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Incidence of TIA and Association With Long-Term Stroke Risk
Quick Takes
- Of subjects enrolled in the Framingham Heart Study who were free of TIA or stroke at baseline, first-ever TIA occurred in approximately 3%.
- The risk of stroke was almost five times higher in subjects who had previously had a TIA compared to subjects who had not.
- The short- and long-term risk of stroke after TIA in this Framingham Heart Study cohort has decreased over decades, presumably due to improved secondary stroke prevention.
Study Questions:
What is the incidence of first-ever transient ischemic attack (TIA) in the general population? Given improvement in secondary stroke prevention, has the short- and long-term risk of stroke after TIA decreased over time?
Methods:
This is a retrospective analysis of the longitudinal Framingham Heart Study. Included subjects had no history of TIA or stroke at baseline. Active surveillance was used to identify symptoms concerning for TIA or stroke. If a subject developed such symptoms, he or she was evaluated by a neurologist with stroke expertise to determine whether TIA or stroke was the correct diagnosis. Each participant with TIA was randomly assigned five age- and sex-matched stroke-free controls. Outcomes of interest included the incidence of new TIA; proportion of stroke occurring after TIA at 7 days, 30 days, 90 days, and >1 year; and time trends in stroke risk at 90 days for three different extended time periods (>10-year epochs). Both ischemic and hemorrhagic strokes were included.
Results:
The entire cohort consisted of 14,059 participants with 366,209 person-years of follow-up; 435 patients (3.1%) had a first-ever TIA. In the most recent epoch (2000-2014), the crude incidence rate of first-ever TIA was 1.29 per 1,000 person-years. There were 130 strokes among the 435 participants with TIA compared with 165 strokes among the 2,175 matched control subjects without TIA (adjusted hazard ratio, 4.81; 95% confidence interval, 3.82-6.06). Among the 130 subjects with stroke after the index TIA, 28 strokes (21.5%) occurred within 7 days; 40 (31%) occurred within 30 days; 51 (39%) occurred within 90 days; and 63 (48.5%) occurred >1 year after TIA. Compared to the first epoch studied (1948-1985), there was a decrease in post-TIA stroke incidence at 90 days, 1 year, 5 years, and 10 years across the 1986-1999 epoch and the 2000-2017 epoch.
Conclusions:
In this large population-based cohort study, the incidence of first-ever TIA was 3.1%. The risk of stroke was almost five times higher in subjects who had had a TIA compared to subjects who had not. The short- and long-term risk of stroke after TIA in this large cohort has decreased over time.
Perspective:
Studies involving TIA can be tricky because many neurologic symptoms are misclassified as TIA. In addition, TIA can be misclassified as stroke because of a positive magnetic resonance imaging. This study well addresses these limitations by using a standardized clinical definition for TIA and careful case adjudication. The large cohort size and long duration of follow-up in this study allowed for an estimation of the population’s long-term risk of stroke after first-ever TIA. The reduction in short- and long-term risk of stroke after TIA despite an aging population is likely due to improved secondary stroke prevention.
Clinical Topics: Cardiovascular Care Team, Geriatric Cardiology, Noninvasive Imaging, Prevention, Magnetic Resonance Imaging
Keywords: Brain Ischemia, Geriatrics, Hemorrhage, Intracranial Hemorrhages, Ischemic Attack, Transient, Magnetic Resonance Imaging, Neurology, Risk Factors, Secondary Prevention, Stroke, Vascular Diseases
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