The prevalence of multiple sclerosis (MS) has been reported from many countries in the world, and prominent geographical differences among regions are well known: over 100 per 100 000 in European and North American populations vs 0-20 per 100 000 in Asian populations. These differences suggest that genetic factors are important in the development of MS. Moreover, it is also known that higher latitude is associated with higher prevalence of MS. The latitude gradient for MS risk is thought to be related to low sun exposure, possibly because this is associated with low serum levels of vitamin D, which has an immunomodulatory effect.
In contrast, data on the prevalence of neuromyelitis optica (NMO) and its wider disease spectrum, NMO spectrum disorders (NMOSD), are scant, although few reports suggest that,1 2 in contrast to MS, the prevalence of NMO is comparatively similar globally and rarely exceeds 5/100 000.
A previous Japanese nationwide survey revealed
that the estimated crude prevalence of MS in Japan is 7.7/100 000, while
another recent study reported a crude NMOSD prevalence of 4.1/100 000
in a local area of Hokkaido located in Northern Japan.3 In their JNNP paper,
Miyamoto and colleagues first showed the results of a nationwide survey
conducted in Japan based on a well-designed epidemiological methodology
and the 2006 Wingerchuk criteria for NMO; the estimated prevalence was
1.64 per 100 000 for NMO and 3.42 for NMOSD.4
To compare the data with those from other countries, we have searched
publications using search terms 'neuromyelitis optica', 'prevalence' and
'100,000' on the PubMed database, and citations in the papers.
Moreover, we selected publications calculating the prevalence of
patients with NMOSD who had fulfilled the 2006 or 2015 diagnostic
criteria for NMO or NMOSD.
Abstract: Journal of Neurology, Neurosurgery & Psychiatry current issue by Mori, M., Kuwabara, S., Paul, F.