Trends over time in the risk of stroke after an incident transient ischemic attack

Background and Purpose— Long-term population trends in the early risk of stroke after transient ischemic attack (TIA) are unknown. We hypothesized that there has been an appreciable decline in the risk of stroke after TIA for the last decade. Methods— Population-level cohort study from Victoria, Australia (population 5.6 million), using linked data from hospitals, emergency departments, and death records (2001–2011), with a 2-year clearance period to define incident TIAs. Age-specific rates/1000, yearly incident rate ratios, and age–sex-adjusted risk of stroke after TIA were computed. Results— The mean age of 46 971 patients with TIA was 71 (SD=15), 52% women. In patients ≥65 years, annual TIA rates declined between 2001 and 2011 from 5.8 to 4.8/1000 (men) and from 5.3 to 4.2/1000 (women). Yearly incident rate ratios were 0.97 (95% confidence interval, 0.96–0.98) in men and 0.97 (95% confidence interval, 0.97–0.98) in women. Overall, the 90-day stroke risk was 3.1%. Age–sex-adjusted risk of stroke at 90 days after a TIA decreased by 3% per year (odds ratio for the effect of year, 0.97; 95% confidence interval, 0.95–0.99). Male sex, direct discharge from emergency departments, public hospital care, stroke unit care, and absence of vascular risk factors were associated with a downward yearly trend of stroke within 90 days of TIA. Conclusions— Over the last 10 years, there has been a measurable decline in the 90-day risk of stroke after an incident TIA and overall decline in rates of TIA in Victoria, Australia. These trends may reflect improved primary and secondary prevention efforts for the last decade.