Originally published by 2 Minute Medicine® (view original article). Reused on AccessMedicine with permission.

1. Incidence of optic neuritis remained stable in the UK across 22 years.

2. Participants with optic neuritis demonstrated significantly greater odds of several immune-mediated inflammatory diseases (IMIDs), which, in combination, outnumbered cases of multiple sclerosis.

3. Individuals with optic neuritis had significantly greater hazard ratios for several IMIDs, including multiple sclerosis.

Evidence Rating Level: 2 (Good)

Study Rundown:

Optic neuritis (ON) is the inflammation and subsequent injury of the optic nerve, often considered an early sign of multiple sclerosis (MS). Research on ON is growing but there are limited studies on its incidence and associations with inflammatory diseases. MS is one disease that is often associated with ON but varies tremendously in prevalence. This study conducted in the UK sought to determine associations between ON and systemic and neurologic disease as well as estimate 22-year trends.

This prospective cohort study included 10,937,511 patients from the Health Improvement Network in the UK to investigate ON incidence and its potential association with immune-mediated inflammatory diseases (IMIDs). ON incidence across 22 years in the UK is relatively stable and most frequently associated with MS. However, ON patients had significantly greater odds of multiple prior IMIDs, and were additionally associated with increased hazard of incident IMIDs, predominantly MS. This study provides valuable insight to ON and its associated conditions, as these associated IMIDs outnumber MS-associated ON cases and place eyesight at significant risk.

In-Depth [ prospective cohort]:

This prospective cohort study focused on patients one year or older from January 1, 1995 to September 1, 2019. Annual ON incidence were estimated and sequential cross-sectional studies on data collected at the start of each year allowed for annual ON prevalence estimation. Three years were excluded due to incomplete data (1995, 1996, 2019). Matched case-control and retrospective cohort studies were used with data from the start of 1995 to September 1, 2019 to investigate adjusted odds ratios and hazard ratios (HRs) for 66 IMIDs.

A total of 10,937,511 patients (median [IQR] age at entry = 32.6 [18.0 to 50.4] years; 50.9% female) were included in subsequent analyses. Of these, 2,826 had incident ON (M [SD] age = 35.6 [15.6] years; 69.4% female). Across 22 years, ON incidence was relatively stable at 3.7 per 100,000 person-years (95% CI 3.6 to 3.9). Increasing with database maturity, annual point prevalence rose from 69.3 (95% CI 57.2 to 81.3) in 1997 to 114.8 (95% CI 65.4 to 147.5) in 2018. The highest risk of ON was associated with female sex, reproductive age, smoking, obesity, and residence at higher latitude. ON patients had significantly greater odds of prior syphilis (OR = 5.76, 95% CI 1.39 to 23.96), MS (OR = 98.22, 95% CI 65.40 to 147.52), vasculitis (OR = 3.70, 95% CI 1.68 to 8.15), Mycoplasma (OR = 3.90, 95% CI 1.09 to 13.93), Epstein-Barr virus (OR = 2.29, 95% CI 1.90 to 2.92), sarcoidosis (OR = 2.50, 95% CI 1.21 to 5.18), psoriasis (OR = 1.28, 95% CI 1.03 to 1.58), and Crohn disease (OR = 1.97, 95% CI 1.13 to 3.43). These ON patients also exhibited a higher hazard of incident MS (HR = 284.97; 95% CI 167.85 to 483.81), vasculitis (HR = 4.89, 95% CI 1.82 to 13.10), sarcoidosis (HR = 14.80, 95% CI 4.86 to 45.08), Behçet disease (HR = 17.39, 95% CI 1.55 to 195.53), Sjögren syndrome (HR = 3.48, 95% CI 1.38 to 8.76), and herpetic infection (HR = 1.68, 95% CI 1.24 to 2.28).

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