Abstract WMP62: Stroke Severity Is The Primary Mediator Of Increased Stroke Mortality In The Elderly

Abstract

Background: The risk of ischemic stroke mortality increases with age, but the impact of stroke severity on this relationship has not been fully examined. Methods: We included adults in the National Inpatient Sample from 2016-2019 who had a primary discharge diagnosis of ischemic stroke (I63*) and a baseline NIH Stroke Scale (NIHSS). The primary outcome was in-hospital death. The exposure of age had left skew, so we transformed it into deciles. We fit a logistic regression model adjusted for sex, race/ethnicity, diabetes, atrial fibrillation, hypertension, thrombolytic therapy, and endovascular therapy. We report the predicted probability of the primary outcome with and without NIHSS and use structural equation modeling (SEM) to estimate the proportion of age’s effect on the primary outcome that is mediated by stroke severity. Results: We included 138,637 individuals, of which 3.5% died in-hospital. The proportion of in-hospital death and an NIHSS violinplot by decile of age are seen in Figure 1, both of which had a positive linear relationship. The AUC of the multivariable model without NIHSS was 0.70 and with NIHSS was 0.86 (p<0.001). The predicted probability of death is seen without and with NIHSS in Figure 2, illustrating the importance of adjusting for NIHSS. In the SEM model, we observed that 57.7% of age’s effect on in-hospital death is mediated by stroke severity. Conclusions: We found that elderly individuals in the United States have more severe stroke and higher stroke mortality, but the effect of age on stroke mortality is primarily mediated by elderly individuals having more severe stroke. Additional research is needed to better understand this novel finding.