Worldwide prevalence of neuromyelitis optica spectrum disorder (NMOSD) and neuromyelitis optica (NMO): a systematic review and meta-analysis

BackgroundNeuromyelitis optica spectrum disorder (NMOSD) is a progressive demyelinating disease of the central nervous system that has overlapping symptoms with multiple sclerosis (MS) but differs from it in a variety of ways. Previous studies have reported conflicting results trying to estimate the number of individuals affected by them which is why we designed this systematic review and meta-analysis to estimate the worldwide prevalence and incidence of NMOSD/NMO based on current evidence.MethodsWe searched PubMed, Scopus, EMBASE, Web of Science, and gray literature including references from the identified studies, review studies, and conference abstracts which were published up to February 1, 2022. We used all MeSH terms pertaining to NMOSD, NMO, and all the terms on prevalence, incidence, and epidemiology to identify the search components. Pooled effect sizes were measured using random-effect model by DerSimonian-Laird.ResultsThe prevalence and incidence rates of NMOSD/NMO ranged from 0.07 to 10 and 0.029 to 0.880 per 100,000 population, respectively. The overall pooled prevalence of NMO per 100,000 population was 1.54 (I-2: 98.4%, 95% CI: 1.13-1.96, P< 0.001) based on the 2006 criteria, 1.51 (I-2: 99.4%, 95% CI: 1.21-1.81, P < 0.001) based on the 2015 criteria and 2.16 (I-2: 89.4%, 95% CI: 1.46-2.86, P < 0.001) based on the 2006/2015 criteria. The overall annual incidence of NMO per 100,000 population was 0.155 (I-2: 95%, 95% CI: 0.115-0.195, P < 0.001) based on the 2006 criteria and 0.278 (I-2: 100%, 95% CI: 0.135-0.420, P < 0.001) based on the 2015 criteria. The prevalence rates were highest in French West Indies and South Korea, and lowest in Cuba and Australia, based on the 2006 and 2015 criteria, respectively. Also, the highest annual incidence rates were obtained for Sweden and Slovak republic and the lowest for Cuba and Australia based on the 2006 and 2015 criteria, respectively. All estimated rates were higher among females compared to males.ConclusionAlthough rare, NMOSD/NMO impact affected individuals in devastating ways. Several large-scale prospective studies are required to reach a comprehension of the epidemiological aspects of these notorious demyelinating conditions.

Automated summary

This systematic review and meta-analysis aimed to estimate the prevalence and incidence rates of NMOSD/NMO worldwide. The analysis showed that the rates varied and were higher among females. More large-scale studies are needed to fully understand the epidemiological aspects of these conditions.