Insomnia and Sleep Apnea — The Alarm That Won't Switch Off, the Airway That Closes

Two Ways Sleep Breaks Down

You wake up at three in the morning. Tasks for tomorrow cross your mind, you check the clock, and you count the hours left until you have to get up. Nights like this happen to everyone. Three or four out of ten adults report that even at this very moment, they find it difficult to fall asleep or wake up during the night. A smaller number, a little over one out of ten, experience nights like this frequently and persistently enough to be called a disease (PMID 41467350).

At the same hour in the next room, something else is happening. One person snores loudly, falls quiet, and a moment later gasps for breath before snoring again. This person fell asleep easily, but does not feel refreshed in the morning and keeps dozing off during the day (PMID 42441964, PMID 41820035).

The first person's sleep breaks down because sleep will not come. The second person's sleep breaks down because breathing is blocked while they sleep. The two breakdowns differ in their causes, how they are identified, and their treatments. When the first breakdown is frequent and long-lasting, it becomes a disease called insomnia, and the disease that represents the second breakdown is sleep apnea.

How Occasional Sleepless Nights Differ from Insomnia

European guidelines draw the line with numbers. Insomnia is a disorder in which difficulty falling or staying asleep despite adequate opportunity to sleep persists for at least three days a week and for at least three months, thereby disrupting daytime functioning. This is the criterion published in the summary of the 2023 European guidelines (PMID 42774779).

This definition has four conditions: frequency (three days a week), duration (three months), having the opportunity to sleep, and daytime impairment. People who voluntarily cut short their sleep time due to a busy schedule are filtered out by the third condition. Such short sleep is covered in another part of this series, "Sleep Loss".

If you count without the fourth condition—daytime impairment—insomnia can be counted more than it actually is. When 21,083 adults aged 40 to 99 in Tromsø, Norway, were classified using four diagnostic criteria, the percentage of people classified with insomnia ranged from 23.6% under the broadest criterion to 8.5% under the narrowest (PMID 38718598). More than half of the people classified under the two broader criteria did not report having daytime functioning impairments on three or more days a week. The researchers conclude that failing to properly include daytime symptoms can inflate the count of insomnia (PMID 38718598).

Insomnia that meets the criteria often does not pass quickly. About half of the people suffering from insomnia have the condition persist for a long time (PMID 23423416).

Reading the criteria makes you measure your own sleep against them. However, diagnosis is made through an interview. Doctors ask in detail about sleep habits, physical and mental illnesses, and medications being taken. A sleep diary, in which sleep and wake times are recorded every day, is also used alongside this (PMID 23423416, PMID 38016484). European guidelines state that wrist-worn actigraphy is not recommended for routine evaluation of insomnia (PMID 38016484).

There is also a separate test measured by sleeping overnight in a hospital. Polysomnography is a test that simultaneously records brain waves, eye movements, muscle activity, breathing, and blood oxygen levels while sleeping. European guidelines do not recommend using this test to confirm insomnia itself. They advise using it when other sleep disorders, such as sleep apnea, are suspected, or for insomnia that does not respond well to treatment (PMID 38016484). The yardstick distinguishing insomnia is duration, frequency, and daytime, rather than one night of distress.

Why It Continues — An Alarm That Won't Turn Off

It is common to lose sleep the week before a major presentation. Why this kind of event hardens into a disorder is still at the hypothesis stage, and one review explains it this way (PMID 42574939). When acute stress arrives, the brain circuits that scan for danger crank up wakefulness. In the face of danger, that is a useful response. But when stress lasts a long time, these circuits themselves change, and the brain's brakes that suppress wakefulness grow weaker. Then, a temporary state of alert hardens into constant wakefulness. Exactly how this process happens inside the brain is not yet clear (PMID 42574939).

There is a name attached to that hardened state. Hyperarousal is a state where the body and mind remain switched on even when they need to rest. Current theories view insomnia as a disorder of hyperarousal that runs 24 hours a day, night and day (PMID 41467350, PMID 42574939). In the bodies of people with insomnia, markers leaning toward hyperarousal are reported. Examples include the stress hormone cortisol, nerve signals that raise tension, changes in heart rate, and mild inflammation (PMID 41467350).

Compared to a fire alarm, an alarm sounding during acute stress is doing its job. Insomnia is closer to a state where the alarm does not turn off even after the fire is out.

There are also hands that keep pressing the alarm again. In people with insomnia, rigid beliefs about sleep, attention drawn to sleep-related cues, worry, and rumination are common (PMID 36866434). Beliefs like "If I can't sleep again today, tomorrow is ruined" are examples. These beliefs are counted among the loops of thought that keep insomnia going. As beliefs soften, there is an association where the severity of insomnia also improves (PMID 37862834). However, in some studies, sleep improved first and beliefs softened later. Which of the two comes first has not been sorted out yet (PMID 37862834). The treatments we will look at later target precisely these habits—namely, the behaviors and thoughts that keep the malfunction of sleep going (PMID 42120163).

