Conference Coverage

Distinguish ‘sleepiness’ from ‘fatigue’ to help diagnose hypersomnia



Determining whether patients are fatigued or experiencing sleepiness is an important criterion when diagnosing hypersomnia, according to Ruth M. Benca, MD, PhD.

A man yawns ©Digitial Vision/
“Patients can’t always tell the difference, and unfortunately, a lot of clinicians don’t really clarify whether a patient is truly sleepy or just fatigued,” Dr. Benca, chair of the department of psychiatry and human behavior at the University of California, Irvine, said at the virtual Psychopharmacology Update presented by Current Psychiatry and Global Academy for Medical Education.

Dr. Ruth Benca, University of California, Irvine

Dr. Ruth Benca

“We want to distinguish sleepiness from fatigue or tiredness. People who are tired or fatigued may wish they could sleep or feel they need to sleep, but they are actually not falling asleep in relaxed situations.”

Fatigue, feeling tired, and lack of energy are common complaints that accompany insomnia and psychiatric disorders, but these patients do not fall asleep quickly in a restful setting and will have normal multiple sleep latency test (MSLT) in a laboratory. In contrast, excessive sleepiness, or hypersomnia, occurs when patients sleep more than 11 hours in a 24-hour period.

Patients with hypersomnia fall asleep in low stimulus situations and devote more energy to staying awake during situations. This excessive sleepiness can be dangerous in the context of activities such as driving, Dr. Benca said. These patients will also have low sleep latencies (< 8 minutes) when tested through MSLT in a laboratory, she added. Patients with hypersomnia may be irritable, have reduced attention or concentration, and have poor memory.

The primary cause of hypersomnia is sleep deprivation, but “both hypersomnia and fatigue are common complaints in psychiatric patients, including depression, bipolar disorder, seasonal affective disorder, [and] psychosis,” Dr. Benca explained. Other causes of hypersomnia include sleep disorders such as sleep apnea, circadian rhythm disorders and periodic limb movements, neurologic or degenerative disorders, mental disorders, and effects of medication. Idiopathic hypersomnia and narcolepsy are uncommon causes of hypersomnia and usually diagnosed in a sleep laboratory setting, she said.

In patients with depression, hypersomnia looks like patients having “nonimperative sleepiness,” Dr. Benca said. “They may spend a lot of time in bed; they may report long and nonrefreshing naps or long sleep time.”

There also is an issue with sleep inertia in patients with depression and hypersomnia, and with patients taking a long time to wake up and begin their day. In these patients, “when we put them in the sleep laboratory, the objective studies generally do not show that they are excessively sleepy, despite their reports of subjectively being sleepy,” she said.

There is not much objective MSLT or subjective measure data for hypersomnia in patients with schizophrenia despite these patients reporting daytime sleepiness or hypersomnolence, Dr. Benca admitted. Hypersomnia in patients with schizophrenia may be related to drug effects, poor sleep hygiene, circadian rhythm abnormalities, or comorbid sleep disorders. “Excessive sleepiness may also be related to the schizophrenia itself,” she said.

Treatments for hypersomnia

The first priority for patients with hypersomnia is to avoid sleep deprivation and practice good sleep hygiene – factors that are important both in insomnia and hypersomnia. “Make sure that patients are having adequate time in bed and having regular hours of sleep,” Dr. Benca said.


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