The short-term incidence of ischemic stroke after a transient ischemic attack (TIA) is high. However, data on the long-term incidence are not well known but are needed to guide preventive strategies.
Patients with first-time TIA (index date) in the Danish Stroke Registry (January 2014-December 2020) were included and matched 1:4 with individuals from the background population and 1:1 with patients with a first-time ischemic stroke based on age, sex, and calendar year. The incidences of ischemic stroke and mortality from index date were estimated by Aalen-Johansen and Kaplan-Meier estimators, respectively, and compared between groups using multivariable Cox regression.
We included 21,500 patients with TIA, 86,000 patients from the background population, and 21,500 patients with ischemic stroke (median age 70.8 years [25th-75th percentile 60.8-78.7]: 53% men). Patients with TIA had more comorbidities than the background population, yet less than the control stroke population. The five-year incidence of ischemic stroke following TIA (6.1% [95% CI 5.7-6.5]) was higher than the background population (1.5% [95%CI 1.4-1.6], hazard ratio (HR) 5.14 [95%CI 4.65-5.69 ]), but lower than the control stroke population (8.9% [95%CI 8.4-9.4], HR 0.58 [95%CI 0.53-0.64]). The five-year mortality for patients with TIA (18.6 % [95%CI 17.9-19.3]) was higher than the background population (14.8% [95%CI 14.5-15.1 ], HR 1.26 [95%CI 1.20-1.32 ]), but lower than the control stroke population (30.1% [95% CI 29.3-30.9), HR 0.41 [95%CI 0.39-0.44]).
Patients with first-time TIA had an ischemic stroke incidence of 6.1% during the 5-year follow-up period. Following adjustment for relevant comorbidities, this incidence was approximately five-fold higher than what was found for controls in the background population, and 40% lower than for patients with recurrent ischemic stroke.