Detecting Seasonal Trends in Occurrence of Demyelinating Optic Neuritis within the Ottawa Region
Authors: Deeksha Kundapur, Noran Badeeb, Danah Albreiki.
Author Disclosure Block: D. Kundapur: None. N. Badeeb: None. D. Albreiki: None.
Purpose: Some of the most common associations of demyelinating optic neuritis (ON) include multiple sclerosis related (MS-ON), neuromyelitis optica (NMO), myelin oligodendrocyte glycoprotein ON (MOG-ON), and idiopathic ON. The onset of ON in a population demonstrates some degree of seasonal variation, which has been observed across a limited number of studies. This variation is inconsistent between studies, possibly due to differences in geographic, demographic and environmental factors, as well as long-term shifts in trends. Determining seasonal patterns underlying onset of ON may provide valuable epidemiological information and help delineate causative or protective factors for recurrence.
Study Design: Single-center retrospective chart review. Methods: 1402 patient charts were identified using diagnostic codes via a database search (01/01/2010-31/03/2021) of the EPIC EMR used at the Ottawa Eye Institute. Charts were reviewed for documentation supporting a diagnosis of ON falling into the following categories: MS-ON, MOG-ON, NMO, or idiopathic-ON. Other causes of ON were excluded. Date of onset, biological sex, and age were extracted from each chart and stored per ethics guidelines. Data was analyzed using SAS statistical software for calculation of the following: frequency by season (defined as 3-month blocks starting in December) and category, and overall pooled seasonal trends of all cases of ON. The MS-ON category included clinically isolated syndrome (CIS) with positive MRI findings given the high likelihood of progression to MS.
Results: Of 1402 charts screened, 218 charts were included in the study sample. Data analysis revealed the following: overall seasonal trend was non-significant but was lowest in winter and spring (22% and 23%, respectively) and highest in summer and fall (28% and 27% respective). Divided further, MS-ON (n=144) rates were lowest in the spring (21%) and highest in fall (29%); MOG-ON (n=25) rates were lowest in winter (16%) and highest in summer and fall (both at 32%); NMO (n=16) rates were lowest in fall (12.5%) and highest in winter and summer (both at 31.25%); idiopathic-ON (n=33) rates were lowest in fall (18%) and highest in spring (33%).
Conclusions: The overall ON seasonal trend appears to have a predilection for the summer and fall months, which is in keeping with some literature citing warmer weather and viral infections as risk factors for MS relapse during those seasons. The largest group (MS-ON) demonstrated a peak in the fall.