / delayed sleep phase syndrome.[16, 17]
- EDS: excessive daytime sleepiness.[15]
- ESS: Epworth Sleepiness Scale.[9]
- FCM: ferric carboxymaltose.[22]
- HNS: hypoglossal nerve stimulation.[12]
- HSAT: home sleep apnoea testing.[12]
- HPA axis: hypothalamic–pituitary–adrenal axis.[26]
- ICSD: International Classification of Sleep Disorders.[7, 13, 15]
- IRLSSG: International Restless Legs Syndrome Study Group.[22]
- ISI: Insomnia Severity Index.[23]
- LPS: latency to persistent sleep.[11]
- MAD: mandibular advancement device.[12]
- MSLT: multiple sleep latency test.[9]
- MSA: multiple system atrophy.[38]
- MT1/MT2: melatonin receptor subtypes 1 and 2.[6, 34]
- MWT: maintenance of wakefulness test.[15]
- NT1/NT2: narcolepsy type 1 / type 2.[15]
- OSA or OSAS: obstructive sleep apnea / obstructive sleep apnoea syndrome.[4, 12]
- OX1R/OX2R: orexin receptor 1 / orexin receptor 2.[3, 26]
- PD: Parkinson disease.[38]
- PLMS: periodic limb movements of sleep.[8]
- PSG: polysomnography.[1, 12]
- RBD: REM sleep behavior disorder.[7]
- RWA or RSWA: REM sleep without atonia.[19]
- RLS: restless legs syndrome.[22]
- SOREMP: sleep-onset REM period.[9]
- SWSD: shift work sleep disorder.[34]
- TEAE: treatment-emergent adverse event.[31]
- TST: total sleep time.[3]
- UPPP: uvulopalatopharyngoplasty.[12]
- vPSG: video polysomnography.[7]
- WASO: wake after sleep onset.[11]
- α2δ ligands: alpha-2-delta ligands (gabapentinoids).[21]
