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Excessive daytime sleepiness affects 10-20% of the population. The causes are many, and the presentations variable. The consequences may be disabling or even lethal. Patients may not complain about drowsiness until they have had an automobile or occupational accident, or are threatened with job loss.

Sleepiness is a state of physiologic need, similar to hunger or thirst. The more we are sleep-deprived, the more our bodies will seek it. Sleepiness is usually reversed by getting an adequate quantity and quality of sleep. Moderate drowsiness can be masked by exercise, a stimulating environment, medication or motivation. Sleepiness can be unmasked by monotonous activities, alcohol, or relaxing environments.

The need for sleep is controlled by two pathways. In the homeostatic pathway, long wake times increase the desire to sleep. The other involves a circadian rhythm, or "internal clock" that regulates body functions on a daily cycle, including body temperature, blood pressure, peak alertness, hormone secretion and ability to sleep. The amount of sleep for optimal functioning is approximately 7 hours. Sleep which is out of phase with the circadian clock tends to be more interrupted. Sleepiness becomes pathologic when a person is normally expected to be alert.

The central desire of sleepiness should be differentiated from peripheral complaints of dyspnea, physical weakness or co-existing complaints of fatigue, boredom or depression. Once established, it is important to get a detailed history. Simple questions or questionnaires can determine the severity. These are subjective and may be imprecise, but are a good starting point. Important clues include the duration of hypersomnolence, usual time in bed and how this varies throughout the week. This can be confirmed with the presence of a spouse.

Diagnostic criteria for conditions causing hypersomnolence are published by the American Academy of Sleep Medicine in the International Classification of Sleep Disorders. These include disorders of breathing, circadian rhythm, disrupted sleep, prescribed medications or substance abuse, medical and psychiatric conditions, central hypersomnias, and those related to behavioral or external influences.

Breathing disorders are common. Obstructive sleep apnea should be suspected with a history of snoring, witnessed apnea, a large neck circumference or hypertension. A polysomnogram (PSG) is essential to confirm or rule out these disorders. PSG includes simultaneous monitoring of EEG, EOG, EMG, oximetry, telemetry, respiration and body position. Trained technicians can rapidly identify and initiate treatment.

Most insomnia disorders are assessed with a good sleep history. A polysomnogram is not usually necessary, unless an occult or co-existing sleep disorder is suspected. When hypersomnolence is present, consultation with a sleep center is recommended.

Circadian rhythm misalignments may be acute, chronic or recurrent. The patient has difficulty falling asleep or awakening at a conventional time. Drowsiness may impair social or occupational functioning. These disorders can be documented with questionnaires, sleep diaries, actigraphy and other physiologic measures. Actigraphy monitors a patient's level of activity. Long inactive periods are believed to represent sleep.

Drowsiness due to sedating medications, stimulant withdrawal, poor sleep hygiene, uncomfortable bedroom environment or chronic insufficient sleep can be identified and potentially reversed by correcting the primary cause.


Adam Griggs, D.O., FCCP, FAASM earned his medical degree at New York College of Osteopathic Medicine and completed his Pulmonary Fellowship at Tulane University in Louisiana. He is board certified in Internal Medicine, Pulmonary Diseases and Sleep Medicine. Dr. Griggs is a fellow of the American Academy of Sleep Medicine and the American College of Chest Physicians. He has been practicing in Central Florida since 1992 with privileges at 7 hospitals.

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