Epidemiology of neuromyelitis optica spectrum disorder in Denmark (1998-2008, 2007-2014)

Sex ratio and age of onset in AQP4 antibody-associated NMOSD: a review and meta-analysis

BACKGROUND

Aquaporin-4 (AQP4) antibody-associated neuromyelitis optica spectrum disorder (NMOSD) is an antibody-mediated inflammatory disease of the central nervous system. We have undertaken a systematic review and meta-analysis to ascertain the sex ratio and mean age of onset for AQP4 antibody associated NMOSD. We have also explored factors that impact on these demographic data.

METHODS

A systematic search of databases was conducted according to the PRISMA guidelines. Articles reporting sex distribution and age of onset for AQP4 antibody-associated NMSOD were reviewed. An initially inclusive approach involving exploration with regression meta-analysis was followed by an analysis of just AQP4 antibody positive cases.

RESULTS

A total of 528 articles were screened to yield 89 articles covering 19,415 individuals from 88 population samples. The female:male sex ratio was significantly influenced by the proportion of AQP4 antibody positive cases in the samples studied (p < 0.001). For AQP4 antibody-positive cases the overall estimate of the sex ratio was 8.89 (95% CI 7.78-10.15). For paediatric populations the estimate was 5.68 (95% CI 4.01-8.03) and for late-onset cases, it was 5.48 (95% CI 4.10-7.33). The mean age of onset was significantly associated with the mean life expectancy of the population sampled (p < 0.001). The mean age of onset for AQP4 antibody-positive cases in long-lived populations was 41.7 years versus 33.3 years in the remainder.

CONCLUSIONS

The female:male sex ratio and the mean age of onset of AQP4 antibody-associated NMOSD are significantly higher than MS. The sex ratio increases with the proportion of cases that are positive for AQP4 antibodies and the mean age of onset increases with population life expectancy.

Comparative study of AQP4 antibody-related diseases and MOG antibody-related diseases among the population in Hunan, China

To compare the clinical, imaging, and prognostic characteristics of AQP4 antibody-related diseases and MOG antibody-related diseases. The clinical data of 56 AQP4 antibody-positive patients and 14 MOG antibody-positive patients in the Second Xiangya Hospital of Central South University from June 2016 to June 2019 were collected. 92.9% of the patients with positive AQP4 antibody were females and 64.3% of patients with positive MOG antibody were females (P = 0.004). Patients with positive AQP4 antibody were more likely to have limb movement (P < 0.001) or limb sensory dysfunction (P < 0.001), and were more likely to have limb twitching (P = 0.036). In addition, AQP4 antibody-positive patients were more likely to have positive ANA (P = 0.013) and SSA antibody (P = 0.029), Ro-52 antibody (P = 0.047), immunoglobulin (P = 0.007), thyroid antibody (P = 0.007), abnormal C3 (P = 0.011), abnormal C4 (P = 0.014) than MOG antibody-positive patients. The involvement rate of head in MOG antibody-positive patients was higher than AQP4 antibody-positive patients (P = 0.029). The severity of clinical symptoms in AQP4-positive patients was usually more serious than that in MOG-positive patients (P < 0.001). The residual neurological deficit after treatment in AQP4-positive group was usually more serious than that in MOG-positive group (P < 0.001). AQP4 antibody-positive patients had a higher prevalence in women than MOG antibody-positive patients, and AQP4 antibody-positive patients were more likely to have spinal cord involvement symptoms and connective tissue antibody abnormalities. The EDSS score of them were higher than that of MOG antibody-positive patients after treatment, and the prognosis was worse.

[Epidemiology of neuromyelitis optica spectrum disorder]

