Increased Risk of Optic Neuritis in Patients With Fibromyalgia: Nationwide Population-Based Cohort Study in South Korea.

Purpose: To estimate the risk of incidence of optic neuritis and identify the high-risk group among patients with fibromyalgia (FM).

Design: Population-based cohort study.

Methods: A nationwide, population-based study was conducted using data from the Korean National Health Claims database from 2012 to 2021. This study included all the patients with FM from the entire South Korean population aged 20-79 years (FM group). Moreover, those with pain but not diagnosed with FM were considered as the non-FM group. A cohort was established by classifying it into the FM and non-FM groups during the recruitment period. A log-rank analysis was used to compare the risk of optic neuritis incidence between the FM group and non-FM group. Cox proportional hazards regression analysis was performed to calculate the adjusted hazard ratio (HR). The cohort was analyzed by stratifying according to age and sex.

Results: The FM and non-FM groups included 479,892 and 479,892 participants, respectively. The incidence rate of optic neuritis was 35.65/100,000 person-years in the FM group; the HR was significantly higher in the FM group than in the non-FM group (HR 2.11, 95% CI 1.84-2.41; P < .001). The mean interval between the onset of FM and incident optic neuritis was 2.4 ± 1.8 years. The risk increased significantly in men aged 60-79 years (HR 3.37, 95% CI 2.54-4.48) and in women aged 20-39 years (HR 2.07, 95% CI 1.38-3.22).

Conclusion: We quantified the risk of optic neuritis through a long-term follow-up, which could contribute to understanding the pathophysiology and estimating the general health care burden associated with FM in a practical setting. Great attention should be paid to its risk in older men and younger women.