Background and purpose: There are no community-based studies on the incidence of transient ischemic attacks (TIAs) in Portugal. This study was designed to determine TIA incidence and the risk of stroke occurrence in rural and urban populations in northern Portugal.
Methods: All suspected first-ever TIAs occurring between October 1998 and September 2000 in 18,677 residents in a rural municipality and 86,023 living in the city of Porto were entered into a population-based registry. Standard definitions and comprehensive sources of information were used for identification of patients who were followed up at 3 and 12 months after the TIA.
Results: During a 24-month period, 141 patients with a first-ever TIA were registered, 36 in rural and 104 in urban areas. The vascular territory was carotid in 66.7% of the patients, vertebrobasilar in 29.1%, and undetermined in 4.3%. The overall crude annual incidence rate per 1000 was 0.67 (95% CI, 0.45 to 1.04), 0.61 (95% CI, 0.38 to 1.01) for rural, and 0.96 (95% CI, 0.43 to 2.33) for urban populations. The risk of stroke within the first 7 days of the index event was 12.8% (95% CI, 7.3 to 18.3), reaching 21.4% (95% CI, 14.6 to 28.1) at 1 year. Three factors were associated with stroke occurrence within 120 days after TIA: patients' age > or =65 years and an episode in the carotid distribution lasting > or =3 hours.
Conclusions: The incidence of TIA in northern Portugal, particularly in rural populations, ranks among the highest reported in community-based studies, following closely the stroke incidence trend (ACINrpc). Early recognition of TIA by patients and physicians is crucial for effective stroke prevention.