Around 3 million people worldwide suffer from narcolepsy or bouts of sleepiness and sleep attacks that can affect their ability to have a normal life. There is no cure for the disorder, and few clues about its causes. But now, a new study suggests it could be an autoimmune disease.
In the journal Pharmacological Research, Yehuda Shoenfeld, a professor at Tel Aviv University (TAU) and a world expert in autoimmune disease, and colleagues describe how they found an autoimmune process in the brain that appears to trigger narcolepsy.
They say narcolepsy bears the hallmarks of an autoimmune disorder and should be treated like one.
Narcolepsy first strikes people between the ages of 10 and 25, and plagues them for life.
The condition occurs with some or all of the following symptoms: falling asleep without warning, excessive daytime sleepiness, hallucinations, slurred speech, sudden loss of muscle tone, temporary weakness of most muscles, temporary inability to move or speak while falling asleep or waking up.
Narcolepsy caused by antibody attack on orexin-producing brain cells
The process the researchers discovered is a trigger for the loss of orexin neurons - brain cells that maintain a delicate balance between sleep and wakefulness.
Prof. Shoenfeld says narcolepsy is a devastating condition and particularly debilitating to children. He explains how it is more than a genetic disorder:
"Narcolepsy is interesting, because although it has been considered to be strictly genetic, it is induced by environmental factors, such as a burst of laughter or stress."
The team first became interested in narcolepsy when Finland saw a rush of narcolepsy diagnoses in 2009 after the public were given the H1N1 flu vaccine. Following the vaccination campaign, the incidence of narcolepsy shot up to 16 times the average, says Prof. Shoenfeld.
The team had also become aware of a study reported by a group of sleep researchers in Japan who had discovered antibodies in the brain that appear to attack "tribbles" - small granules that contain brain cells that produce orexin, a brain chemical that helps maintain the delicate balance between sleep and wakefulness.
Prof. Shoenfeld says they have noticed how patients and animals with narcolepsy have less orexin in the brain, resulting in an imbalance between sleep and wakefulness, which leads to attacks of narcolepsy.
So they asked themselves - why is the orexin disappearing? Could the culprit be an immune reaction? They think yes - that autoantibodies are binding to the tribble granules and destroying them and the orexin neurons they contain.
Mice injected with the antibodies showed increasing signs of narcolepsy
For their study, the team collaborated with the researchers in Japan to isolate the specific antibodies, which they then injected directly into mice.
Over the following months, the mice began to experience increasing sleep attacks and irregular sleep patterns. Prof. Shoenfeld describes what they saw:
"Mice fall asleep like dogs, circling around before going to sleep. Suddenly, in this experiment, the mice just dropped off to sleep and then, just two minutes later, woke up as though nothing had happened."
He says they want to change the view of narcolepsy - to define it as a known autoimmune disease, because "a better understanding of the mechanism causing this disease, which debilitates and humiliates so many people, will lead to better treatment and, maybe one day, a cure."
The researchers now plan to discover the area in the brain where the antibodies attack the orexin-producing brain cells.
Meanwhile, Medical News Today recently learned how mindfulness meditation can improve sleep quality in older adults. In the US, around half of over-55s are thought to have problems sleeping well, mostly due to health and social problems like depression, fatigue, mood disturbances and reduced quality of life.