Association of Demographic, Clinical, and Environmental Factors With Disease Severity in Adult Myasthenia Gravis: A Multicenter Cross-Sectional Study.

BACKGROUND

The severity of myasthenia gravis (MG) varies significantly among individuals, yet the factors underlying this heterogeneity are not fully understood. This study aimed to investigate the association between demographic, clinical, and environmental factors and the severity of MG.

METHODS

From February 2017 to December 2021, adult patients registered in the national MG database were enrolled in this cross-sectional study. Baseline data on demographic, clinical, and environmental factors (including the natural environment, socioeconomic status, and lifestyle) were collected. Disease severity was classified as mild or moderate to severe using the MG Activities of Daily Living (MG-ADL) scale and the Quantitative MG (QMG) scale. Logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for these associations.

RESULTS

A total of 2468 patients were included. The median MG-ADL score was 3.0 (interquartile range [IQR] 1.0-6.0), and the median QMG score was 6.0 (IQR 3.0-9.0). Higher MG-ADL scores were associated with age at onset ≥ 65 years (OR 1.85, 95% CI 1.32-2.58), underweight (2.03, 1.35-3.06), generalized onset (2.80, 2.26-3.48), and thymoma (1.70, 1.26-2.30). In contrast, overweight or obesity (OR 0.65, 95% CI 0.52-0.82), medium altitudes (0.64, 0.46-0.90), high educational attainment (0.68, 0.49-0.94), and high monthly household income (0.71, 0.53-0.96) were inversely associated with MG-ADL scores. Factors associated with higher QMG scores included female sex (OR 1.75, 95% CI 1.28-2.37), age at onset ≥ 65 years (1.91, 1.35-2.71), generalized onset (2.50, 2.00-3.13), thymoma (1.97, 1.43-2.71), medium latitudes (1.53, 1.08-2.16), and high altitudes (1.65, 1.10-2.47). Lower QMG scores were correlated with overweight or obesity (OR 0.78, 95% CI 0.61-0.99), thymectomy (0.57, 0.40-0.81), medium altitudes (0.70, 0.49-0.99), and medium sunlight duration (0.67, 0.49-0.93), as well as higher concentrations of particulate matter with an aerodynamic diameter of ≤ 2.5 μm and higher household income.

CONCLUSION

In addition to demographic and clinical factors, environmental factors may also influence MG severity. Further research is warranted to clarify these associations and their underlying mechanisms.