New Clues About Narcolepsy

Imagine feeling tired and sleepy all day, every day–even after seven or eight hours of sleep. You’re so tired that you can’t help falling asleep during the day, even while talking to someone, working or–even worse–driving. This is the brutal, everyday reality for people with narcolepsy.

A debilitating sleep disorder, narcolepsy affects about one person in 4000, and usually starts during the late teens or early 20s. The cause has been elusive until recently. Many years of research to unravel the mystery of narcolepsy have shown that it is caused by destruction of a group of brain cells (neurons) that produce an alerting neurotransmitter called hypocretin. Without these neurons keeping the brain awake, irresistible sleep attacks intrude into wakefulness.

But how are these vital hypocretin neurons destroyed or damaged in narcolepsy? Research yielded clues that the body’s own immune system may be attacking the hypocretin neurons in a process called “autoimmunity.” In a fascinating and sophisticated series of experiments, investigators demonstrated that narcolepsy patients have special T cells (one of the body’s important immune cells) that react to part of the hypocretin molecule. So the body’s own immune system may be attacking the hypocretin neurons by using these special T cells.

Further clues unraveling the autoimmune cause of narcolepsy came from an unlikely source. A rash of new cases of narcolepsy was identified after the 2009 H1N1 influenza outbreak. A series of experiments recently published in the journal Science: Translational Medicine demonstrated that special T cells in narcolepsy patients that are primed to attack the hypocretin molecule also react to a substance on the 2009 H1N1 influenza virus. This may be a case of molecular “mimicry,” where T cells, reacting to an influenza virus protein “cross-react” with the hypocretin molecule. So, T cells primed to defend against the 2009 H1N1 influenza virus may be “tricked” into attacking the hypocretin neurons potentially causing narcolepsy.

Yet this is fascinating, groundbreaking research does not fully explain all cases of narcolepsy, since it existed long before the 2009 H1N1 outbreak. However, it does show that the body’s own immune system may be “tricked” into attacking itself, a process that results in many autoimmune diseases. Narcolepsy can now be considered as one of these autoimmune diseases.

The appropriate diagnosis and treatment for sleep disorders can improve quality of life and daytime function. Often, complaints of severe sleepiness due to narcolepsy are ignored; patients are called “lazy.” Or perhaps they are misdiagnosed with another condition.

The lag from the first narcolepsy symptoms to a proper diagnosis can sometimes take a decade or longer. It is important to recognize the symptoms of narcolepsy for proper treatment. If you think you might have narcolepsy, help is available at the North Shore-LIJ Sleep Disorders Center. Call 877-SLEEP MD (877-753-3763) for more information.

This post was written by Harly Greenberg, MD, medical director of the North Shore-LIJ Sleep Disorders Center.

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