Objective: This study aimed to investigate recent nationwide trends in the epidemiology of acute ischemic stroke (AIS) in Japan.
Methods: We analyzed 328,147 acute ischemic stroke patients in 350 certified training hospitals in Japan using data obtained from the Japanese Diagnosis Procedure Combination Database. Data between the period April 1, 2010 and May 31, 2014 were used. We divided patients into three treatment groups: medical treatment only (group M), intravenous t-PA infusion only (group IVT), and endovascular treatment (group ET). Outcome was assessed by in-hospital mortality and modified Rankin Scale (mRS) score at discharge, and poor outcome was defined as a mRS score of 3-6.
Results: The patient proportion in groups M, IVT, and ET changed from 94.3%, 3.2%, and 1.6% in 2010 to 90.9%, 4.3%, and 3.7% in 2014, respectively (P<0.0001). In all AIS patients, in-hospital mortality significantly decreased from 6.5% in 2010 to 5.3% in 2014 (p<0.0001) and poor outcome at discharge also decreased from 42.7% in 2010 to 41.6% in 2014 (p<0.0001). In groups M and IVT, in-hospital mortality significantly decreased from 6.3% and 12.0% in 2010 to 5.0% and 9.1% in 2014, respectively (p<0.0001), and poor outcome at discharge also decreased from 42.1% and 60.7% in 2010 to 40.7% (P<0.0001) and 55.4% (p<0.005) in 2014, respectively. In contrast, in group ET, both in-hospital mortality (from 11% in 2010 to 9.5% in 2014) and poor outcome at discharge (from 53.4% in 2010 to 54.0% in 2014) were not significantly different between the two time points.
Conclusion: In Japan, during the 5-year period before the guidelines concerning proper use of ET for AIS were revised in 2015, a significant improvement in in-hospital mortality and functional outcomes of AIS patients undergoing medical treatment and intravenous rt-PA infusion was observed. This was probably due to a gradual increase in the proportion of patients undergoing IVT; the outcomes of ET, however, remained the same.