Excessive Sleepiness in Clinical Practice: Causes, Risks and Diagnosis
Prepared by Dr. Alvyda Pilkauskienė
Introduction
Excessive daytime sleepiness, also referred to as hypersomnia (F51.1), is characterized by increased daytime sleepiness, sudden sleep episodes unrelated to insufficient sleep duration, or prolonged difficulty transitioning to wakefulness after awakening. When no clear organic cause is identified, this condition is most commonly associated with mental disorders.
Adverse Effects of Sleepiness
Patients frequently complain of both sleepiness and fatigue. Sleepiness is defined as a reduced state of wakefulness independent of nighttime sleep quality. It may manifest as prolonged daytime sleep, recurrent episodes of sleepiness, difficulty waking in the morning, sleepiness occurring at the beginning or end of the day, or symptoms that are seasonal or persist for several days.
Patients often use the terms sleepiness and fatigue interchangeably, making it important for clinicians to carefully clarify whether the primary complaint is true sleepiness or fatigue.
Sleepiness is characterized by a desire to fall asleep, whereas fatigue is associated with exhaustion and tension, usually following or accompanying heavy workload, without necessarily causing sleep episodes. Sleepiness generally improves after adequate sleep, while fatigue improves with rest.
Because both conditions significantly impair health and productivity, identifying their causes, which may be multiple, is essential for appropriate treatment.
Lithuanian sleep specialist Prof. Vanda Liesienė defines sleepiness as a reduced level of wakefulness independent of nighttime sleep quality, manifesting through prolonged daytime sleep, recurrent episodes of sleepiness, more difficult morning awakening, sleepiness at the beginning or end of the day, or symptoms lasting several days or occurring seasonally.
Sleepiness negatively affects psychological well-being, behavior, and cognitive functioning, ultimately reducing quality of life (Fig. 1).
Table 1. Expert-Recommended Sleep Duration by Age (2015)
| Age Group | Recommended Duration (hrs) | May Be Appropriate (hrs) | Not Recommended (hrs) |
|---|---|---|---|
| 0–3 months (newborns) | 14–17 | 11–13 or 18–19 | Less than 11 or more than 19 |
| 4–11 months (infants) | 12–15 | 10–11 or 16–18 | Less than 10 or more than 18 |
| 1–2 years (toddlers) | 11–14 | 9–10 or 15–16 | Less than 9 or more than 16 |
| 3–5 years (preschool children) | 10–13 | 8–9 or 14 | Less than 8 or more than 14 |
| 6–13 years (school-age children) | 9–11 | 7–8 or 12 | Less than 7 or more than 12 |
| 14–17 years (teenagers) | 8–10 | 7 or 11 | Less than 7 or more than 11 |
| 18–25 years (young adults) | 7–9 | 6 or 10–11 | Less than 6 or more than 11 |
| 26–64 years (adults) | 7–9 | 6 or 10 | Less than 6 or more than 10 |
| 65+ years (older adults) | 7–8 | 5–6 or 9 | Less than 5 or more than 9 |
Source: National Sleep Foundation (USA). In 2015, an expert panel consisting of 18 specialists in sleep medicine and related medical fields from 12 organizations provided updated recommendations for daily sleep duration.
Impact of Sleepiness on Behavior
Sleepiness impairs psychomotor functioning and increases the risk of occupational accidents, particularly when operating machinery or working with sharp tools.
Reduced work performance creates additional stress, which may eventually contribute to job loss.
Impact on Cognitive Functions
Sleep disorders such as narcolepsy and obstructive sleep apnea, which commonly involve excessive sleepiness, significantly impair cognitive functioning, particularly attention and memory.
A study published in 2011 by Neu and colleagues compared patients with chronic fatigue syndrome (n=15), sleep apnea syndrome (n=15), and healthy controls (n=16). Both chronic fatigue syndrome and sleep apnea were associated with impaired cognitive functioning and psychomotor performance.
Memory impairment may partly be explained by brief episodes of microsleep, because information acquired within approximately five minutes before falling asleep may fail to consolidate into memory.