When insomnia lasts a long time, it does not end as just a problem of sleep. Daytime function drops, and it is linked to other physical and mental illnesses as well (PMID 23423416). Follow-up studies report that persistent insomnia is linked to the appearance of new depression (PMID 12531146). Beyond simply feeling that one's sleep is short, there is insomnia where sleep is short even when measured by machines. In this kind of insomnia, observational studies show a higher risk of cardiometabolic diseases (PMID 41467350). The forces that keep insomnia going are the alarm switched on night and day, and the worries and habits that press that alarm again.

The Treatment Recommended First by Guidelines — Cognitive Behavioral Therapy for Insomnia

Cognitive behavioral therapy for insomnia is a drug-free treatment for insomnia designed to change thoughts about sleep and bedtime habits. It combines several techniques. It brings together several approaches: cognitive therapy that addresses thoughts about sleep, two techniques that change bedtime behavior, lifestyle guidance, and relaxation to ease bodily tension (PMID 26054060).

The effects are most clearly seen in the time it takes to fall off to sleep and the time spent awake in the middle of the night. Chronic insomnia patients who received this treatment took an average of 19 minutes less time to fall asleep and spent an average of 26 minutes less time awake in the middle of the night compared to a control group that did not receive the treatment (PMID 26054060). In the same analysis, the share of actual sleep time out of the total time spent lying down increased by 9.9 percentage points. The effects seemed to persist up to later time points, and no harmful outcomes were reported (PMID 26054060). However, this analysis only gathered studies that excluded insomnia with comorbid other medical conditions (PMID 26054060).

Total sleep time yields mixed results across analyses. In the preceding analysis, it increased by an average of 7.6 minutes right after treatment, but a difference of this magnitude was hard to distinguish from a chance difference and thus was not statistically distinct (PMID 26054060). In another analysis combining 61 trials, total sleep time increased by 16 to 34 minutes compared to routine care, depending on the format (PMID 35759820). This means that the outcomes most clearly reduced by this treatment are the time until falling asleep and the time awake in the middle of the night, whereas how much total sleep time increases is less clear than that.

The two techniques that change bedtime behavior are worth knowing by name. Stimulus control is a method of using the bed only for sleeping, getting out of bed if sleep does not come, and returning when feeling sleepy. Sleep restriction is a treatment that makes sleep solid by reducing the time spent lying in bed to close to the actual sleep time, with a therapist setting and adjusting the time while reviewing a sleep diary. Here, sleep becoming solid means that the time spent awake while lying down decreases. Sleep restriction is the factor that most decisively determines the success or failure of the treatment. Cognitive techniques that handle beliefs and worries about sleep add to the effectiveness (PMID 36866434).

Sleep restriction also comes with a price. While it is a treatment with clear effects, daytime side effects, especially sleepiness, can be distressing for patients. That sleepiness may be part of what is experienced and passed through during the treatment process (PMID 36003019). Therefore, sleep restriction is a treatment adjusted by a therapist who looks at both the sleep diary and daytime condition together, and patients are typically instructed to be careful with dangerous tasks like driving while they are sleepy.

How sleep restriction works has barely been uncovered yet. A leading candidate is sleep pressure. Sleep pressure is the force that makes you want to sleep, which builds up the longer you stay awake and dissipates while you sleep. An analysis examining 15 studies of generally low quality found frequent results showing that the time it took to fall asleep decreased, which suggests that sleep pressure had increased (PMID 30177248). However, those values were mostly measured at the end of treatment. They are merely the improved results at the end of treatment and do not show through what path the treatment operated (PMID 30177248). Results showing reduced hyperarousal appeared only in a few studies without control groups, and not a single study was designed to isolate the mechanism of action (PMID 30177248). The discussion on sleep pressure continues in "Sleep Pressure and the Body Clock", another part of this series.

The alarm metaphor reveals its limits here. Cognitive techniques target the hand pressing the alarm again. Whether sleep restriction, the strongest component, is turning off the alarm, building up sleep pressure, or both, has not yet been sorted out (PMID 30177248). Whether the alarm itself—that is, hyperarousal—decreases after treatment is also still rarely studied (PMID 36866434).

Guidelines place this treatment right at the front. In its 2016 guideline, the American College of Physicians recommended cognitive behavioral therapy for insomnia as the first treatment for all adults with chronic insomnia (strong recommendation, moderate-quality evidence) (PMID 27136449). The European 2023 guideline also recommends this treatment as the primary treatment for adult chronic insomnia. It applies regardless of age, includes people with comorbid other illnesses, and does not restrict the format, whether face-to-face or digital (PMID 38016484). Both the American College of Physicians and European guidelines recommend cognitive behavioral therapy for insomnia as the first treatment for chronic insomnia.

There are four ways to receive this treatment. One-on-one, group, guided internet formats, and fully automated internet formats all increased the likelihood of resolving insomnia compared to control groups (PMID 41259947). The difference lay in the completion rate. One-on-one was 83.8%, the fully automated internet format was 58.4%, and sticking with internet-based formats to the end remains a challenge (PMID 41259947).

This treatment has limitations as well. It does not work for everyone, and only a few factors that gauge who it will work better for have been consistently identified (PMID 41861511). Contrary to the recommendations, few patients are actually connected to this treatment in real clinical practice (PMID 29619651).

