Post-TIA Stroke Risk Has Come Down Over Time, but Vigilance Still Needed

Although the risk of stroke after a transient ischemic attack has come down over the past several decades, it remains elevated, underscoring the importance of seeking immediate medical attention after the episode, findings from the Framingham Heart Study affirm.

Over the entire study period, which spanned the years 1948 to 2017, TIA incidence remained relatively unchanged. But the proportion of patients who went on to have a stroke within 90 days of a TIA declined from 16.7% in 1948-1985 to 11.1% in 1986-1999, and then further to 5.9% in 2000-2017, researchers led by Vasileios-Arsenios Lioutas, MD (Beth Israel Deaconess Medical Center, Boston, MA), report.

The heightened risk of stroke after a TIA was expected, Lioutas said, yet the timing of the strokes was a bit surprising. Stroke risk was previously thought to be front-loaded in the first few months after a TIA, and indeed many of the events observed in this study (39.2%) occurred within 90 days. But nearly half (48.5%) occurred more than a year after the TIA.

“Do not relax too much if you go beyond 90 days or 1 year,” Lioutas said. “The risk can be high even beyond 1 year, so continue with adherence to whatever medications are prescribed. Physicians should make sure that these patients are followed up and their blood pressure is well controlled and they take whatever is prescribed to them—aspirin, anticoagulants, whatever they need—because the risk remains high even years after a TIA.”

Secondary Prevention Improves

For the study, published in the January 26, 2021, issue of JAMA, the investigators pulled data from the original, offspring, and third-generation cohorts of the Framingham Heart Study, which has been ongoing since 1948. The analysis included 14,059 participants who had no history of stroke or TIA at baseline. To look for differences in stroke risk, the 435 patients who subsequently had a TIA (mean age 72 years; 53% women) were matched by age and sex to 2,175 participants who did not have a TIA.

Over a median follow-up of 8.86 years after TIA, 29.8% of patients had a stroke. Lioutas called that “a pretty chilling statistic.” The median time to stroke after a TIA was 1.64 years.

Consistent with prior studies, the researchers confirmed that TIA was associated with an increased risk of stroke over the next 10 years (fully adjusted HR 4.37; 95% CI 3.31-5.78).

Do not relax too much if you go beyond 90 days or 1 year. Vasileios-Arsenios Lioutas

That stroke risk declined over the decades, however, with TIA patients in the most-recent time period having a significantly lower risk of stroke at 90 days compared with those in the earliest time period (HR 0.32; 95% CI 0.14-0.75). Similar trends were seen when evaluating 1-, 5-, and 10-year stroke risks.

“The good news is when we looked at the trends over time, we found that we’ve gotten a lot better at preventing strokes from TIA in the last 20 years or so,” Lioutas said. The favorable change “probably has to do with a combination of much-better preventive care, more-thorough workup, better medications, and then also of course improved public awareness” about the seriousness of TIA.

Lee Schwamm, MD (Massachusetts General Hospital, Boston), who was not involved in the study, agreed that a combination of factors likely played into the declining post-TIA stroke risks. He noted that physicians have gotten better at differentiating between TIA and stroke over time, which would lower the stroke risk of more-contemporary TIA cohorts. Improvements in medical therapy also likely played a role, with improvements in control of hypertension and dyslipidemia, for instance, and the introduction of better antithrombotic drugs like clopidogrel.

“Overall, the risk profile is better for these patients, and our preventive treatments are also better,” said Schwamm, who is chair of the American Stroke Association advisory council.

TIA Is a Medical Emergency

Despite the positive signals, these data underscore that TIAs require immediate medical attention, Schwamm said, pointing to the high number of strokes that occur shortly after an episode. “TIAs are not something that you should sleep on over the weekend and then see your primary care doctor about next week,” he stressed. “TIAs are a medical emergency and you should go to the hospital to be evaluated or to a rapid TIA clinic to make sure you don’t have a risk of impending stroke.”

When you ask the patients with stroke, they frequently endorse the fact that they had a little something that happened a day or week beforehand and that was a preview of the stroke and was an opportunity for prevention that was missed. Lee Schwamm

Awareness of the severity of TIAs may have improved over time, yet it’s still not where it should be, Schwamm indicated. “From my own personal experience, many patients who experience symptoms of a TIA don’t seek medical attention. They wait until they’ve had another spell or, unfortunately, until they’ve had a stroke,” he said. “When you ask the patients with stroke, they frequently endorse the fact that they had a little something that happened a day or week beforehand and that was a preview of the stroke and was an opportunity for prevention that was missed.”

Lioutas echoed that idea, calling a TIA “a very loud bell that people should take very seriously. If taken seriously and addressed appropriately, it can prevent a future catastrophic stroke from happening.”

Patients who have a TIA should not be discouraged from going to the hospital during the COVID-19 pandemic, he added. “Don’t postpone it, because the repercussions could be disastrous,” he said. “Treat it the same way as you would treat it outside of COVID, and I can assure you that hospitals and physicians and systems of care are ready to tackle that.”