Neuromyelitis optica spectrum disorder (NMOSD) is a group of rare and mostly severe autoimmune demyelinating central nervous system disorders which prevalence is 0.7-1 per 100.000 population and incidence is 0.037-0.73 per 100.000 person-years. NMOSD may present as a combination of uni- or bilateral optic neuritis, transverse myelitis or lesions of brain stem and other brain regions. The symptoms are mostly relapsing (up to 97.5%) and progressive. Occurrence of relapses is associated with seropositivity for aquaporin-4 (up to 80% of NMOSD patients) and bears a less favorable prognosis (mortality up to 32%). Women seropositive for aquaporin 4 constitute 90% of NMOSD patients. Compared to other demyelinating disorders, NMOSD is characterized by late onset (mean age is about 39 years) and association with other autoimmune disorders, including systemic lupus erythematosus, myasthenia gravis and Sjogren's syndrome. A genetic predisposition was found among Blacks and Asians, with HLA-DRB1*03:01 gene associated with higher risk of NMOSD in Asians. The course of the disease tends to be more severe in Blacks. There are clusters of an increased incidence of NMOSD in the Carribeans and in the Far East. Continued increase of prevalence and incidence of NMOSD worldwide compels continued epidemiological research in order to provide early diagnosis and treatment for this disorder.

Neuromyelitis Optica Spectrum Disorder: Clinical Burden and Cost of Relapses and Disease-Related Care in US Clinical Practice

Introduction

Neuromyelitis optica spectrum disorder (NMOSD) is a rare autoimmune condition characterized by unpredictable relapses that affect the optic nerves and spinal cord, which can lead to blindness, paralysis, and increased mortality rates. Evidence on the clinical and economic burden of NMOSD in the USA is currently lacking.

Methods

A retrospective, observational cohort study was conducted using data from the IQVIA PharMetrics Plus Healthcare Claims Database between January 1, 2012 and March 31, 2019. Adults (aged 18 years or more) with evidence of NMOSD and a matched group of comparison patients were identified. Outcomes, including NMOSD relapses, healthcare utilization, and healthcare expenditure (reported in 2018 US dollars), were evaluated during the follow-up period (maximum 6 years). Healthcare utilization and expenditure were assessed overall (all-cause) and during NMOSD relapses.

Results

The study included 1363 patients with NMOSD; the mean age was 44.9 years, and 75.3% were female. During the follow-up period (median 2.0 years), 47.7% of patients with NMOSD had one or more relapses, corresponding to an annualized relapse rate of 0.8 (95% confidence interval [CI] 0.7–0.9). When analyzing healthcare expenditure per patient, the mean annualized all-cause healthcare expenditure among patients with NMOSD was $60,599 (95% CI $52,112–66,716) compared with $8912 (95% CI $7084–10,727) among comparison patients, representing a difference of $51,687 (95% CI $43,820–58,664) attributable to NMOSD. The mean annualized total expenditure for NMOSD relapses was $10,070 (95% CI $7726–12,660) per patient, with hospital/inpatient care requiring more expenditure than ambulatory/outpatient care.

Conclusion

Findings of this large, retrospective, observational study indicate that relapses among patients with NMOSD are common in US clinical practice, leading to substantial healthcare utilization and expenditure. Therapies with the highest relapse risk reduction could lead to markedly lower relapse-associated healthcare utilization and clinical burden in patients with NMOSD.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40120-021-00253-4.

Neuromyelitis optica spectrum disorder (NMOSD) is a severely debilitating neurological disease that affects the nerves in the brain and spinal cord. People who have NMOSD may experience recurrent attacks, or relapses, that can cause blindness and disability. These relapses may lead to hospitalizations, doctor’s office visits, and pharmacy costs that are paid by health insurance plans. Overall, the cost of treating relapses in patients with NMOSD is substantial. Our study analyzed healthcare claims data from the USA. During a median follow-up time of 2.0 years, our study showed that 47.7% of patients with NMOSD experienced one or more relapses, resulting in hospital/inpatient admissions and ambulatory/outpatient treatments. In addition, the average healthcare cost among patients with NMOSD was $60,599 per year compared with $8912 per year for patients without NMOSD. This represents a difference of $51,687 per year, which can be attributed to NMOSD. Among patients with three or more relapses during the follow-up period, the average total healthcare cost was more than $83,000 per patient. Therefore, medicines that prevent relapses could lead to fewer relapse-associated hospitalizations and outpatient treatments for patients with NMOSD.