Sleep habit guidance, which is often recommended like a treatment, also has a name. Sleep hygiene education is teaching lifestyle habits good for sleep, such as caffeine, alcohol, exercise, bedroom environment, and a regular wake-up time. Sleep as felt by oneself improves a little after this education. However, the effect is smaller than cognitive behavioral therapy, and what role it should play in primary care has not been settled (PMID 29194467).

Sleeping Pills — The Benefits and the Price Together

Among insomnia medications, the ones with the most accumulated evidence are the benzodiazepine family and sleeping pills grouped as acting similarly to them. This family works, but the effect is modest, and safety concerns have consistently followed alongside it. Reviews in this field therefore conclude that while sleeping pills are effective drugs, they must be used while closely monitoring for side effects (PMID 23423416). Side effects from long-term use are also known. Dependence, withdrawal symptoms when stopping, rebound insomnia where sleep worsens after stopping, cognitive decline, and falls are linked to the long-term use of this family (PMID 42751933).

Guidelines place sleeping pills as a fallback when cognitive behavioral therapy is insufficient, weighing their benefits and side effects together. The 2023 European guidelines state that medication can be suggested when cognitive behavioral therapy is not sufficiently helpful. They allow various families to be used for short-term treatment. Depending on the drug family, using them longer or starting long-term use while weighing pros and cons is left for some cases (PMID 38016484). The American College of Physicians recommends shared decision-making for individuals who do not improve with cognitive behavioral therapy alone. This approach involves the doctor and patient discussing and deciding together on the benefits, harms, and costs of short-term drug treatment (weak recommendation, low-quality evidence) (PMID 27136449).

Regarding whether to start both treatments together from the beginning, the American Academy of Sleep Medicine's 2026 guidelines give different answers depending on the comparator (PMID 41975142). Compared to using sleeping pills alone, the guidelines suggest using cognitive behavioral therapy and sleeping pills together. Compared to doing cognitive behavioral therapy alone, the guidelines suggest not adding sleeping pills, meaning doing cognitive behavioral therapy alone. Both suggestions are conditional recommendations, and the certainty of the evidence is low (PMID 41975142). A conditional recommendation is one left for the doctor to choose by weighing the patient's values and preferences (PMID 41975142). The same guidelines add that for patients who prioritize quickly increasing the time spent asleep in the early stages of treatment, choosing to use them together can be reasonable (PMID 41975142).

When looking at individual drugs, the judgment becomes even more cautious. The American Academy of Sleep Medicine's 2017 medication guidelines issued separate judgments for each drug, attaching a "weak recommendation" to both drugs suggested for use and drugs suggested not to be used (PMID 27998379). The guidelines clarify that a weak recommendation for a suggested drug does not mean it is ineffective. It means the certainty of the evidence was rated low, for three reasons: each drug has few trials, results are inconsistent, and most trials are funded by pharmaceutical companies, carrying a risk of publication bias (PMID 27998379). Publication bias is a phenomenon where studies with favorable results are published more readily, making the overall evidence appear better than it actually is.

The 2023 European guidelines use a different grading framework, making direct comparison difficult. These guidelines assigned grade A for short-term use of various drug families, and grade B—one step lower—for initiating longer-term use (PMID 38016484).

There are also drugs that are not recommended. The European guidelines do not recommend antihistamine-class drugs or herbal preparations, and the American Academy of Sleep Medicine guidelines also do not recommend diphenhydramine, an antihistamine ingredient, or valerian, an herb (PMID 27998379, PMID 38016484). Melatonin is an internal body signal announcing nighttime, and taking it as a pill is not recommended by the American Academy of Sleep Medicine's 2017 guidelines (PMID 27998379). The European guidelines do not recommend regular, fast-dissolving melatonin. They state that only slow-release formulations can be used in a limited manner for a set duration in older adults (PMID 38016484).

Judgments from guidelines can also diverge for the same drug. A drug called ramelteon was weakly suggested for insomnia with difficulty falling asleep by the American Academy of Sleep Medicine's 2017 guidelines, whereas the 2023 European guidelines do not recommend it (PMID 27998379, PMID 38016484).

Newly introduced drug families also come with a price. Orexin is a brain signal that keeps people awake, and sleeping pills that block the receptors where this signal attaches have newly emerged. These sleeping pills had a 2.15 times higher risk of daytime drowsiness than a dummy pill with no active ingredient, known as a placebo. The risk of sleep paralysis—a temporary inability to move the body around the time of falling asleep or waking up—was 3.40 times higher (PMID 37950346). Pooling trials that used this family for 6 months and 12 months, self-reported improvements in sleep persisted. Side effects were similar to the placebo at 6 months but more frequent at 12 months, while the proportion of discontinuations due to side effects did not clearly differ from the placebo (PMID 42595319). The researchers note that overall safety is acceptable, while adding that longer trials are needed (PMID 42595319).

