Body + Brain

19
Dec

Narcolepsy Is an Autoimmune Disorder

We all crave sleep. But there are times when sleepiness is a liability, and I’m not talking about drowsiness. I’m talking about narcolepsy.

Narcolepsy can be a debilitating condition. Sufferers have often uncontrollable urges to fall asleep during the day, even in the middle of physical activity. A majority of people with narcolepsy may even fall down or slump in their seats due to a sudden weakness of their muscles, called cataplexy. Others experience microsleep episodes, where they continue what they’re doing without consciousness, as though their bodies are on autopilot.

sleepy-man
Narcolepsy can trigger uncontrollable urges to sleep.

The disorder is more prevalent than you might think—about 1 in 2,000 people in the U.S. and Western Europe are narcoleptic, and 1 in 600 are in Japan.

For years, we’ve suspected narcolepsy was an autoimmune disorder, where the patient’s body is fighting against itself. But we had no proof. Now, though, a wave of new narcolepsy patients, triggered by an immune response to the 2009-2010 GlaxoSmithKline H1N1 flu vaccine, has provided conclusive evidence.

Kate Kelland, reporting for Reuters:

Results from U.S. researchers showed the debilitating disorder, characterized by sudden sleepiness and muscle weakness, can be set off by an immune response to a portion of a protein from the H1N1 virus that is very similar to a region of a protein called hypocretin, which is key to narcolepsy.

While scientists now know the disorder is autoimmune, they don’t know the exact process by which the immune system attacks the neurons that produce hypocretin, a hormone that helps us stay awake. The immune system seems to become sensitized to the hypocretin-like protein in the vaccine, but the T-cells don’t attack the hypocretin-producing neurons directly, making the exact process something of a mystery. They also don’t know who, exactly, is at risk, but about 25% of people have a gene variant that is shared with 98% of narcoleptics, says Ed Yong at Nature, so genetics could factor into it.

Not all flu vaccines seem to trigger narcolepsy in susceptible individuals, either, and it’s important to point out that the H1N1 vaccine that caused the rise in cases isn’t used anymore. Researchers also plan to use this new information to prevent flu vaccines from containing hypocretin-like proteins.

Scientists involved in the study hope their findings could lead to a blood test to diagnose the disorder and treatments that, if started early enough, could halt the destruction of hypocretin-producing neurons.