Anti-aquaporin 4 IgG Is Not Associated With Any Clinical Disease Characteristics in Neuromyelitis Optica Spectrum Disorder

Background: Neuromyelitis optica spectrum disorder (NMOSD) is a clinically defined, inflammatory central nervous system (CNS) disease of unknown cause, associated with humoral autoimmune findings such as anti-aquaporin 4 (AQP4)-IgG. Recent clinical trials showed a benefit of anti-B cell and anti-complement-antibodies in NMOSD, suggesting relevance of anti-AQP4-IgG in disease pathogenesis. Objective: AQP4-IgG in NMOSD is clearly defined, yet up to 40% of the patients are negative for AQP4-IgG. This may indicate that AQP4-IgG is not disease-driving in NMOSD or defines a distinct patient endotype. Methods: We established a biobank of 63 clinically well-characterized NMOSD patients with an extensive annotation of 351 symptoms, patient characteristics, laboratory results and clinical scores. We used phylogenetic clustering, heatmaps, principal component and longitudinal causal interference analyses to test for the relevance of anti-AQP4-IgG. Results: Anti-AQP4-IgG was undetectable in 29 (46%) of the 63 NMOSD patients. Within anti-AQP4-IgG-positive patients, anti-AQP4-IgG titers did not correlate with clinical disease activity. Comparing anti-AQP4-IgG-positive vs. -negative patients did not delineate any clinically defined subgroup. However, anti-AQP4-IgG positive patients had a significantly (p = 0.022) higher rate of additional autoimmune diagnoses. Conclusion: Our results challenge the assumption that anti-AQP4-IgG alone plays a disease-driving role in NMOSD. Anti-AQP4-IgG might represent an epiphenomenon associated with NMOSD, may represent one of several immune mechanisms that collectively contribute to the pathogenesis of this disease or indeed, anti-AQP4-IgG might be the relevant factor in only a subgroup of patients.

Urban prevalence of multiple sclerosis in China: A population-based study in six provinces

BACKGROUND AND PURPOSE

Multiple sclerosis (MS) is a rare neurological disease addressed by only few epidemiological studies in China. This population-based study aimed to estimate the prevalence of MS in China by using national medical insurance databases.

METHODS

Data from the Urban Employee Basic Medical Insurance database and the Urban Residence Basic Medical Insurance database, which were collected during 2012 to 2016 and included approximately 0.20 billion residents in six provinces, were used in this population-based study. The prevalent patients with MS were identified via diagnostic text or disease codes.

RESULTS

The crude prevalence in 2016 was 2.44 per 100,000 population (95% confidence interval (CI) 2.18-2.72), with the prevalence in females being higher than that in males. The standardized prevalence (based on 2010 Chinese census data) was 2.29 (95% CI 2.21-2.38). The prevalence in both sexes in 2016 increased up to the age range of 30-34 years. Subsequently, the female prevalence declined with increasing age, but male prevalence stabilized with increasing age. During the 5-year time period, prevalence ranged from 2.32 (95% CI 2.06-2.60) in 2015 to 2.91 (95% CI 2.39-3.47) in 2012.

CONCLUSIONS

The prevalence of MS in China was lower than that in Europe and North America. The temporal trend of prevalence in China was also observed to be stable. As the first prevalence study of MS in mainland China, this population-based study can provide useful information for worldwide healthcare services and prevention of MS.

Worldwide Incidence and Prevalence of Neuromyelitis Optica: 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.

Epidemiology of Neuromyelitis Optica Spectrum Disorder and Its Prevalence and Incidence Worldwide

