Transient ischemic attacks in the community: occurrence and clinical characteristics. A population survey in the area of Florence, Italy.

A simple self-administered questionnaire was mailed to a population sample of 8,626 (40-65 years old) to identify transient ischemic attacks (TIAs) that occurred in the previous 12 months. This study was conducted in a well-defined, medically controlled geographic area. 75.4% of the questionnaires were returned. The procedure identified 52 TIA cases (43 definite and 9 uncertain). The 12-month period prevalence for TIAs was 6.6 per 1,000 (95% confidence limits of 4.8-8.9) among the respondents. The annual incidence rate for first TIAs was 3.1 per 1,000 (95% confidence limits of 1.9-4.7). Our results differ from those reported in hospital series or in population surveys based on clinical records, with higher incidence and prevalence rates, female preponderance and higher frequency of vertebrobasilar attacks.