A population-based epidemiologic study of adult-onset narcolepsy incidence and associated risk factors, 2004–2013

An increase in narcolepsy incidence was noted after the novel pandemic influenza of 2009, leading to further interest in risk factors associated with this disease. However, there is limited data on the epidemiology of narcolepsy, particularly in the adult population. Therefore, we sought to examine narcolepsy incidence rates in the United States and describe associated characteristics. We performed a population based epidemiologic study of active duty military personnel. All outpatient clinics in the continental United States providing care for active duty military between 2004 through 2013 were included utilizing existing databases. Narcolepsy was defined in 3 ways: (1) 2 diagnoses of narcolepsy within 6 months of each other, one made by a sleep expert; (2) 2 diagnoses by any provider followed by a narcolepsy prescription within 14 days of last visit; and (3) procedure code for a sleep study followed by a narcolepsy diagnosis by a sleep expert within 6 months. There were 1675 narcolepsy cases. Overall incidence of narcolepsy trended from 14.6 to 27.3 cases per 100,000 person-years, with an increase starting after 2005–2006 and peaking during the 2011–2012 influenza season. Higher frequencies were seen among females, non-Hispanic blacks, and members living in the south. Narcolepsy incidence rates among active duty military members are higher than previously described. The reason for the steady rise of incidence from 2005 to 2006 through 2011–2012 is unknown; however, these findings require further exploration. We detected risk factors associated with the development of narcolepsy which may aid in future study efforts.