Narcolepsy onset most frequent in April, least in November, mostly unrelated to H1N1 vaccination
WEDNESDAY, Aug. 24 (HealthDay News) -- In China, narcolepsy onset is significantly associated with seasonal and annual patterns of upper airway infections, including H1N1 influenza, and increased three-fold following the 2009 H1N1 winter influenza pandemic, independent of H1N1 vaccination in the majority of cases, according to a study published online Aug. 22 in the Annals of Neurology.
Fang Han, M.D., from the Beijing University People's Hospital in China, and colleagues investigated the seasonal fluctuations in narcolepsy onset, and its relationship with the 2009 H1N1 infections in China. A total of 629 patients (86 percent children) diagnosed with narcolepsy between 1998 and 2010 were included in the analysis. Self-reported data on month and year of narcolepsy onset were collected and assessed for monthly variation in onset. Vaccination history was taken from 186 patients who developed narcolepsy after October 2009.
The investigators found that narcolepsy had a seasonal onset that was significantly influenced by month and calendar year. The onset was most frequent in April and least frequent in November, with a 6.7-fold increase from trough to peak. A three-fold increase in narcolepsy onset following the 2009 H1N1 winter influenza pandemic was found on assessment of year-to-year variation. Of 142 cases with onset since October 2009, only eight participants recalled receiving H1N1 vaccination. A significant delay of five to seven months was identified between the seasonal peak in influenza/cold or H1N1 infections and the peak in narcolepsy onset occurrence.
"In China, narcolepsy onset is highly correlated with seasonal and annual patterns of upper airway infections, including H1N1 influenza," the authors write.
One of the study authors disclosed financial ties with the pharmaceutical industry.
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