Neuromyelitis optica is a rare disease. In a review done in 2013, the worldwide incidence of neuromyelitis optica per 100,000 persons was estimated at 0.052 to 0.40 and the prevalence per 100,000 persons was estimated at 0.52 to 4.4. Denmark had the highest incidence and prevalence of neuromyelitis optica, compared to Cuba which had the lowest, amongst the countries studied (Marrie and Gryba 2013). The prevalence in the United States has been estimated at 1 to 2 per 100,000 (Mealy et al 2012). In Japan, the prevalence is 2.8 per 100,000; however, the ratio of neuromyelitis optica to multiple sclerosis is much higher compared to the rest of the world (Uzawa et al 2014).
Neuromyelitis optica is more common in women, accounting for more than 80% of cases. The disease can be seen during young adolescence to late adulthood, and the median age is 40 years. Neuromyelitis optica occurs in the pediatric population with an average onset age of 7 to 14 years (Jeffery and Buncic 1996; Lotze et al 2008). In the United States, neuromyelitis optica occurs in Caucasians but is overrepresented in decedents of African heritage. The Japanese population has an elevated occurrence as well. Indeed, opticospinal multiple sclerosis, more prevalent in Japan, is likely the same clinical entity as neuromyelitis optica, as clinical features are equal to neuromyelitis optica, and antibody seropositivity mirrors that of neuromyelitis optica (Wingerchuk et al 2006).