Sleep Disorders

• Description
• Who is at Risk?
• Molecular Biology of Sleep

Description
Sleeping problems are one of the most common medical concerns of the United States population. Insomnia is often taken for granted by the typical American as part of living in a fast paced world. Although insomnia is the most common of the sleep disorders, it is not the most disabling. Sleep disordered breathing is far more serious. Sleep disordered breathing is defined as any alteration in the respiratory pattern that occurs during sleep. It can be divided into two categories: sleep apnea (the cessation of breathing), or sleep hypopnea (a decrease in airflow during sleep). Excessive daytime sleepiness and loud and disruptive snoring characterize sleep apnea. Sleep apnea may cause a person's breathing to stop hundreds of times throughout the night.

Who is at Risk?
Sleep apnea is more common in men than women and has long been associated with obesity. The "typical" patient with severe sleep apnea is a middle-aged male who is significantly overweight, snores loudly, and suffers from marked daytime sleepiness. Recent studies have suggested that neck size is a better predictor of sleep apnea than obesity alone. Other anatomic abnormalities that decrease the airway size, can be: enlarged tonsils, tongue or jaw abnormalities, or some congenital deformities. All lead to an increased risk of sleep apnea.

Sources: IMA, Inc., Alexian Brothers Medical Center

Molecular Biology of Sleep
Associate Professor Luis de Lecea, Ph.D., and his colleagues attempt to understand the cellular and molecular components that modulate cortical activity and sleep. In particular, they focus on the characterization of neuropeptides first described by their group: cortistatin and the hypocretins. Cortistatin is a neuropeptide expressed in the cerebral cortex. The hypocretins, also called orexins, are two neuropeptides expressed in a few thousand cells in the lateral part of the hypothalamus. Recent studies indicated that patients with narcolepsy lack hypocretin-expressing cells, suggesting that narcolepsy is a neurodegenerative disease of the hypocretinergic system.

Neuropeptide S is a newly discovered neuropeptide expressed prominently in a few hundred neurons in the locus coeruleus. In collaboration with scientists at the University of California, Irvine, de Lecea and his colleagues investigated the role of neuropeptide S in sleep and wakefulness. Infusion of neuropeptide S into the brain ventricles in mice dramatically enhanced wakefulness. Their data strongly suggests that neuropeptide S is an important modulator of sleep and waking.

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