Regional Disparities in Hyperacute Treatment and Functional Outcomes after Acute Ischemic Stroke in Japan

Abstract

BackgroundAcute ischemic stroke (AIS) is a major health challenge affecting approximately 15 million people globally each year, of whom 5 million die and another 5 million are permanently disabled, imposing major burdens on families and society 1,2) . The incidence, treatment, and outcomes of AIS can vary based on a broad range of social factors, making it a multifaceted issue that transcends medical and healthcare boundaries. In North America and China, AIS mortality is reportedly higher in remote and rural areas than in urban areas; however, the reasons for this disparity are not well understood [3][4][5][6] . Factors hypothesized to explain this observation include a higher AIS incidence, uneven distribution of Aim: This study investigated the impact of rurality on acute ischemic stroke (AIS) outcomes, emphasizing the hyperacute phase, in which immediate care is crucial. Methods: This retrospective cohort study analyzed data from a large Japanese hospital network covering AIS patients from 2013-2021, was analyzed. The focus was on patients admitted within 4.5 h of the onset, using the Rurality Index for Japan (RIJ) to categorize patients into rural or urban groups. This study examined treatment methods (intravenous thrombolysis [IVT] and mechanical thrombectomy [MT]) and functional outcomes measured using the modified Rankin Scale (mRS), where scores of 3-6 indicated poor outcomes. Multilevel logistic regression was used to calculate the adjusted odds ratios (ORs) and 95% confidence intervals (CIs) for poor outcomes based on rurality. The study also evaluated the population-attributable fraction (PAF) to estimate potential outcome improvements in urban settings. Results: Of 27,691 patients, 17,516 were included in the total cohort and 4,954 in the hyperacute cohort. Urban patients constituted 73.7% (12,902), with higher IVT (5.2%) and MT (3.6%) rates than rural patients (4.1% IVT, 2.0% MT). Poor mRS outcomes were more common in rural areas than in urban areas, with adjusted ORs of 1.30 (1.18-1.43) in the total cohort and 1.43 (1.19-1.70) in the hyperacute cohort. The PAF for poor outcomes due to rural residency was 14.8% (0.5%-31.0%). Conclusion:This study demonstrated a notable association between rurality and poorer AIS outcomes in Japan, particularly in the hyperacute phase.