Impact of comorbidities on relapsing rates of Neuromyelitis Optica Spectrum Disorders: Insights from a longitudinal study in Taiwan

Background : Neuromyelitis optica spectrum disorder (NMOSD) is an autoimmune inflammatory demyelinating disease characterized by relapsing clinical episodes and the presence of autoantibodies. The impact of comorbidities on relapsing rate of NMOSD patients in Taiwan remains unclear. Methods : We conducted a longitudinal retrospective study using the largest hospital system in Taiwan from 2006-2021. Demographic characteristics, annualized relapse rates (ARR), and comorbidities were examined. Results : We identified 485 NMOSD patients from 2006 to 2021. Of these, 466 had the adult form and 19 (3.9%) had the pediatric form of NMOSD. The median ARR was 0.51 (interquartile range (IQR): 0.26-1.11) for adults and 0.39 (IQR: 0.21-0.77) for pediatric patients. Comorbidities included malignancy (6.7%) and autoimmune diseases (21.7%). The recommended age for malignancy surveillance in NMOSD patients was 43.3 years. Neither malignancy nor autoimmune disease increased the ARR within 3 years post diagnosis in NMOSD patients with comorbidities compared with those without comorbidities. Conclusions : Our study revealed the ARR within the initial three years after diagnosis was significantly higher, emphasizing the importance of early treatment. We also observed an association between malignancy and NMOSD, and a significantly higher risk of malignancy in adult patients with NMOSD than in the general population (the relative risk was 5.99) that requiring further investigations into the underlying mechanisms. These findings contribute to a better understanding of NMOSD and its comorbidities in Taiwan.