In a critical review of all epidemiological studies of optic neuritis before 1985 (Kurtzke 1985), the incidence was approximately 3 in 100,000 people in northern latitudes where multiple sclerosis is common (northern United States, Western Europe), and fell to 1 in 100,000 people in medium-risk areas for multiple sclerosis (Hawaii, Israel). In Minnesota, the incidence is 5 per 100,000, and the prevalence is 115 per 100,000 (Rodriguez et al 1995). A south-to-north gradient exists in Australia. Optic neuritis is 2.5 times more common in women than in men. Certain major histocompatibility complex class II antigens are over-represented in optic neuritis, suggesting a genetic predisposition for specific immune responses (Kinnunen et al 1989).
Episodes of optic neuritis are more common in the United States and Great Britain during spring and summer (Taub and Rucker 1954; Bradley and Whitty 1967; Hutchinson 1976; Farris and Pickard 1990), and in Sweden during the spring (Jin et al 1999). In Poland optic neuritis appears in winter and spring (Leszkowska et al 1988). The maximum frequency of monosymptomatic optic neuritis is twice as high in the spring as in the fall, possibly an influence of virus infections or loss of sun exposure (Koch and Steinbrecher 2005).
The age distribution is slightly different from that of multiple sclerosis; there are more patients at the young and old ends of the spectrum (Kurtzke 1970). Optic neuritis is proportionately more frequent than multiple sclerosis in Asia, where it presents as an isolated symptom or as part of Devic disease (neuromyelitis optica) (Kurtzke 1970). In Japanese patients, compared to Caucasians, disc swelling is more common, but eye pain and periventricular plaques are less common (Wakakura et al 1999). In an area of high multiple sclerosis frequency, asymptomatic brain lesion appear in 73% of MRI scans done at the first episode of optic neuritis; cohorts in areas with lower multiple sclerosis frequency are less likely to have brain lesions (Swanton et al 2006). In these early studies, a higher prevalence of the “oriental” (Devic-like) form of multiple sclerosis or Devic disease itself in Japan and China would also reduce brain lesions on MRI.