Secular trends in the incidence, risk factors, and prognosis of transient ischemic attack in Japan: The Hisayama Study

Abstract

Background and aimsWe aimed to investigate secular trends in the incidence, risk factors, and prognosis of transient ischemic attack (TIA) in a general Japanese population. MethodsTwo cohorts consisting of stroke-free Japanese individuals aged ≥40 years in 1961 (n = 1621) and 1988 (n = 2646) were followed up for 24 years. The associations of potential risk factors with the development of TIA were estimated by a Cox proportional hazards model. The influence of TIA on the risk of total stroke over the subsequent 10 years was compared between the sub-cohorts of subjects with TIA and age- and sex-matched control subjects from each cohort. ResultsDuring follow-up, 28 subjects in the 1961 cohort and 34 in the 1988 cohort experienced TIA. The age-standardized incidence of TIA was significantly lower in the 1988 cohort than the 1961 cohort (0.66 vs. 1.01 per 1000 person-years, p = 0.02). While elevated systolic blood pressure was significantly associated with the risk of TIA in both cohorts, glucose intolerance and higher serum cholesterol levels were associated with TIA risk only in the 1988 cohort. The subjects experiencing TIA had approximately 7–8-fold higher risks for the 10-year incidence of total and ischemic strokes compared with the corresponding control subjects without TIA both in the 1961 and 1988 sub-cohorts, and the relative risks were not significantly different between sub-cohorts. ConclusionsOur results suggest that the incidence of TIA decreased during the past half century, probably due to the spread of antihypertensive treatments in the general Japanese population.