A gap exists between guidelines and clinical practice. A qualitative study interviewing 11 experienced general practitioners in Norway illustrates this gap (PMID 39029944). The doctors knew that prescribing sleeping pills daily to patients over 70 goes against the guidelines. At the same time, they viewed that prescription as acceptable for certain patients who had few realistic alternatives (PMID 39029944). The researchers conclude that the goal of reducing sleeping pill prescriptions for the elderly to zero may be neither prudent nor realistic (PMID 39029944).

Tapering off long-term sleeping pills is done by slowly reducing them through a personalized plan established together with the prescribing doctor (PMID 42751933). An analysis combining 13 randomized trials concludes that there is no clear evidence that adding cognitive behavioral therapy increases the rate of completely stopping sleeping pills (PMID 42751933). The cessation rate and the tapering process are different issues. The same analysis suggests that cognitive behavioral therapy can be helpful in lowering doses and enduring insomnia while tapering slowly (PMID 42751933). Sleeping pills are drugs that work, and their price is also known.

Obstructive Sleep Apnea — The Airway That Closes During Sleep

Let us return to the person snoring at the beginning. The breathing pauses and gasping between snores, along with daytime sleepiness, point to one condition. Obstructive sleep apnea is a condition where the airway in the back of the throat repeatedly narrows or closes during sleep, causing breathing to drop sharply or stop.

Common symptoms include loud snoring, waking up during the night, and daytime sleepiness (PMID 42441964). Breathing pauses observed by a bedpartner, waking up choking or gasping at night, morning headaches and dry mouth, and unrefreshing sleep despite sleeping are also listed as common symptoms (PMID 41820035). Women often present with symptoms that differ from the typical pattern seen in men, making the condition easy to diagnose late (PMID 41234172).

Snoring is merely a common sign of sleep apnea; not everyone who snores has sleep apnea. The 2025 sleep apnea guidelines of the Chinese Thoracic Society also refer to "simple snoring"—snoring without breathing pauses—separately from sleep apnea (PMID 41820035). Conversely, some people have sleep apnea without feeling sleepy during the day. Even in such cases, sleep apnea is linked to a high cardiovascular risk (PMID 42349065).

The severity of the condition is mainly measured by the number of times breathing is blocked. The apnea-hypopnea index is the number of times breathing stops or drops significantly per hour of sleep. Five or more times per hour is counted as mild or worse, and 15 or more times as moderate or worse (PMID 31300334).

Counted by this criterion, sleep apnea is very common. An estimated 936 million adults aged 30 to 69 worldwide are estimated to have sleep apnea. Among them, about 425 million have moderate or worse disease (PMID 31300334). However, this number is an estimate. Test data from 16 countries were applied to other countries, and the presence of symptoms was not analyzed separately. Funding for the study was provided by ResMed, a company that manufactures sleep-breathing treatment devices (PMID 31300334).

A questionnaire is not a diagnosis. When a widely known screening questionnaire is used for people with cardiovascular risk factors, it catches 89.1% of people with sleep apnea. Therefore, the researchers conclude that it is effective as a filtering tool (PMID 33664122). However, only 32.3% of people without sleep apnea went undetected by the questionnaire (PMID 33664122). This means that two out of three people who do not have sleep apnea also test positive on the questionnaire.

Diagnosis is made through a test that actually measures breathing during sleep. The 2017 diagnostic guidelines of the American Academy of Sleep Medicine designate polysomnography as the standard diagnostic test. They recommend that diagnosis should not be made based solely on questionnaires or prediction tools without polysomnography or a home sleep apnea test (strong recommendation) (PMID 28162150). A home test is an examination that measures only a few variables at home, such as breathing and blood oxygen. The guidelines state that home tests can also be used for people who are suspected of having moderate or worse disease without mixed other conditions. If the home test is negative or inconclusive, polysomnography is recommended (strong recommendation) (PMID 28162150).

The 2025 guidelines of the Chinese Thoracic Society also state that sleep apnea should not be ruled out using home tests alone. They note that validated consumer sleep trackers and wearables can be used as aids to prompt high-risk groups to seek medical consultation, but cannot replace hospital tests (PMID 41820035).

Daytime sleepiness brings safety concerns. The Chinese guidelines examine the risks of traffic accidents and occupational accidents for people with sleep apnea separately. They also recommend including individuals whose risk of accidents while driving or at work may increase due to sleep apnea as targets for screening (PMID 41820035).

The representative treatment device that reduces that daytime sleepiness is the positive airway pressure device. A positive airway pressure device is a machine that blows air with a slightly strong pressure through a mask worn over the nose or mouth, propping the airway open so it does not close during sleep. Positive airway pressure therapy relieves breathing blockages to improve daytime sleepiness, quality of life, blood pressure, and cognitive function (PMID 30617618).

Guidelines differ on what they prioritize when deciding who receives a positive airway pressure device. American guidelines look at symptoms first, whereas Chinese guidelines look at the index first. The 2019 positive airway pressure guidelines of the American Academy of Sleep Medicine require that the diagnosis be confirmed first by objective sleep testing before starting positive airway pressure (PMID 30736887). Among diagnosed sleep apnea cases, they strongly recommend using positive airway pressure if the patient is excessively sleepy during the day. They conditionally suggest it if sleep-related quality of life is impaired or if high blood pressure is present (PMID 30736887). The Chinese guidelines recommend positive airway pressure as the first-line treatment for moderate or worse sleep apnea with an index of 15 or higher. They state that it can be considered even for mild cases if daytime sleepiness is pronounced or if conditions such as cardiovascular disease are present (PMID 41820035).

