INCIDENCE OF TRANSIENT ISCHEMIC ATTACK IN ROCHESTER, MINNESOTA, 1985-1989

Background and Purpose-There is scant information available on the inc idence of transient ischemic attack (TIA) in a defined population. Thi s study defines incidence rates of first TIA and subtypes of TIA durin g 1985-1989 and compares the incidence to that obtained from a 1960-19 72 cohort study. Methods-Medical records of all residents of Rochester with potential diagnosis of TIA during 1985-1989 were screened to det ermine whether the case met the criteria for TIA. All available data w ere used to determine the vascular distribution of the TIA. Average an nual age- and sex-adjusted incidence rates were calculated for 1985-19 89, and results were compared with incidence rates determined in a Roc hester-based 1960-1972 cohort study, Results-Two hundred two cases of first TIA or amaurosis fugax occurred among Rochester residents during 1985-1989, The age- and sex-adjusted incidence rate for any TIA was 6 8/100 000 population, Incidence of amaurosis fugax was 13/100 000; ant erior circulation (cerebral) TIA, 38/100 000 and vertebrobasilar distr ibution TIA, 14/100 000. rates were similar to those determined from a 1960-1972 cohort study. Conclusions-The incidence rate of TIA is 41% that of stroke incidence. TIA incidence in Rochester, Minn, is higher than has been previously reported for other sites throughout the world . Although comparison with prior time periods is difficult because of ascertainment issues, it appears that there has been no significant ch ange in TIA incidence since the decade of the 1960s or earlier. This s uggests that the most common mechanism for TIA(atherosclerosis) has no t changed in prevalence, nor have risk factors leading to this mechani sm.