Somnolence (alternatively sleepiness or drowsiness) is a state of strong desire for

sleep Sleep is a sedentary state of mind and body. It is characterized by altered consciousness, relatively inhibited Perception, sensory activity, reduced muscle activity and reduced interactions with surroundings. It is distinguished from wakefuln ...

, or sleeping for unusually long periods (compare

hypersomnia Hypersomnia is a neurological disorder of excessive time spent sleeping or excessive sleepiness. It can have many possible causes (such as seasonal affective disorder) and can cause distress and problems with functioning. In the fifth edition ...

). It has distinct meanings and causes. It can refer to the usual state preceding falling asleep, the condition of being in a drowsy state due to circadian rhythm disorders, or a symptom of other health problems. It can be accompanied by

lethargy Lethargy is a state of tiredness, sleepiness, weariness, fatigue, sluggishness or lack of energy. It can be accompanied by depression, decreased motivation, or apathy. Lethargy can be a normal response to inadequate sleep, overexertion, overwo ...

, weakness and lack of mental agility. Somnolence is often viewed as a symptom rather than a disorder by itself. However, the concept of somnolence recurring at certain times for certain reasons constitutes various disorders, such as

excessive daytime sleepiness Excessive daytime sleepiness (EDS) is characterized by persistent sleepiness and often a general lack of energy, even during the day after apparently adequate or even prolonged nighttime sleep. EDS can be considered as a broad condition encompass ...

, shift work sleep disorder, and others; and there are medical codes for somnolence as viewed as a disorder. Sleepiness can be dangerous when performing tasks that require constant concentration, such as driving a vehicle. When a person is sufficiently fatigued,

microsleep A microsleep is a sudden temporary episode of sleep or drowsiness which may last for a few seconds where an individual fails to respond to some arbitrary sensory input and becomes unconscious.International Classification of Sleep Disorders, , pa ...

s may be experienced. In individuals deprived of sleep, somnolence may spontaneously dissipate for short periods of time; this phenomenon is the

second wind Second wind is a phenomenon in distance running, such as marathons or road running (as well as other sports), whereby an athlete who is out of breath and too tired to continue suddenly finds the strength to press on at top performance with less ex ...

, and results from the normal cycling of the circadian rhythm interfering with the processes the body carries out to prepare itself to rest. The word "somnolence" is derived from the

Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...

"somnus" meaning "sleep".

Causes

Circadian rhythm disorders

Circadian rhythm ("biological clock") disorders are a common cause of drowsiness as are a number of other conditions such as sleep apnea, insomnia and narcolepsy. The body clock disorders are classified as extrinsic (externally caused) or intrinsic. The former type is, for example, shift work sleep disorder, which affects people who work nights or rotating shifts. The intrinsic types include: * Advanced sleep phase disorder (ASPD) – A condition in which patients feel very sleepy and go to bed early in the evening and wake up very early in the morning * Delayed sleep phase disorder (DSPD) – Faulty timing of sleep, peak period of alertness, the core body temperature rhythm, hormonal and other daily cycles such that they occur a number of hours late compared to the norm, often misdiagnosed as insomnia * Non-24-hour sleep–wake disorder – A faulty body clock and sleep-wake cycle that usually is longer than (rarely shorter than) the normal 24-hour period causing complaints of insomnia and excessive sleepiness * Irregular sleep–wake rhythm – Numerous naps throughout the 24-hour period, no main nighttime sleep episode and irregularity from day to day

Physical illness

Sleepiness can also be a response to infection. Such somnolence is one of several sickness behaviors or reactions to infection that some theorize evolved to promote recovery by conserving energy while the body fights the infection using fever and other means. Other causes include: *

Anxiety Anxiety is an emotion which is characterized by an unpleasant state of inner turmoil and includes feelings of dread over anticipated events. Anxiety is different than fear in that the former is defined as the anticipation of a future threat wh ...

Brain tumor A brain tumor occurs when abnormal cells form within the brain. There are two main types of tumors: malignant tumors and benign (non-cancerous) tumors. These can be further classified as primary tumors, which start within the brain, and seco ...

* Chronic pains * Concussion – a mild traumatic brain injury *

Diabetes Diabetes, also known as diabetes mellitus, is a group of metabolic disorders characterized by a high blood sugar level ( hyperglycemia) over a prolonged period of time. Symptoms often include frequent urination, increased thirst and increased ...

* Fibromyalgia * Head injury * Hypercalcemia – too much calcium in the blood * Hypermagnesemia * Hyponatremia – low blood sodium * Hypothyroidism – the body doesn't produce enough hormones that control how cells use energy * Meningitis *

Mood disorder A mood disorder, also known as an affective disorder, is any of a group of conditions of mental and behavioral disorder where a disturbance in the person's mood is the main underlying feature. The classification is in the '' Diagnostic and St ...

s – depression * Multiple sclerosis * Narcolepsy – disorder of the nervous system * Skull fractures * Sleeping sickness – caused by a specific parasite * Stress

Medicine

* Analgesics – mostly prescribed or illicit opiates such as OxyContin or heroin * Anticonvulsants /

antiepileptic Anticonvulsants (also known as antiepileptic drugs or recently as antiseizure drugs) are a diverse group of pharmacological agents used in the treatment of epileptic seizures. Anticonvulsants are also increasingly being used in the treatment of b ...

s – such as phenytoin (Dilantin), carbamazepine (Tegretol),

Lyrica Pregabalin, sold under the brand name Lyrica among others, is an anticonvulsant, analgesic and anxiolytic medication used to treat epilepsy, neuropathic pain, fibromyalgia, restless leg syndrome, opioid withdrawal and generalized anxiety di ...