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Reduced Productivity |
Unsafe Behavior |
Poor Mood |
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Risk of Accidental Injuries |
Financial Problems |
Health Disorders |
Physiological Effects of Sleepiness
Sleepiness may contribute to hypoxemia, particularly in patients with obstructive sleep apnea.
Patients with obstructive sleep apnea accompanied by excessive daytime sleepiness frequently also experience obesity and insulin resistance. A study by Barcelo and colleagues published in 2008 compared obstructive sleep apnea patients with and without excessive daytime sleepiness. The results suggested that daytime sleepiness may serve as an important clinical marker for evaluating metabolic syndrome risk in these patients.
Sleep deprivation may also reduce antibody production and impair immune response.
Pain perception is additionally associated with sleep disorders. For example, patients with narcolepsy accompanied by cataplexy tend to show greater pain sensitivity compared with the general population.
Identifying the Cause of Sleepiness
Because sleepiness is a nonspecific symptom associated with many disorders, determining its cause may be challenging.
Clinicians are first advised to assess whether sleepiness may be related to medication use or substance abuse before investigating other possible diseases (Table 2) associated with this symptom.
Importantly, sleepiness may result from multiple coexisting conditions rather than a single disorder.
Table 2. Conditions Associated With Sleepiness and Fatigue
| Sleepiness | Fatigue | |
|---|---|---|
| Circadian rhythm sleep disorders | ← Sleep disorders → | Chronic fatigue syndrome |
| Hypersomnias (narcolepsy, parasomnias) | Insomnia | |
| Obstructive sleep apnea | ||
| Restless legs syndrome | ||
| Periodic limb movement disorder | ||
| Chronic kidney failure | ← Internal diseases → | Heart disease |
| Heart failure | Thyroid dysfunction | |
| Liver failure | Liver failure | |
| Obesity hypoventilation (Pickwickian) syndrome | Chronic obstructive pulmonary disease | |
| CNS tumors | ← Neurological diseases → | CNS tumors |
| Epilepsy | Epilepsy | |
| Multiple sclerosis | Multiple sclerosis | |
| Parkinson’s disease | Parkinson’s disease | |
| Stroke | Stroke | |
| Anxiety disorders | ← Psychiatric disorders → | Anxiety disorders |
| Depression | Depression | |
| Post-traumatic stress disorder | Eating disorders | |
| Psychoses | Post-traumatic stress disorder | |
| Psychoses |
Sleep Disorders
Sleepiness is the primary symptom of several sleep disorders, including obstructive sleep apnea, restless legs syndrome, and periodic limb movement disorder.
Narcolepsy, circadian rhythm disorders such as shift work disorder, cyclic or episodic hypersomnia, recurrent hypersomnia (Kleine-Levin syndrome), and sleep disorders related to menstruation are also conditions in which excessive sleepiness may occur.
Narcolepsy affects approximately 0.02–0.18% of adults. Symptoms include recurrent sleep episodes and muscle weakness, together with:
• excessive daytime sleepiness, usually the earliest symptom;
• cataplexy;
• hypnagogic and hypnopompic hallucinations;
• sleep paralysis;
• disrupted nighttime sleep.
Because sleepiness is a central symptom of narcolepsy, clinicians are encouraged to use assessment tools such as the Epworth Sleepiness Scale or Stanford Sleepiness Scale to facilitate diagnosis.
Sleep-related movement disorders and restless legs syndrome are characterized by uncontrollable body or limb movements during sleep or periods of rest. Patients with these disorders may demonstrate abnormally elevated scores on the Epworth Sleepiness Scale (ESS).
Table 3. Epworth Sleepiness Scale
| Situation | Score |
|---|---|
| Sitting and reading | |
| Watching television | |
| Sitting quietly in a public place (e.g., a theater or meeting) | |
| As a passenger in a car for an hour without a break | |
| Lying down to rest in the afternoon when circumstances allow | |
| Sitting and talking to someone | |
| Sitting quietly after lunch without alcohol | |
| In a car, while stopped for a few minutes in traffic |
The patient rates each situation independently: 0 – would never doze, 1 – slight chance of dozing, 2 – moderate chance of dozing, 3 – high chance of dozing.
