Glucosamine Use and Risk of First-Ever Optic Neuritis: A Nationwide 16-Year Longitudinal Analysis

Introduction: Evidence of neuroprotective effects of glucosamine on Asian optic neuritis (ON) patients remains sparse. We aimed to examine the longitudinal association between glucosamine use and the incidence of first-ever ON to identify the factors contributing to reducing ON risk in older Asian populations. Methods: This nationwide cohort study from 2000 to 2015 evaluated 24,155 individuals. The International Classification of Diseases-9 Clinical Modification code 377 determined newly diagnosed ON. Outcomes include the annual trend of first-ever ON incidence, crude/adjusted hazard ratios (HRs) of incident ON stratified by sociodemographic characteristics, and comorbidities. Results: Glucosamine exposure has been significantly associated with reduced ON incidence (Log-rank p < 0.001) since the fifth year of clinical surveillance. The overall adjusted HR of ON among glucosamine users was 0.718 (CI = 0.524-0.901, p = 0.001), and in the glucosamine-exposed group, disease onset was approximately 129 days later than in nonusers (6.83 +/- 4.27 vs. 6.47 +/- 4.01 years to ON, p < 0.001). Moreover, glucosamine was associated with reduced ON risk in patients without diabetes mellitus, hypertension, tobacco use, and chronic heart failure. While administering glucosamine, the risk was reduced by more than half among individuals aged between 45 and 64 years (aHR = 0.433, CI = 0.316-0.544, p < 0.001) and patients from medical centers (aHR = 0.453, CI = 0.330-0.568, p < 0.001). Conclusion: Taiwanese glucosamine users have a decreased risk of developing ON. Our work provides a theoretical basis for expanding glucosamine indications in regions with minimal prevalence of ON.