The challenge is consistent use. Although positive airway pressure has high efficacy, the extent to which people actually use it consistently is often inadequate (PMID 30617618). The 2019 guidelines of the American Academy of Sleep Medicine strongly recommend providing education when initiating positive airway pressure. Adding behavioral therapy, problem-solving support, or telemonitoring early on is conditionally suggested (PMID 30736887).

Options other than positive airway pressure also exist. The 2021 guidelines of the European Respiratory Society cover non-positive airway pressure treatments separately. The list includes custom oral appliances, stimulation of the nerve that moves the tongue, throat and mouth muscle training, positional therapy, surgery, and medications (PMID 34853097). The Chinese guidelines recommend oral appliances for simple snoring, mild to moderate sleep apnea, and individuals who cannot tolerate positive airway pressure (PMID 41820035). Lifestyle adjustments such as weight management, abstaining from alcohol, quitting smoking, and regular exercise are recommended for all patients. Positional therapy is recommended for individuals whose condition worsens depending on sleeping on their back (PMID 41820035).

The cardiovascular side is still a half-open question. A systematic review is an analysis that collects studies on a single topic exhaustively using established methods and re-examines them. In an analysis pooling 38 such reviews, positive airway pressure lowered systolic blood pressure by an average of 4.8 mmHg and diastolic blood pressure by 3.0 mmHg (PMID 42654353). Systolic blood pressure is the blood pressure when the heart squeezes out blood, and diastolic blood pressure is the blood pressure while the heart rests. Cardiac function indicators also improved, but the certainty of the evidence was low to moderate (PMID 42654353).

Although positive airway pressure improves daytime sleepiness and quality of life and lowers blood pressure slightly, it has not yet been proven to reduce major cardiovascular events and cardiovascular death (PMID 30617618, PMID 42654353). "Not proven" is different from confirming that it cannot reduce them. The same analysis concludes that longer-term, high-quality randomized trials are needed (PMID 42654353).

When Two Breakdowns Overlap in One Person

Insomnia and sleep apnea often come together. 38% of people with sleep apnea have insomnia, and 35% of people with insomnia have coexisting sleep apnea with an apnea-hypopnea index of 5 or higher (PMID 30844624). Various studies have reported that people with both conditions overlapping experience greater daytime disruption and a lower quality of life than those with just one side (PMID 30844624).

Let us imagine someone who visits a clinic because they cannot sleep, mentioning snoring alongside pauses in breathing witnessed by a partner. These two features are classic symptoms of sleep apnea (PMID 41820035). This person falls under the cases where the European insomnia guidelines dictate using polysomnography, meaning when another sleep disorder is suspected (PMID 38016484). The 2017 diagnostic guidelines of the American Academy of Sleep Medicine also recommend diagnosing people with severe insomnia through polysomnography rather than a home-based portable test (PMID 28162150).

Even when both conditions are confirmed, cognitive behavioral therapy for insomnia still works. In people with overlapping conditions, this therapy substantially reduced insomnia severity. It proved effective both in people whose sleep apnea had not yet been treated and in those already undergoing treatment (PMID 36872072).

For the sleeping pills from the previous section, one more condition is attached here. Among sedative and sleeping drugs, some can trigger or worsen sleep apnea. Chinese guidelines recommend using such medications with caution or avoiding them (PMID 41820035). When the two conditions overlap, the benzodiazepine class is not recommended. Other select sleeping pills are permitted for short-term use under close monitoring or when used alongside positive airway pressure therapy (PMID 41820035). When two breakdowns overlap in one person's sleep, one must even weigh the impact that a method fixing one side has on the other.

Other Sleep Disorders — Names and One-Liners

Restless legs syndrome is a condition where an urge to move the legs washes over you along with an uncomfortable sensation in the legs, which grows worse when you stay still and in the evening and at night, but eases when you move. It has become known that older, first-line dopamine-class drugs can paradoxically worsen the symptoms when used for a long time. Therefore, gabapentin-class drugs are now placed as the first line, and the role of iron therapy has also expanded (PMID 25979181, PMID 42203073).

Narcolepsy is a condition in which hard-to-resist sleepiness repeats during the day, and sudden loss of muscle strength while remaining fully conscious can also accompany it, often triggered by strong emotions like laughter. Type 1 narcolepsy is caused by the loss of nerve cells in the brain that make orexin. There is no cure for the disease yet, but there are treatments to manage the symptoms (PMID 41097925).

REM sleep is a sleep state where the eyeballs move rapidly beneath closed eyelids and most of the body's muscles go limp so they do not move, and people experience many vivid dreams. Because of this, even if you run or fight in your dream, your body stays still in bed. REM sleep behavior disorder is a condition where the muscles that should be limp during REM sleep fail to relax, causing the person to act out their dreams with their actual body. Both the sleeping person and the person sleeping next to them can get hurt (PMID 33410930).