(Pregabalin) and Gabapentin * Antidepressants – for instance, sedating tricyclic antidepressants and

mirtazapine Mirtazapine, sold under the brand name Remeron amongst others, is an atypical antidepressant, and as such is used primarily to treat depression. Its effects may take up to four weeks, but can also manifest as early as one to two weeks. It is o ...

. Somnolence is less common with SSRIs and SNRIs as well as MAOIs. * Antihistamines – for instance,

diphenhydramine Diphenhydramine (DPH) is an antihistamine and sedative mainly used to treat allergies, insomnia, and symptoms of the common cold. It is also less commonly used for tremor in parkinsonism, and nausea. It is taken by mouth, injected into ...

(

Benadryl Benadryl is a brand of various antihistamine medications used to stop allergies, whose content varies in different countries, but which includes some combination of diphenhydramine, acrivastine, and/or cetirizine. It is sold by Johnson & Johnso ...

Nytol Diphenhydramine (DPH) is an antihistamine and sedative mainly used to treat allergies, insomnia, and symptoms of the common cold. It is also less commonly used for tremor in parkinsonism, and nausea. It is taken by mouth, injected into a ...

) and doxylamine (Unisom-2) *

Antipsychotics Antipsychotics, also known as neuroleptics, are a class of psychotropic medication primarily used to manage psychosis (including delusions, hallucinations, paranoia or disordered thought), principally in schizophrenia but also in a range of ...

– for example, Lurasidone (Latuda), thioridazine, quetiapine (Seroquel), olanzapine (Zyprexa), risperidone and

ziprasidone Ziprasidone, sold under the brand name Geodon among others, is an atypical antipsychotic used to treat schizophrenia and bipolar disorder. It may be used by mouth and by injection into a muscle (IM). The IM form may be used for acute agitati ...

(

Geodon Ziprasidone, sold under the brand name Geodon among others, is an atypical antipsychotic used to treat schizophrenia and bipolar disorder. It may be used by mouth and by injection into a muscle (IM). The IM form may be used for acute agitation ...

) but not haloperidol *

Dopamine agonists A dopamine agonist (DA) is a compound that activates dopamine receptors. There are two families of dopamine receptors, D2-like and D1-like, and they are all G protein-coupled receptors. D1- and D5-receptors belong to the D1-like family and the ...

used in the treatment of

Parkinson's disease Parkinson's disease (PD), or simply Parkinson's, is a long-term degenerative disorder of the central nervous system that mainly affects the motor system. The symptoms usually emerge slowly, and as the disease worsens, non-motor symptoms beco ...

– e.g. pergolide, ropinirole and pramipexole. * HIV medications – such as efavirenz * Hypertension medications – such as

amlodipine Amlodipine, sold under the brand name Norvasc among others, is a calcium channel blocker medication used to treat high blood pressure and coronary artery disease. It is taken by mouth. Common side effects include swelling, feeling tired, ...

* Hypnotics, or soporific drugs, commonly known as sleeping pills. *

Tranquilizers A tranquilizer is a drug that is designed for the treatment of anxiety, fear, tension, agitation, and disturbances of the mind, specifically to reduce states of anxiety and tension. Etymology Tranquilizer, as a term, was first used by F.F. Yon ...

– such as

zopiclone Zopiclone, sold under the brand name Imovane among others, is a nonbenzodiazepine used to treat difficulty sleeping. Zopiclone is molecularly distinct from benzodiazepine drugs and is classed as a cyclopyrrolone. However, zopiclone increases th ...

(Zimovane), or the benzodiazepines such as diazepam (Valium) or nitrazepam (Mogadon) and the barbiturates, such as amobarbital (Amytal) or secobarbital (Seconal) * Other agents impacting the

central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all p ...

in sufficient or toxic doses

Assessment

Quantifying sleepiness requires a careful assessment. The diagnosis depends on two factors, namely chronicity and reversibility. Chronicity signifies that the patient, unlike healthy people, experiences persistent sleepiness, which does not pass. Reversibility stands for the fact that even if the individual goes to sleep, the sleepiness may not be completely gone after waking up. The problem with the assessment is that patients may only report the consequences of sleepiness: loss of energy, fatigue, weariness, difficulty remembering or concentrating, etc. It is crucial to aim for objective measures to quantify the sleepiness. A good measurement tool is the ''multiple sleep latency test'' (MSLT). It assesses the sleep onset latency during the course of one day—often from 8:00 to 16:00. An average sleep onset latency of less than 5 minutes is an indication of pathological sleepiness.

Severity

A number of diagnostic tests, including the

Epworth Sleepiness Scale The Epworth Sleepiness Scale (ESS) is a scale intended to measure daytime sleepiness that is measured by use of a very short questionnaire. This can be helpful in diagnosing sleep disorders. It was introduced in 1991 by Dr Murray Johns of Epwor ...

, are available to help ascertain the seriousness and likely causes of abnormal somnolence.

Treatment

Somnolence is a symptom, so the treatment will depend on its cause. If the cause is the behavior and life choices of the patient (like working long hours, smoking, mental state), it may help to get plenty of rest and get rid of distractions. It's also important to investigate what's causing the problem, such as stress or anxiety, and take steps to reduce the feeling.

References

External links

{{SleepSeries2 Symptoms and signs of mental disorders Sleep Mental processes fr:Sommeil#Somnolence