Recent observational studies suggest that the risk for stroke may be high in the first 90 days after transient ischemic attack (TIA). This finding may, however, not be consistent across existing studies assessing stroke risk after TIA. The objectives of our study were to conduct a systematic review and meta-analysis of observational studies estimating the risk of stroke at 2, 30, and 90 days after TIA and to explore clinical and methodological factors that may explain variability in findings across studies.
Articles were obtained by searching the Cochrane Database of Systematic Reviews (1996 to present), MEDLINE (1966 to present), EMBASE (1980 to present), CINAHL (1982 to present), and BIOSIS previews (1980 to present). Searches were supplemented by scanning bibliographies of included articles, review articles, and conference proceedings and by contacting an expert in the field. Abstracts were retained if they reported original data and addressed early risk of stroke in patients with TIA. We identified 51 candidate studies reporting early risk of stroke after TIA. Two reviewers independently extracted information from 11 selected studies. Indicators of study quality were collected and included consecutive enrollment, losses to follow-up, explicit criteria used to define TIA and stroke, and method of ascertainment. Pooled early risk of stroke was estimated using fixed and random effects models, and meta-regression was used to assess the association between clinical and methodological factors and the reported early risk of stroke.
Based on a random effects model, the pooled early risk of stroke was 3.5%, 8.0%, and 9.2% at 2, 30, and 90 days after TIA, respectively. Studies reported higher risks when the methodology involved active ascertainment of stroke outcome compared with passive ascertainment. Early risk of stroke was 9.9%, 13.4%, and 17.3% at 2, 30, and 90 days, respectively, when only studies with active outcome ascertainment were considered.
Transient ischemic attack is associated with high early risk of stroke. The methodological design of studies accounts for some of the variability seen in previous reports of early stroke risk after TIA.