Editors' note: Epidemiology of NMOSD in Sweden from 1987 to 2013: A nationwide population-based study

Field: Medicine (Health Sciences)

In their retrospective observational cohort study of 294 patients with neuromyelitis optica spectrum disorder (NMOSD), Drs. Jonsson et al. summarized the rising incidence rate of this condition in Sweden between 1987 and 2013. The investigators postulate that the higher incidence rate—0.79 per 1,000,000 person-years from 0.30 per 1,000,000 person-years—may have been attributed, in part, to heightened awareness of the disease and greater availability of MRI and NMO antibody testing. These incidence estimates mirror what have been reported in other predominantly Caucasian cohorts. In response, Drs. Papp et al. reiterate that although incidence and prevalence estimates are similar between nations of similar ethnic profiles, Southern Denmark has reported some of the highest prevalence (4.4 per 100,000 person-years) and incidence rates (4.0 per 1,000,000 person-years). Drs. Jonsson et al. comment that the higher estimates reported by Asgari et al. from Southern Denmark may be partially explained by the prospective nature of their study and the fact that patients from that study were evaluated for NMOSD even if optic neuritis was the presenting symptom. Based on the collective results from these studies, it is likely that NMOSD remains an underrecognized condition, and physicians should have a lower threshold to evaluate these patients with serum antibody testing and MRI, given the treatment considerations that are specific to NMOSD compared with MS. A correction to figure 5 was published in the September 10, 2019, issue of Neurology. In their retrospective observational cohort study of 294 patients with neuromyelitis optica spectrum disorder (NMOSD), Drs. Jonsson et al. summarized the rising incidence rate of this condition in Sweden between 1987 and 2013. The investigators postulate that the higher incidence rate—0.79 per 1,000,000 person-years from 0.30 per 1,000,000 person-years—may have been attributed, in part, to heightened awareness of the disease and greater availability of MRI and NMO antibody testing. These incidence estimates mirror what have been reported in other predominantly Caucasian cohorts. In response, Drs. Papp et al. reiterate that although incidence and prevalence estimates are similar between nations of similar ethnic profiles, Southern Denmark has reported some of the highest prevalence (4.4 per 100,000 person-years) and incidence rates (4.0 per 1,000,000 person-years). Drs. Jonsson et al. comment that the higher estimates reported by Asgari et al. from Southern Denmark may be partially explained by the prospective nature of their study and the fact that patients from that study were evaluated for NMOSD even if optic neuritis was the presenting symptom. Based on the collective results from these studies, it is likely that NMOSD remains an underrecognized condition, and physicians should have a lower threshold to evaluate these patients with serum antibody testing and MRI, given the treatment considerations that are specific to NMOSD compared with MS. A correction to figure 5 was published in the September 10, 2019, issue of Neurology.