What’s the News: Things got very drowsy in China after the swine flu pandemic of 2009: narcolepsy, a neurological disease that involves sudden sleepiness, tripled in the months afterwards. Scientists have wondered whether additives in flu vaccines could be behind the spike of snooziness there and in other countries, but a new report says that even people who weren’t vaccinated came down with it. Could narcolepsy be caused by the flu virus itself?
How the Heck:
- Scientists had noticed the spike in narcolepsy cases in European countries after the flu pandemic before. But they had thought that it was due to substances in the vaccines that kick the immune system into over-drive.
- In China, however, the vaccines didn’t include those substances, and few people were vaccinated. Yet the surge in narcolepsy cases still occurred. To learn more, the team obtained hospital data on about 906 people who had been diagnosed with narcolepsy between 1998 and 2011 and further questioned a subset of them who had developed it after the flu pandemic, only 5.6% of whom had been vaccinated.
- They found that even before the pandemic, narcolepsy cases were seasonal, almost never occurring in November and peaking April. That’s about 5-7 months after flu season, which, along with the unusual surge after 2009, led the researchers to suggest that the flu itself could be the cause.
What’s the Context:
- Narcolepsy, frequently depicted in pop culture, is a chronic neurological disease characterized by sudden naps, usually lasting about 15 minutes, and sudden loss of muscle tone. Scientists think that some combination of a genetic predisposition and environmental cues are behind it, and there’s some evidence that other respiratory infections, like strep throat, have triggered cases in the past.
- They also suspect it is an autoimmune disorder, perhaps caused when immune cells destroy neurons that produce hypocretin, a protein that regulates sleep.
The Future Holds: The fact that narcolepsy is seasonal is interesting, but it’s not proof of a connection with flu (after all, April is also a season when many people have allergies, but it doesn’t mean the two are related). Establishing a connection between the them will likely require carefully timed molecular biology studies of people who’ve had flu and narcolepsy and comparison with folks who have had neither.
Reference: Fang Han et al. Narcolepsy onset is seasonal and increased following the 2009 H1N1 pandemic in China. Annals of Neurology. Article first published online: 22 AUG 2011. DOI: 10.1002/ana.22587
Image courtesy of Daniel Morris / flickr
[via New Scientist]