Obesity without sleep apnea is associated with daytime sleepiness.

Background: Daytime sleepiness and fatigue is a frequent complaint of obese patients even among those who do not demonstrate sleep apnea.

Objective: To assess in the sleep laboratory whether obese patients without sleep apnea are sleepier during the day compared with healthy controls with normal weight.

Methods: Our sample consisted of 73 obese patients without sleep apnea, upper airway resistance syndrome, or hypoventilation syndrome who were consecutively referred for treatment of their obesity and 45 controls matched for age. All patients and healthy controls were monitored in the sleep laboratory for 8 hours at night and at 2 daytime naps, each for 1 hour the following day.

Results: Obese patients compared with controls were sleepier during the day and their nighttime sleep was disturbed. During both naps, sleep latency, wake time after onset of sleep, and total wake time were significantly lower, whereas the percentage of sleep time was significantly higher in obese patients compared with controls. In contrast, during the nighttime testing, obese patients compared with controls demonstrated significantly higher wake time after onset of sleep, total wake time, and lower percentage of sleep time. An analysis of the relation between nighttime and daytime sleep suggested that daytime sleepiness in obese patients is a result of a circadian abnormality rather than just being secondary to nighttime sleep disturbance.

Conclusions: Daytime sleepiness is a morbid characteristic of obese patients with a potentially significant impact on their lives and public safety. Daytime sleepiness in individuals with obesity appears to be related to a metabolic and/or circadian abnormality of the disorder.