Increased incidence of narcolepsy following the 2009 H1N1 pandemic

Abstract

Narcolepsy is an autoimmune sleep disease characterized by excessive daytime sleepiness, cataplexy, and intrusive rapid eye movement sleep. Deficit in endogenous orexin is a major pathogenic component of the disease. This disorder is also associated with the gene marker HLADQB1*0602. After the 2009, H1N1 pandemic, a remarkable increased incidence of narcolepsy, especially in children, was noticed in different countries. In Finland and Sweden, this was attributed to the H1N1 vaccine, especially the adjuvanted pandemic vaccines. In China, there was a 3-fold increase in narcolepsy onset but was due to H1N1 virus infection per se. This review will first summarize the epidemiological data of post H1N1 narcolepsy, then possible mechanisms of the H1N1-related immune process to link the HLA (human leukocyte antigen) genetic background and hypocretin deficiency in narcolepsy–cataplexy will be discussed.