New Insights Into Sleeping Disorder Narcolepsy
It may have its roots in immune system problems, study suggests
And in 2010, a cluster of narcolepsy cases in Europe was linked to a particular H1N1 vaccine that contained an "adjuvant" designed to induce a stronger immune system response. That vaccine, called Pandemrix, is no longer in use.
All of that led experts to speculate that in some genetically vulnerable people, the H1N1 virus could cause T cells to mistakenly attack hypocretin-producing brain cells.
And in the current study, Mellins's team found that segments of the H1N1 virus were similar to portions of the hypocretin protein -- the same portions that activated narcolepsy patients' T cells. They say that supports the idea that certain infections confuse T cells into attacking hypocretin-producing cells.
An expert on sleep welcomed the new study.
"They're providing more-compelling evidence that this is an autoimmune disease," said Dr. Nathaniel Watson, an associate professor of neurology at the University of Washington in Seattle, and a member of the board of directors for the American Academy of Sleep Medicine.
He and Mellins both said the results could have practical use, too. For one, researchers may be able to develop a blood test to help objectively diagnose narcolepsy.
Right now, Watson said, narcolepsy can be difficult to pinpoint, because the most common symptom -- daytime sleepiness -- has far more common causes. The most common, he noted, is simple: Not going to bed early enough.
So to diagnose narcolepsy, people may have to spend 24 hours in a sleep lab or, in some cases, have a lumbar puncture (spinal tap) to measure hypocretin in the spinal fluid.
Mellins said that if an autoimmune reaction is the cause of type 1 narcolepsy, it might be possible to treat with an immune-suppressing therapy.
The problem, though, is that once people develop full-blown symptoms, their hypocretin-producing cells have already been knocked off.
"We'd need some kind of pre-clinical marker of the disease to be able to intervene," said Watson at the University of Seattle.
Roth of Henry Ford Hospital agreed. "The big challenge is, how will you identify the people to treat?"
Three of the study authors reported they are inventors on a patent to use the hypocretin protein segments to diagnose narcolepsy. Stanford owns the intellectual property rights for this use.