Factors associated with the time to next attack in neuromyelitis optica: accelerated failure time models with random effects

• Published in: PloS one 2013-12, Vol.8 (12), p.e82325
• Main Authors: Kim, Sung-Min, Park, Junwoo, Kim, Sun Hee, Park, Su-Yeon, Kim, Jee Young, Sung, Jung-Joon, Park, Kyung Seok, Lee, Kwang-Woo
• Format: Article
• Language: English
• Subjects: Adolescent; Adult; Aged; Analysis; Antibodies; Antibodies, Monoclonal, Murine-Derived - therapeutic use; Aquaporin 4; Aquaporin 4 - immunology; Aquaporins; Autoantibodies; Azathioprine; Azathioprine - therapeutic use; Central nervous system; Child; Confidence intervals; Demographics; Demography; Demyelination; Dependent variables; Failure analysis; Female; Frailty; Hospitals; Humans; Immunosuppressive Agents - therapeutic use; Male; Medical prognosis; Medical records; Medical research; Medical treatment; Medicine; Medicine, Experimental; Middle Aged; Models, Theoretical; Monoclonal antibodies; Neurology; Neuromyelitis; Neuromyelitis Optica - diagnosis; Neuromyelitis Optica - drug therapy; Neuromyelitis Optica - immunology; Patients; Prednisolone; Prednisolone - therapeutic use; Recurrence; Retrospective Studies; Risk Factors; Rituximab; Statistical analysis; Statistics; Survival analysis; Time Factors; Treatment Outcome; Viral antibodies; Young Adult
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0082325

Neuromyelitis optica (NMO) is an inflammatory demyelinating disorder of the central nervous system with a relapsing and remitting course. We aimed to identify factors associated with the time to next attack, including the effect of the natural disease course and the diverse treatment regimens, by applying a longitudinal statistical analysis to the individual attacks of each patient. In total, 184 acute attacks among 58 patients with either NMO or NMO spectrum disorder with anti-aquaporin-4 antibody were assessed retrospectively. Patient demographics, clinical characteristics at each attack, and type of treatment during inter-attack periods were assessed. The dependent variable was defined as the time from each attack to the next attack (inter-attack interval). An exponential accelerated failure time model with shared gamma frailty was adapted for statistical analysis. A multivariable analysis revealed that the time from each attack to the next attack in NMO increased independently by 1.31 times (95% confidence interval (CI), 1.02-1.67; p = 0.035) with each additional cumulative attack experienced, by 5.34 times (95% CI, 1.57-18.13; p = 0.007) with combined azathioprine treatment and continued oral prednisolone, and by 4.26 times (95% CI, 1.09-16.61; p = 0.037) with rituximab treatment. The time to next attack in NMO can increase naturally in the later stages of the disease as the number of cumulative attacks increases. Nevertheless, both combined azathioprine treatment with continued oral prednisolone and rituximab treatment were also associated with a longer time to next attack, independently of the natural disease course of NMO.