Short-term and long-term risk of incident ischemic stroke after transient ischemic attack

Abstract

Background and purpose: The relative risk of ischemic stroke associated with transient ischemic attack (TIA) is not well defined because most studies of stroke after TIA did not include comparison groups. We sought to estimate short-term and long-term relative risks of ischemic stroke associated with clinically diagnosed TIA.

Methods: We used data from a population-based case-control study. Cases were hypertensive men and women and postmenopausal women, ages 30 to 79, with incident ischemic stroke. Control subjects were sampled within strata of age, sex, hypertension status, and calendar year. The index date was the stroke date for cases and a random date for control subjects. Clinically diagnosed TIA was ascertained from medical records. We used logistic regression to calculate ORs.

Results: The study included 1914 stroke cases and 9874 control subjects. Clinically diagnosed TIA was present in 215 (11.2%) cases and 252 (2.5%) control subjects. Analyses focused on the most recent TIA before the index date. For TIA <1 month before the index date, the adjusted OR for stroke was 30.4 (95% CI, 10.4 to 89.4); for TIA 1 to 3 months before the index date, it was 18.9 (8.58 to 41.6); for TIA 4 to 6 months before the index date, it was 3.16 (1.27 to 7.82); and for TIA >5 years before the index date, it was 1.87 (1.22 to 2.85).

Conclusions: The relative risk of ischemic stroke was high for TIA diagnosed within the past 3 months and moderately high for TIA diagnosed >5 years in the past compared with no history of clinically diagnosed TIA.

Figure 1

Time from most recent clinically diagnosed transient ischemic attack (TIA) to index date, for ischemic stroke cases and controls with TIA most recently diagnosed within 24 months prior to index date. Open bars represent ischemic stroke cases; solid bars represent controls.

Figure 2

Odds ratios of ischemic stroke for having a history of clinically diagnosed transient ischemic attack (TIA), by time intervals from most recent TIA to index date. Reference group had no history of clinically diagnosed TIA. Marker size is proportional to the number of ischemic stroke cases. Odds ratios are adjusted for age, sex, hypertension status, calendar year, systolic blood pressure, coronary heart disease, chronic congestive heart failure, atrial fibrillation, peripheral vascular disease, carotid endarterectomy, prosthetic heart valves, medically treated diabetes, current smoking, and current estrogen use.