Effect of Prior Aspirin Use on Stroke Severity in the Trial of Org 10172 in Acute Stroke Treatment (TOAST)

Background and Purpose — Although the efficacy of aspirin in reducing stroke incidence is clear, its role in reducing stroke severity is disputed. This study compares stroke severity between patients who did or did not take aspirin in the week before stroke and enrollment in the Trial of Org 10172 in Acute Stroke Treatment (TOAST). Methods — Of 1275 patients randomized, 509 reported aspirin use in the week before stroke; 766 did not. Clinical stroke severity was assessed with the National Institutes of Health Stroke Scale (NIHSS) and the Supplementary Motor Examination (SME) at trial entry and at 3 months. Using these scales, we compared the categorization of stroke severity (mild, moderate, and severe) and mean scores between aspirin users and nonusers. Results — The difference in distribution of baseline NIHSS scores was statistically significant between aspirin users and nonusers ( P =0.006), with a greater percentage of milder strokes among aspirin users. The difference in mean baseline NIHSS scores was also significantly lower in aspirin users (8.2) and nonusers (9.3) ( P =0.003). The distribution of baseline SME scores and mean SME scores also showed lower stroke severity in aspirin users than in nonusers ( P =0.048 and P =0.004, respectively). At 3 months, differences in stroke severity measured by the SME but not the NIHSS remained statistically significant. Seven-day and 3-month mortality did not differ significantly. Conclusions — In this study aspirin use is associated with milder clinical deficits at stroke onset. These deficits may affect prognosis and influence response to treatment. Future clinical trials should ensure that prestroke aspirin use is comparable in study groups.