When REM sleep behavior disorder occurs by itself without other diseases, it is common in older men, and its link to diseases such as Parkinson's disease is known (PMID 38657360). Such cases are viewed as a prodromal stage of those diseases, and research continues to find markers that gauge the risk of progression (PMID 36789541). It can also arise due to other conditions besides medication or neurodegeneration (PMID 38657360). Diagnosis is made through a clinical interview and polysomnography (PMID 36789541).

The evidence base for treatment is still thin. Two drugs commonly used as first-line treatments are clonazepam and melatonin. While observational reports showed not a few patients improving, three small placebo-controlled trials showed no superiority over placebo. Therefore, the authors write that larger trials are urgently needed (PMID 33410930). Making the sleeping environment safe to prevent injury is commonly cited as the primer of management.

Sleep disorders caused by a mismatch in the internal body clock are covered in "Sleep Pressure and the Body Clock".

Where to Look Further

• Other parts of this series: What happens in the brain while we sleep is in "Sleep Stages and Sleep Cycles", what calls and wakes us to sleep is in "Sleep Pressure and the Body Clock", and what happens when sleep falls short is in "Sleep Loss".
• What the blood pressure lowered by a CPAP machine measures is in "What Blood Pressure Measures".
• The heart rhythm disease often mentioned alongside sleep apnea is in "What Atrial Fibrillation Is".

Open questions also remain. Research continues on whether cognitive behavioral therapy for insomnia calms hyperarousal itself, and whether CPAP machines reduce major cardiovascular events.

