Epidemiology of transient ischemic attack in the Normandy Stroke population-based study.

Introduction: Transient ischemic attack (TIA) is a frequent neurological emergency which management and definition have changed radically over the last 15 years. However, recent epidemiological studies of TIA are scarce. We report here on the impact of the shift from a time-based to a tissue-based definition of TIA on its incidence and risk of recurrence in a new population-based cohort with a high rate of patients investigated by MRI.

Materials and methods: We prospectively included all TIAs that occurred between May 2017 and May 2021 from the Normandy Stroke Study, a population-based registry using multiple overlapping sources for exhaustive case identification in Caen la Mer area. TIAs were classified as either time-based (symptoms <24 h) or tissue-based (<24 h and no lesion on brain imaging). Attack and incidence rates were calculated, as was the 90-day ischemic stroke rate.

Results: Five hundred and sixty-seven TIAs (549 single patients) were included, with 80.6% having a brain MRI. Four hundred and ten (72.3%) met the definition of tissue-based TIA. The age standardized attack (to the 2013 European population) rate was 39.5 (95% CI 35.7-43.5) and the age-standardized incidence rate (first ever cerebrovascular event) was 29.7 (95% CI 27.3-34.2). The overall recurrent stroke rate at 90 days was 2.7%, with no difference between patients with or without ischemic lesions on MRI.

Conclusion: We found that the use of the tissue-based definition of TIA resulted in a 27.5% reduction in incidence as compared to the time-based definition, but had no impact on the 90-day stroke rate. The burden of TIA remains high, and is likely to increase as the population ages.