Neurological and Other Disorders
Many pathological conditions may cause secondary sleepiness, including congestive heart failure, renal or hepatic insufficiency, traumatic brain injury, stroke, cancer, inflammatory diseases, and encephalitis.
Among neurological disorders, excessive sleepiness is especially common in patients with Parkinson’s disease and Alzheimer’s disease. Patients with multiple sclerosis and epilepsy frequently report fatigue.
Studies indicate that 15–50% of patients with Parkinson’s disease identify sleepiness as one of the main factors negatively affecting quality of life.
The prevalence of sleepiness is approximately:
• 50% in patients with chronic obstructive pulmonary disease (COPD);
• nearly 40% in patients with neurological disorders, migraines, depression, and cardiovascular diseases;
• approximately 24% in patients with thyroid disorders;
• approximately 19% in cancer patients.
Rheumatoid arthritis and fibromyalgia are also associated with both sleepiness and fatigue.
Mental Disorders
Regulation of sleep is particularly important in psychiatric treatment because sleep disturbances significantly influence mental health outcomes.
Sleepiness is a common symptom in many psychiatric disorders. In an epidemiological study involving 7,954 individuals assessed over one year, 46.5% of participants reporting sleepiness were found to have mental disorders, compared with only 16% among individuals without sleep complaints.
Depression, bipolar affective disorder, post-traumatic stress disorder, alcohol dependence, and several other psychiatric conditions are associated with disturbances in sleep and wakefulness.
At the same time, treatment of psychiatric disorders may itself negatively affect sleep because psychotropic medications alter sleep structure and function.
Patients with depression more commonly report insomnia and fatigue rather than sleepiness. Up to 70% of patients with depression report difficulty falling asleep and maintaining uninterrupted sleep (Pagel, 2009).
Nevertheless, clinical experience suggests that excessive sleepiness may also frequently accompany depression.
Sleepiness may additionally be caused by substances such as marijuana and stimulants. Therefore, clinicians should always ask patients about the use of psychoactive substances and potential addiction-related behaviors.
Many patients independently complete questionnaires used to assess mood disorders, such as the Patient Health Questionnaire-9 (PHQ-9), which may assist clinicians in identifying clinically significant symptoms.
Assessment of Sleepiness
Sleepiness is most commonly assessed using the Epworth Sleepiness Scale (ESS) (Table 3).
The ESS was developed for adults in 1990 and slightly modified in 1997 by Dr. Johns, who named it after Epworth Hospital in Melbourne, where he founded the Sleep Medicine Center in 1988.
The questionnaire consists of 8 questions completed independently by the patient. Each item is scored from 0 to 3, resulting in a total score ranging from 0 to 24.
Completion of the questionnaire usually takes approximately 2–3 minutes.
Objective Assessment Tools
The gold standard for objective assessment of sleepiness is the Multiple Sleep Latency Test performed in a sleep laboratory.
This test measures how quickly a person falls asleep and determines the time required to enter rapid eye movement (REM) sleep after sleep onset. It is also useful for differentiating obstructive sleep apnea from other causes of excessive sleepiness, particularly narcolepsy.
Sleep onset occurring within less than 5 minutes is considered indicative of severe sleepiness.
Polysomnography is conducted while the patient sleeps in a specialized sleep laboratory. During the study, electrodes are attached to the patient and multiple physiological parameters are continuously monitored throughout the night, including:
• electroencephalography;
• electrooculography;
• leg muscle activity;
• electrocardiography;
• snoring intensity;
• nasal airflow;
• thoracic and abdominal respiratory movements;
• oximetry;
• body position.
Diagnosis of specific sleep disorders and other sleep-related conditions requires specialist consultation and appropriate treatment.
Conclusion
Sleepiness and fatigue are common patient complaints encountered in clinical practice.
Family doctors should carefully evaluate how sleepiness affects behavior, mood, cognitive functioning, and physiological health.
After obtaining a detailed clinical history, clinicians may use patient questionnaires and objective diagnostic methods to determine the severity of sleepiness.
Sleepiness and fatigue commonly accompany a wide range of medical conditions, and clinicians should always consider the possibility of multiple contributing causes.
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References in the editorial