Source Papers

• "The European 2023 Guideline on diagnosing and treating insomnia disorder: A Plain Language Summary of Publication." (2026) — PMID 42774779 — Summary of the 2023 European guidelines: Insomnia = difficulty falling or staying asleep for 3 days or more per week for 3 months or more despite adequate opportunity + daytime impairment.
• "The European Insomnia Guideline: An update on the diagnosis and treatment of insomnia 2023." (2023) — PMID 38016484 — Diagnosed via interviews and sleep diaries, daily actigraphy assessment not recommended, polysomnography reserved for suspected other sleep disorders or treatment resistance, cognitive behavioral therapy as first-line (A), pharmacotherapy if insufficient, short-term use of multiple classes (A) or initiating long-term (B), antihistamines, immediate-release melatonin, ramelteon, and herbal products not recommended.
• "Management of Chronic Insomnia Disorder in Adults: A Clinical Practice Guideline From the American College of Physicians." (2016) — PMID 27136449 — Cognitive behavioral therapy as the initial treatment for all adults with chronic insomnia (strong recommendation), short-term pharmacotherapy via shared decision-making if it fails (weak recommendation).
• "Combination treatment for chronic insomnia disorder in adults: an American Academy of Sleep Medicine clinical practice guideline." (2026) — PMID 41975142 — Suggests combination treatment over medication alone, suggests against combination treatment over cognitive behavioral therapy alone (both conditional and low certainty), choosing combination treatment is reasonable for patients who prioritize initial sleep duration.
• "Clinical Practice Guideline for the Pharmacologic Treatment of Chronic Insomnia in Adults: An American Academy of Sleep Medicine Clinical Practice Guideline." (2017) — PMID 27998379 — All individual drug recommendations (suggested or not suggested) are weak recommendations, weak recommendation ≠ no effect, downgrades expected due to number of trials, heterogeneity, and publication bias, ramelteon suggested, diphenhydramine, melatonin, and valerian not suggested.
• "Cognitive Behavioral Therapy for Chronic Insomnia: A Systematic Review and Meta-analysis." (2015) — PMID 26054060 — 20 studies involving 1,162 participants, improvements of 19 minutes in sleep onset and 26 minutes in wake after sleep onset, total sleep time 7.6 minutes (non-significant), sleep efficiency 9.9%, sustained, no harmful outcomes reported, comorbid conditions excluded.
• "Comparative efficacy and acceptability of cognitive behavioral therapy delivery formats for insomnia in adults: A systematic review and network meta-analysis." (2022) — PMID 35759820 — 61 studies involving 11,571 people, various delivery methods increased total sleep time by 16 to 34 minutes and decreased sleep onset and wake after sleep onset compared to routine care, maintained through short-term follow-up.
• "Remission, treatment response, and treatment adherence across the delivery methods of cognitive behavioral therapy for insomnia..." (2025) — PMID 41259947 — Increased remission across all delivery methods, completion rates 83.8% for one-on-one and 58.4% for fully automated internet-based.
• "Armodafinil to reduce the sleepiness related side-effects of sleep restriction therapy being used to treat insomnia disorder: An open label clinical trial pilot study compared with historical controls." (2023) — PMID 36003019 — Background sentence only: Sleep restriction therapy is effective, but daytime side effects, especially sleepiness, can be distressing and/or a necessary part of the treatment process (drug trial results are not used).
• "How does sleep restriction therapy for insomnia work? A systematic review of mechanistic evidence and the introduction of the Triple-R model." (2018) — PMID 30177248 — Mechanisms largely unknown, study quality low, reduction in sleep onset latency is usually measured at the end of treatment so it is an outcome rather than a mechanism, decreased arousal supported only by a few non-controlled studies, no mediation verification studies.
• "Mechanisms of cognitive behavioural therapy for insomnia." (2023) — PMID 36866434 — Dysfunctional beliefs, selective attention, worry, and rumination in insomnia, sleep restriction is the strongest determinant of success or failure, studies tracking post-treatment changes in hyperarousal are rare.
• "Challenging beliefs for quality sleep: A systematic review of maladaptive sleep beliefs and treatment outcomes following cognitive behavioral therapy for insomnia." (2023) — PMID 37862834 — Reduction in beliefs linked to severity improvement, sleep improvement comes first in some cases, direction undetermined.
• "Nonpharmacologic Management of Insomnia Disorder in Primary Care." (2026) — PMID 42120163 — Cognitive behavioral therapy addresses the behavioral and cognitive patterns that maintain sleep disorders.
• "Predictors and moderators of treatment outcomes from cognitive behavioural interventions for insomnia in adults: A systematic review." (2026) — PMID 41861511 — Cognitive behavioral therapy does not work for everyone, most predictor factors are rarely studied and rarely significant.
• "Increasing access to and utilization of cognitive behavioral therapy for insomnia (CBT-I): a narrative review." (2018) — PMID 29619651 — Patients are rarely referred for this treatment despite recommendations.
• "Sleep hygiene education as a treatment of insomnia: a systematic review and meta-analysis." (2018) — PMID 29194467 — Sleep hygiene education yields small to medium improvements, less effective than cognitive behavioral therapy, primary care role cannot be concluded.
• "Mechanisms Linking Insomnia and Cardiometabolic Disease Risk." (2026) — PMID 41467350 — Insomnia symptoms in 30% to 40%, 24-hour hyperarousal (cortisol, sympathetic activity, heart rate variability, inflammation), cardiometabolic risk when accompanied by objective short sleep duration.
• "When stress becomes wakefulness: Stress-arousal circuitry and the state control of insomnia." (2026) — PMID 42574939 — Convergence on hyperarousal disorder, acute stress promotes vigilance, suggestion (hypothesis) that chronic stress weakens braking mechanisms, circuit mechanisms unclear.
• "Insomnia." (2013) — PMID 23423416 — Prevalence 10% to 20%, about half chronic, causes converge on hyperarousal, diagnosed via interviews and sleep diaries, medications are effective but safety concerns outweigh their modest benefits, monitoring for side effects.
• "Epidemiology of insomnia: what we know and what we still need to learn." (2002) — PMID 12531146 — Persistence of insomnia is linked to the emergence of new depressive episodes (longitudinal study).
• "Prevalence of insomnia in a general adult population cohort using different diagnostic criteria: The seventh survey of the Tromsø study 2015-2016." (2024) — PMID 38718598 — 21,083 people, 23.6% to 8.5% depending on criteria, more than half under broad criteria reported no daytime impairment, overestimation when daytime symptoms are omitted.
