Trends Over Time in the Incidences of ST-Segment Elevation Myocardial Infarction and Non-ST-Segment Elevation Myocardial Infarction During the Past Decade in a Rural Japanese High-Aged Population

Background: In developed countries, the incidence of non-ST-segment elevation myocardial infarction (NSTEMI) has outpaced that of ST-segment elevation myocardial infarction (STEMI). However, whether this trend is observed in Japan, in which the aging of society is rapidly progressing, remains to be elucidated. Methods and Results: This study retrospectively investigated the trends over time in the incidence of acute coronary syndrome (ACS) between August 2009 and July 2019 at 2 institutions in Izumo City (in rural Japan), which has an elderly population. Crude and age-sex-adjusted incidences of total ACS, STEMI, and non-ST-segment elevation-ACS (NSTE-ACS; including NSTEMI and unstable angina pectoris) were calculated for each year. In the total population, factors associated with the development of NSTEMI were evaluated by multivariate analysis. In total, 1,087 patients were enrolled. The age-adjusted incidence of NSTE-ACS in male patients aged >= 75 years showed a significantly increasing trend. The proportion of NSTEMI per total ACS cases showed a significantly increasing trend over the entire study period. In the multivariate analysis, pre-development use of >= 3 medications for comorbidities was associated with the development of NSTEMI, independent of high-sensitivity cardiac troponin assay use. Conclusions: This study demonstrated an increasing trend in the incidence of NSTEMI in a rural high-aged Japanese population. In addition to the widespread use of high-sensitivity cardiac troponin assays, early medication use for comorbidities might have contributed to this trend.