Worldwide incidence and prevalence of NMO: A systematic review

Objective: Since the last epidemiologic review of neuromyelitis
optica/neuromyelitis optica spectrum disorder (NMO/NMOSD), 22 additional
studies have been conducted. We systematically review the worldwide
prevalence, incidence, and basic demographic characteristics of NMOSD and
provide a critical overview of studies. Methods: PubMed, Ovid MEDLINE, and
Embase using Medical Subject Headings and keyword search terms and
reference lists of retrieved articles were searched from 1999 until August
2019. We collected data on the country; region; methods of case assessment
and aquaporin-4 antibody (AQP4-Ab) test; study period; limitations;
incidence (per 100,000 person-years); prevalence (per 100,000 persons);
and age-, sex-, and ethnic group–specific incidence or prevalence.
Results: We identified 33 relevant articles. The results indicated the
highest estimates of incidence and prevalence of NMOSD in Afro-Caribbean
region (0.73/100 000 person-years [95% CI: 0.45–1.01] and 10/100 000
persons [95% CI: 6.8–13.2]). The lowest incidence and prevalence of NMOSD
were found in Australia and New Zealand (0.037/100 000 person-years [95%
CI: 0.036–0.038] and 0.7/100,000 persons [95% CI: 0.66–0.74]). There was
prominent female predominance in adults and the AQP4-Ab–seropositive
subpopulation. The incidence and prevalence peaked in middle-aged adults.
African ethnicity had the highest incidence and prevalence of NMOSD,
whereas White ethnicity had the lowest. No remarkable trend of incidence
was described over time. Conclusion: NMOSD is a rare disease worldwide.
Variations in prevalence and incidence have been described among different
geographic areas and ethnicities. These are only partially explained by
different study methods and NMO/NMOSD definitions, highlighting the need
for specifically designed epidemiologic studies to identify genetic
effects and etiologic factors.