The risk for bone fractures was increased among patients with neuromyelitis optica spectrum disorder with aquaporin-4 immunoglobulin G antibodies (NMOSD-AQP4), according to study results published in Multiple Sclerosis and Related Disorders.
As limited data are available on the bone health of patients with NMOSD-AQP4, the goal of the current study was to investigate the fracture risk and bone loss in these patients, compared to healthy controls and patients with multiple sclerosis (MS).
The study cohort included 71 patients with NMOSD-AQP4 from 2 major centers in Korea. The researchers matched 3 healthy controls to each case of NMOSD-AQP4; thus a total of 213 healthy controls that took part in the nationwide population-based health and nutritional status survey of Korea were included in the current study. In addition, 41 patients with MS were included as MS controls.
Demographic and clinical data related to bone health was collected, including bone mineral density (BMD) and fracture risk assessment tool (FRAX) score.
Patients with NMOSD-AQP4 had a higher prevalence of fractures after disease onset (17 patients, 23.9%), compared to the healthy controls (7 patients, 3.3%, P <.001), but not compared to MS controls (6 patients, 14.6%, P =.332). The risk for fracture was more than 5-fold higher among those with NMOSD-AQP4, compared to healthy controls (odds ratio 5.40, 95% CI, 2.004-14.524, P =.001). The standardized BMDs of the femoral neck and total hip were also significantly lower in patients with NMOSD-AQP4, compared to healthy controls (P =.044 and P <.001, respectively). The low BMD was more prominent in young patients with NMOSD-AQP4.
There was no significant difference in the prevalence of fractures between the NMOSD-AQP4 and MS groups. However, patients with NMOSD-AQP4 had a higher risk for major osteoporotic fractures as measured by the FRAX (P =.042).
Multivariable binary logistic regression analysis showed that history of falls, and not the use of corticosteroids, was the only significant risk factor for fractures after NMOSD-AQP4 diagnosis (adjusted odds ratio 24.902; 95% CI, 3.086-200.947). Total hip and femoral neck BMD were negatively associated with age and cumulative dose of oral corticosteroids. Sex and prophylactic calcium supplementation were associated with BMD of the femoral neck. BMD at the lumbar spine was negatively associated with menopause.
The study had several limitations, according to the researchers, including the cross-sectional design, data based on self-report questionnaires, limited sample of patients with MS, and limitations secondary to using both Lunar and Hologic bone densitometer to assess BMD.
“Patients with NMOSD-AQP4 had a significantly higher risk of fractures that could mostly be attributed to falling. Additionally, low BMD was observed in these patients; it was more prominent among young patients, associated with steroid use, and may partially prevented by the use of prophylactic calcium supplements,” concluded the researchers.
Kwon YN, Im SY, Park YS, et al. Bone health in neuromyelitis optica: bone mineral density and fractures (published online 28 April, 2020). Mult Scler Relat Disord. Doi: 10.1016/j.msard.2020.102080