Long-Term Incidence of Ischemic Stroke Following Transient Ischemic Attack

The short-term risk of ischemic stroke following a transient ischemic attack (TIA) is as high as 20% and has been studied extensively. Yet, the long-term risk of stroke remains scarcely described, especially in a contemporary setting and in unselected cohorts. Acute stroke care and treatments, particularly with thrombolysis, have developed significantly, yet the long-term preventive strategies lack evidence. Knowing the long-term risk of stroke is a prerequisite for future randomized clinical trials on various secondary treatment prophylaxis, especially antithrombotic medication.

In a nationwide cohort from the Danish Stroke Registry, we aimed to investigate the 5-year comparative risks of ischemic stroke and all-cause mortality in patients with TIA. Patients with first-time TIA (n = 21,500) were included and matched with the background population (n = 86,000) and a control stroke population (n = 21,500). The median age was 71 years and 53% were male in the three matched study groups. The crude cumulative incidence of ischemic stroke was 6.1% (95% CI, 5.7–6.5), significantly higher than that in the background population ([1.5%; 95% CI, 1.4–1.6; P < .01]; [aHR, 5.14; 95% CI, 4.65–5.69]), yet lower than that in the control stroke population ([8.9%; 95% CI, 8.4–9.4; P < .01]; [aHR, 0.58; 95% CI, 0.53–0.64]). Importantly, these differences persisted beyond the first 90 days. The same result was observed for the outcome of mortality; however, patients with TIA had a 60% lower rate of mortality than the control stroke population. This highlights that, by preventing a stroke among patients with TIA, we may also prevent excess mortality.¹

This study along with two other studies, the Framingham Heart Study² and the TIAregistry.org,³ provide consistent results on three different populations; stroke risk continues to rise beyond the first high-risk period. A window of opportunity exists to reduce stroke risk among patients with TIA. Special attention to cardiovascular risk factors is needed in the long term after TIA, and further research on preventive measures is paramount.

References

1. Vinding NE, Butt JH, Lauridsen MD, et al. Long-Term Incidence of Ischemic Stroke Following Transient Ischemic Attack: A Nationwide Study During 2014–2020. Circulation. 2023 Aug 25. doi: 10.1161/CIRCULATIONAHA.123.065446. Online ahead of print. https://www.ahajournals.org/doi/10.1161/CIRCULATIONAHA.123.065446
2. 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. https://jamanetwork.com/journals/jama/fullarticle/2775447
3. Amarenco P, Lavallée PC, Monteiro Tavares L, et al. Five-Year Risk of Stroke After TIA or Minor Ischemic Stroke. N Engl J Med. 2018;378(23):2182-2190. https://www.nejm.org/doi/10.1056/NEJMoa1802712