Neuromyelitis optica spectrum disorder (NMOSD) is an uncommon inflammatory disease of the central nervous system, manifesting clinically as optic neuritis, myelitis, and certain brain and brainstem syndromes. Cases clinically diagnosed as NMOSD may include aquaporin 4 (AQP4)-antibody-seropositive autoimmune astrocytopathic disease, myelin oligodendrocyte glycoprotein (MOG)-antibody-seropositive inflammatory demyelinating disease, and double-seronegative disease. AQP4-antibody disease has a high female-to-male ratio (up to 9:1), and its mean age at onset of ~40 years is later than that seen in multiple sclerosis. For MOG-antibody disease, its gender ratio is closer to 1:1, and it is more common in children than in adults. Its clinical phenotypes differ but overlap with those of AQP4-antibody disease and include acute disseminated encephalomyelitis, brainstem and cerebral cortical encephalitis, as well as optic neuritis and myelitis. Double-seronegative disease requires further research and clarification. Population-based studies over the past two decades report the prevalence and incidence of NMOSD in different populations worldwide. One relevant finding is the varying prevalence observed in different racial groups. Consistently, the prevalence of NMOSD among Whites is ~1/100,000 population, with an annual incidence of <1/million population. Among East Asians, the prevalence is higher, at ~3.5/100,000 population, while the prevalence in Blacks may be up to 10/100,000 population. For MOG-antibody disease, hospital-based studies largely do not observe any significant racial preponderance so far. This disorder comprises a significant proportion of NMOSD cases that are AQP4-antibody-seronegative. A recent Dutch nationwide study reported the annual incidence of MOG-antibody disease as 1.6/million population (adult: 1.3/million, children: 3.1/million). Clinical and radiological differences between AQP4-antibody and MOG-antibody associated diseases have led to interest in the revisions of NMOSD definition and expanded stratification based on detection of a specific autoantibody biomarker. More population-based studies in different geographical regions and racial groups will be useful to further inform the prevalence and incidence of NMOSD and their antibody-specific subgroups. Accessibility to AQP4-antibody and MOG-antibody testing, which is limited in many centers, is a challenge to overcome. Environmental and genetic studies will be useful accompaniments to identify other potential pathogenetic factors and specific biomarkers in NMOSD.

Pre-pregnancy, obstetric and delivery status in women with neuromyelitis optica spectrum disorder

BACKGROUND

Neuromyelitis optica spectrum disorder (NMOSD) is a potentially disabling disease which affects predominantly women of reproductive age.

OBJECTIVES

To evaluate the pre-pregnancy condition and to investigate the prevalence of obstetrical and neonatal complaints in NMOSD.

METHODS

An observational retrospective study of 37 NMOSD patients positive for aquaporin-4-immunoglobulin-IgG. Age at menarche, menstrual cycle, gravidity, type of delivery obstetrical complications and perinatal problems were recorded. We assessed the annualized relapse rate (ARR).

RESULTS

A total of 23 patients (62%) suffered from irregular menstruations and two from infertility after disease onset. 11 patients had 20 informative pregnancies with 14 deliveries (5 cesareans) and six abortions, four spontaneous, and two ectopic pregnancies after the first trimester. Additionally, three patients experienced threatening abortion and one preeclampsia. No stillbirth or premature birth was recorded. None of the patients experienced attacks during pregnancy, but postpartum relapses occurred after 10 deliveries (71,4%) with the highest ARR (0.937; p = 0.037) during the first three months postpartum compared to pre-pregnancy ARR (0.375). Four patients (10.8%) developed the initial symptoms of NMOSD postpartum.

CONCLUSION

Irregular menstruation in more than half of NMOSD patients may reflect a hormonal imbalance. Pregnancies were associated with obstetrical complications and increased disease activity postpartum.

Epidemiology of neuromyelitis optica spectrum disorder in Denmark (1998-2008, 2007-2014)

Epidemiological studies of the uncommon disorder neuromyelitis optica spectrum disorder (NMOSD) may be difficult to interpret because of the evolving nature of diagnostic criteria, differences in the definition and accuracy of NMOSD diagnosis, the completeness of case ascertainment, and variability in assays for the disease-specific biomarker aquaporin-4 (AQP4)-IgG. A sub-group of patients with the clinical syndrome NMOSD lack detectable AQP4-IgG and in these cases an accurate diagnosis requires precise diagnostic algorithms and longitudinal follow-up. Consecutive sets of criteria for NMO/NMOSD have been introduced during the two last decades. Such criteria need validation in different populations. Detection of other autoantibodies, such as IgG specific for myelin oligodendrocyte glycoprotein or for glial fibrillary acidic protein in a sub-group of AQP4-IgG-negative NMOSD patients, has improved over the past decade and may lead to overlap of the clinical syndromes/phenotypes. This review begins by summarizing current knowledge on the widening clinical spectrum of NMOSD. Subsequently, we describe two epidemiological studies from Denmark carried out in two different decades (1998-2008 and 2007-2014) and comment on the differences in study design, patient ascertainment, and interpretation of results. These factors may explain some of the observed differences, reflecting the complexity and providing a clear example of this development.