• "Cognitive behavioral therapy for insomnia-assisted discontinuation or reduction of benzodiazepine receptor agonists and Z-drugs in chronic insomnia: A systematic review and meta-analysis." (2026) — PMID 42751933 — Long-term use linked to dependence, withdrawal, rebound insomnia, cognitive decline, and falls, strong evidence that combining cognitive behavioral therapy does not increase complete discontinuation rates, may help during gradual tapering.
• "Clinical safety and narcolepsy-like symptoms of dual orexin receptor antagonists in patients with insomnia: a systematic review and meta-analysis." (2024) — PMID 37950346 — Daytime sleepiness relative risk 2.15 vs. placebo, sleep paralysis relative risk 3.40.
• "Long-term use of dual orexin receptor antagonists for the treatment of insomnia: a systematic review and meta-analysis." (2026) — PMID 42595319 — Subjective efficacy maintained at 6 and 12 months, side effects similar to placebo at 6 months but increased at 12 months, no difference in discontinuation rates due to side effects, overall safety acceptable, long-term trials needed.
• "GPs' reflections on prescribing addictive hypnotics to older people: a qualitative study." (2024) — PMID 39029944 — Interviews with 11 Norwegian general practitioners, prescribing to a few patients while knowing it contradicts guidelines, a "zero target" may be neither prudent nor realistic.
• "Clinical Practice Guideline for Diagnostic Testing for Adult Obstructive Sleep Apnea: An American Academy of Sleep Medicine Clinical Practice Guideline." (2017) — PMID 28162150 — Polysomnography is the standard diagnostic test, diagnosis using questionnaires and prediction tools alone is prohibited (strong), home sleep apnea testing permitted for uncomplicated patients with suspected moderate or greater severity (strong), polysomnography if home test is negative or uncertain (strong), polysomnography for severe insomnia cases (strong).
• "Treatment of Adult Obstructive Sleep Apnea with Positive Airway Pressure: An American Academy of Sleep Medicine Clinical Practice Guideline." (2019) — PMID 30736887 — Initiated after diagnosis via objective testing, positive airway pressure when excessive sleepiness is present (strong), when sleep-related quality of life is impaired or hypertension is present (conditional), education at initiation (strong), initial behavioral interventions, problem-solving, and remote monitoring (conditional).
• "European Respiratory Society guideline on non-CPAP therapies for obstructive sleep apnoea." (2021) — PMID 34853097 — Guidelines for treatments other than positive airway pressure: bariatric surgery, customized titratable mandibular advancement devices, hypoglossal nerve stimulation, myofunctional therapy, maxillomandibular advancement surgery, carbonic anhydrase inhibitors, positional therapy.
• "[Guidelines for the diagnosis and treatment of obstructive sleep apnea in adults (2025)]." (2026) — PMID 41820035 — Chinese Thoracic Society: Symptom and risk features, distinguishing simple snoring, diagnosis using questionnaires and consumer devices prohibited, polysomnography criteria and home tests cannot rule it out, monitoring driving and occupational accident risks, positive airway pressure as first-line (AHI≥15), oral appliances, lifestyle adjustments, positional therapy, caution with sedative and sleep medications, conditions for medication when insomnia co-occurs.
• "Obstructive Sleep Apnea." (2026) — PMID 42441964 — Common yet frequently undiagnosed, loud snoring, nocturnal arousals, daytime sleepiness, treatment improves symptoms and slightly reduces blood pressure.
• "Estimation of the global prevalence and burden of obstructive sleep apnoea: a literature-based analysis." (2019) — PMID 31300334 — 936 million aged 30 to 69 (AHI≥5) and 425 million (AHI≥15), extrapolated from data across 16 countries, symptoms not analyzed, ResMed funding.
• "[Sleep apnea in women : prevalence, symptoms, phenotypes, and treatment]." (2025) — PMID 41234172 — Women present with atypical patterns leading to underdiagnosis and delays.
• "Does treatment of nonsleepy OSA with CPAP therapy change CVD risk? A systematic review." (2026) — PMID 42349065 — Sleep apnea without daytime sleepiness is also linked to increased cardiovascular risk.
• "Validation of the STOP-Bang questionnaire as a screening tool for obstructive sleep apnoea in patients with cardiovascular risk factors: a systematic review and meta-analysis." (2021) — PMID 33664122 — Sensitivity 89.1% and specificity 32.3% for AHI≥5.
• "Predictors of Continuous Positive Airway Pressure Adherence in Patients with Obstructive Sleep Apnea." (2019) — PMID 30617618 — Positive airway pressure as first-line, improves daytime sleepiness, quality of life, blood pressure, and cognition, adherence frequently insufficient, improved by support, behavioral therapy, and telemanagement.
• "Effects of Continuous Positive Airway Pressure on Surrogate, Intermediate, and Functional Cardiovascular Outcomes in Obstructive Sleep Apnea: An Umbrella Review..." (2026) — PMID 42654353 — 38 studies, systolic -4.8 and diastolic -3.0 mmHg, low to moderate certainty, insufficient proof of reduction in major adverse cardiovascular events and mortality.
• "Worldwide and regional prevalence rates of co-occurrence of insomnia and insomnia symptoms with obstructive sleep apnea: A systematic review and meta-analysis." (2019) — PMID 30844624 — 38% insomnia among sleep apnea patients, 35% sleep apnea (AHI≥5) among insomnia patients, co-occurrence worsens daytime impairment and quality of life.
• "The effect of cognitive behavioural therapy for insomnia in people with comorbid insomnia and sleep apnoea: A systematic review and meta-analysis." (2023) — PMID 36872072 — Cognitive behavioral therapy substantially improves insomnia severity in comorbid patients, both during untreated and treated sleep apnea.
• "Restless legs syndrome: clinical presentation diagnosis and treatment." (2015) — PMID 25979181 — Alpha-2-delta drugs as first-line due to long-term issues with dopamine agonists (such as augmentation), intravenous iron.
• "An Updated Algorithm for the Management of Restless Legs Syndrome." (2026) — PMID 42203073 — New indications for oral and intravenous iron, gabapentinoids as first-line, risks of dopamine agonists.
• "[Pathophysiology of Narcolepsy]." (2025) — PMID 41097925 — Daytime sleepiness, cataplexy, sleep paralysis, hypnagogic hallucinations, and nocturnal sleep fragmentation, type 1 involves loss of orexin neurons, no curative treatment.
• "A critical review of the pharmacological treatment of REM sleep behavior disorder in adults..." (2022) — PMID 33410930 — Dream enactment, self or partner injuries, multiple reports of observational improvement with two first-line drugs, no superiority over placebo in three small randomized controlled trials.
• "Secondary RBD: Not just neurodegeneration." (2024) — PMID 38657360 — REM sleep without atonia + dream enactment, isolated form linked to older men and Parkinson's disease, secondary to medications, substances, or other conditions.
• "Rapid eye movement sleep behavior disorder: a narrative review from a technological perspective." (2023) — PMID 36789541 — Isolated form is a prodromal stage of alpha-synucleinopathy, studies on conversion risk markers, diagnosis via self-report and polysomnography.