Transient ischemic attack: Incidence and early risk of stroke in northern Portugal from 1998–2000 to 2009–2011

Abstract

Objective A decline in TIA incidence would be expected mirroring stroke trends, but patient's awareness of symptoms/signs, improved diagnostic procedures and changes in severity of vascular disease may raise TIA incidence. We aimed to estimate changes in TIA incidence and 30-day stroke risk in Portugal. Methods Data from two prospective community-based registers of first-ever TIA in 104,700 (1998–2000) and 118,232 (2009–2011) persons were collected using comprehensive case ascertainment methods. Incidence and stroke risk from TIA onset were compared using different inception cohorts. ABCD2 was used to stratified stroke risk. Results Overall, 141 patients were included in 1998–2000 and 174 in 2009–2011. Crude annual incidence rate increased from 67 to 74/100,000 (IRR=1.12; 95% CI, 0.90–1.40), particularly in men under 65 years (IRR=1.79; 95% CI, 1.06–3.04). Male/female IRR increased from 1.20 (0.86–1.68) in 1998–2000 to 1.77 (1.31–2.39) in 2009–2011, after adjustment for age. Better control of vascular risk factors (VRFs) accounted for lower ABCD2 scores in 2009–2011. The 30-day stroke risk was similar in study periods (18.4% vs. 16.7%, p > 0.7), decreasing from 16.1% to 8.2% ( p < 0.042) excluding patients reporting TIA after stroke occurrence and from 12.2% to 4.0% ( p < 0.011) further excluding patients who had stroke in ambulance/hospital. ABCD2 discriminated stroke risk only in 1998–2000; stroke severity decreased while posterior circulation stroke was more common in 2009–2011. Conclusion Despite a stable TIA incidence across periods, the risk increased in men compared to women. Better control of VRF accounted for lower ABCD2 scores and secondary prevention reduced stroke risk. Men under 65 years emerge as a preferential target for primary and secondary prevention.