Supplementary Material for: Rural-Urban Differences in Diagnosed Cervical Artery Dissection in New York State

Background: Cervical artery dissection (CeAD) is a leading cause of stroke in young adults. Incidence estimates may be limited by under- or overdiagnosis. Objective: We aimed to investigate if CeAD diagnosis would be higher in urban centers compared to rural regions of New York State (NYS). Methods: For this ecological study, administrative codes were used to identify CeAD discharges in the NYS Statewide Planning and Research Cooperative System (SPARCS) from 2009 to 2014. Rural Urban Commuting Area (RUCA) codes were taken from the US Department of Agriculture and included the classifications metropolitan, micropolitan, small town, and rural. Negative binomial models were used to calculate effect estimates and 95% confidence limits (eβ; 95% CL) for the association between RUCA classification and the number of dissections per ZIP code. Models were further adjusted by population. Results: Population information was obtained from the US Census Bureau on 1,797 NYS ZIP codes (70.7% of NYS ZIP codes), 826 of which had at least 1 CeAD-related discharge from 2009 to 2014. Nonrural ZIP codes were more likely to report more CeAD cases relative to rural areas even after adjusting for population (metropolitan effect = eβ 5.00; 95% CI: 3.75–6.66; micropolitan effect 3.02; 95% CI: 2.16–4.23; small town effect 2.34; 95% CI: 1.58–3.47). Conclusions: CeAD diagnosis correlates with population density as defined by rural-urban status. Our results could be due to underdiagnosis in rural areas or overdiagnosis with increasing urbanicity.