Excessive daytime sleepiness (EDS) is a prevalent topic in clinical care. Tiredness, fatigue, lack of energy, and sleepiness are complaints commonly encountered by psychiatrists and other physicians. Many surveys and epidemiological studies indicate that pathological daytime sleepiness, which is sleepiness that interferes with an individual's function most of the time, occurs in 7% to 13% of the population. Studies of patients within primary care practices suggest that this population suffers an even greater prevalence of sleepiness than the general public. Estimates of 20% to 25% or higher have been suggested by studies of large samples of primary care patient populations. Causal or contributing factors leading to a patient's experience of EDS range from the process of simply chronically allowing too little time for sleep on an ongoing basis, to idiopathic but profound central nervous system (CNS)-mediated debilitating hypersomnolence. Common among the causes of EDS are insufficient sleep, circadian rhythm disorders such as delayed sleep-phase syndrome, sleep disorders such as obstructive sleep apnea (OSA), CNS-related disorders such as post-infectious syndromes or CNS injury or lesions, and drugs—prescribed or otherwise.

Sleepiness is normal when it occurs toward the end of the day, at the beginning of the habitual sleep period. At this point, physiological sleep need has accumulated and the circadian rhythm no longer opposes sleep onset, facilitating the entry into sleep. However, when sleepiness occurs outside of the habitual sleep period it can become a medically significant problem.

The International Classification of Sleep Disorders, Second Edition (ICSD-2) defines excessive daytime sleepiness (EDS) as an inability to stay awake and alert during the major waking episodes of the day, resulting in unintended lapses into drowsiness or sleep. To differentiate this from the sporadic sleepiness that most people experience after a night or two of poor sleep, the ICSD-2 adds a frequency and duration criteria with most disorders requiring excessive sleepiness to be present daily or almost every day for at least 3 months (Slide 1).

The symptoms of excessive daytime sleepiness (EDS) need to be assessed both clinically and with objective diagnostics. As with any other medical disorder, when patients present with excessive sleepiness, the first step is to determine the chief complaint. The spectrum of clinical presentations for EDS is wide, and patients may complain of fatigue, low energy, laziness, apathy, lethargy, poor memory, reduced concentration, reduced attention, irritability, poor performance in work/school, automatic behavior, frequent accidents, drowsiness, and/or sleep attacks. Oftentimes patients do not recognize their own excessive sleepiness and will not quantify the problem unless they are specifically asked if they are sleepy. Some of these patients only present because they have been referred by their employers due to their excessive sleepiness.

After the patient has noted his chief complaint, the clinician should assess the patient's score on the Epworth Sleeping Scale (ESS) on a quantifiable basis. The ESS is a self-administered questionnaire used to rate the severity of EDS. Respondents are asked to use a numeric scale from 0 to 3, corresponding to the likelihood (never, slight, moderate, and high) that they may fall asleep in eight given situations (Slide 1). An ESS score can range from 0 to 24. A score >9 indicates an abnormal level of sleepiness. A score >14 suggests marked sleepiness. Most patients with narcolepsy will score in this range. The normal range varies for different sleep disorders (Slide 2).

The most common cause of sleepiness is sleep deprivation, which is often due to behaviorally induced sleep limitations. One method of preventing impaired or shortened sleep is to ensure good sleep hygiene. It is important to review with patients the principles of sleep hygiene so that they can rule out causal behaviors that might be relatively simple to correct. Principles of good sleep hygiene include maintaining a regular sleep/wake schedule, exposure to light in the morning hours, avoiding caffeine and nicotine especially 4–6 hours before bedtime, avoiding alcohol and heavy meals before sleep, regular exercise (vigorous exercise should be avoided 3–4 hours before sleep), limiting time in bed to the time spent sleeping, and allowing sufficient time to get comfortable and relaxed prior to sleep. Even if one can fall asleep after drinking alcohol or caffeine, sleep maintenance can be curtailed. Sensitivity to these stimulants is often apparent in the latter half of the night. People often fail to recognize that vigorous aerobic workouts close to bedtime makes it harder to fall asleep. This is because a revved up metabolism heats the body up, and thereby delays the normal cooling of the core body temperature which triggers the onset of sleep.

One study assessed the sleep of 259 subjects using the Multiple Sleep Latency Test (MSLT), an objective measure of daytime sleepiness that assesses how quickly someone can fall asleep in conducive conditions. The results indicated that many people in the general population carry a very heavy burden of sleepiness (Slide 1). Many physicians were shown to carry pathological levels of sleepiness because of their heavy call schedules and their foreshortened sleep on nights that they are not on call. The average adult needs 8.2 hours of sleep per night, and not surprisingly many studies have found that the sleepiest adults spent ≤6 hours in bed. What makes matters worse is that insight into the impairments of sleepiness erodes rapidly, but other cognitive and somatic impairments continue to mount with regular chronic under-sleeping. When sleepiness is due to chronic sleep deprivation, treatment often consists of scheduling enough time in bed to allow for an adequate amount of sleep.