In participants of the Framingham Heart Study from 1948 to 2017, transient ischemic attack (TIA) was associated with a significantly increased risk of subsequent stroke, according to study findings published in JAMA.
Determining the relationship between TIA and subsequent stroke can improve stroke burden and stroke prevention in the general population. Study researchers sought to assess population-based TIA incidence, as well as and long- and short-term stroke risk following TIA. To accomplish this, they conducted a retrospective analysis of prospectively collected data from the long-term Framingham Heart Study. They included 14,059 participants from the study with no history of TIA or stroke at baseline who were followed from 1948 to 2017. Participants with first incident TIA were matched on age and sex to a sample of participants without TIA.
The primary outcomes included TIA incidence, proportion of post-TIA stroke in the short- (7, 30, and 90 days) compared with the long-term (>1-10 years) follow up. Additionally, the study researchers examined the incidence of stroke following TIA compared with stroke in matched TIA-free control participants, as well as time trends of stroke at 90 days following TIA between 1948 and 1985, 1986 and 1999, and 2000 and 2017.
A total of 435 participants in the sample developed TIA over 66 years of follow up. These patients were matched to 2175 control participants without TIA. The study researchers estimated the crude TIA incidence rate to be 1.19/1000 person-years. Approximately 29.8% (n=130) of participants experienced a stroke over a median follow-up period of 8.86 years. A total of 28 (21.5%) strokes occurred within a 7-day period, while 40 (30.8%) occurred within a 30-day period, 51 (39.2%) occurred within a 90-day period, and 63 (48.5%) occurred more than 1 year following the index TIA.
The median time to stroke from the index TIA was 1.64 (interquartile range, 0.07-6.6) years. The age- and sex-adjusted cumulative 10-year hazard of incident stroke for patients with TIA was 0.46 (95% CI, 0.39-0.55) vs 0.09 (95% CI, 0.08-0.11) for matched control participants without TIA (fully adjusted hazard ratio [HR], 4.37; 95% CI, 3.31-5.78; P <.001).
The 90-day post-TIA stroke risk rate between 1986 and 1999 compared with the risk rate between 1948 and 1985 was 11.1% and 16.7%, respectively. Between 2000 and 2017, the 90-day stroke risk after TIA was 5.9%. Compared with the HR for 90-day stroke risk in first epoch (HR, 1 [reference]), the HR was 0.60 (95% CI, 0.33-1.12) in the second epoch and 0.32 (95% CI, 0.14-0.75) in the third epoch (P =.005 for trend).
Limitations of this study were the inclusion of participants of mostly White European descent, the potential misclassification of TIA in the dataset, and incomplete data regarding medical and surgical treatments following TIA.
Based on these findings, the study researchers concluded, “It is likely that this study’s estimation is a relatively accurate representation of contemporary TIA incidence in the general population.” “The risk of stroke, they added, “was significantly greater after TIA compared with matched control participants who did not have TIA, and the risk of stroke after TIA was significantly lower in the most recent epoch from 2000-2017 compared with an earlier period from 1948-1985.”
Lioutas VA, Ivan CS, Himali JJ, et al. Incidence of transient ischemic attack and association with long-term risk of stroke. JAMA. 2021;325(4):373-381. doi:10.1001/jama.2020.25071