August 26, 2011 — China experienced a 3-fold increase in narcolepsy after the H1N1 influenza pandemic, report researchers.
Recently, concern has been rising about a spike in narcolepsy in Northern Europe after H1N1 vaccination. However, this new report suggests the increase in China may not be attributed to preventative measures.
"The increase in narcolepsy incidence was unlikely caused by increased vaccination as only 6% of study narcolepsy participants reported receiving a vaccination against H1N1," senior investigator Emmanuel Mignot, MD, from the Stanford Center for Sleep Sciences and Medicine in Palo Alto, California, said in a news release. "A 5 to 7 month delay between the seasonal peak in flu and peak in the onset of narcolepsy was also observed."
The results were published online August 22 in the Annals of Neurology.
Narcolepsy, caused by the loss of hypocretin and orexin neurons in the hypothalamus, is likely the result of an autoimmune process. It is estimated that less than 1% of the world population has narcolepsy. The National Institutes of Neurological Disorders and Stroke suggests that 1 in 3000 Americans have the disorder and may experience sudden bouts of sleep at any time, a sudden loss of voluntary muscle tone, vivid dreams or hallucinations, and short periods of paralysis.
"Our findings show a seasonal variation in narcolepsy onset in a Chinese population occurring most frequently in late spring and early summer," Fang Han, MD, from Beijing University People's Hospital in China, said in a news release.
In this retrospective analysis, investigators collected self-reported data from 629 patients. Most (86%) were children. Of these patients, 182 developed narcolepsy and were asked for vaccination history.
Investigators found that onset was least frequent in November and occurred most often in April, with close to a 7-fold increase from lowest point to peak time.
"These findings are reminiscent of the encephalitis lethargica epidemic that followed the great Spanish influenza pandemic of 1917-1918," Dr. Mignot said. "Not only narcolepsy, but also psychosis and Parkinson's disease may follow winter infections, and further research is needed in the area of autoimmune diseases of the brain."
This work was funded by National Science Foundation of China, the Sino-German Center for Research Promotion, and the Beijing Municipal Science and Technology Commission. Dr. Mignot has done some work for Jazz, Merck, Mead, and the Federal Trade Commission. Since submitting this article, Dr. Mignot has been in talks with GlaxoSmithKline, the maker of the Pandemrix vaccine, regarding the funding of research to be conducted at Stanford University.
Ann Neurol. 2011;70:410-417. Abstract
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Cite this: More Narcolepsy in China After H1N1 - Medscape - Aug 26, 2011.