RT Journal
A1 Johnson ES, Lanes SF, Wentworth CE, III, Satterfield MH, Abebe BL, Dicker LW
T1 A metaregression analysis of the dose-response effect of aspirin on stroke
JF Archives of Internal Medicine
JO Archives of Internal Medicine
YR 1999
FD June 14
VO 159
IS 11
SP 1248
OP 1253
DO 10.1001/archinte.159.11.1248
UL http://dx.doi.org/10.1001/archinte.159.11.1248
AB Background 
    We evaluated whether the risk of stroke depends on aspirin dose in patients with a previous transient ischemic attack or stroke.Methods 
    We conducted a metaregression analysis of stroke by using published randomized, placebo-controlled trials. We analyzed studies of patients who had recently had a transient ischemic attack or stroke (ie, secondary prevention). We abstracted data on the treatment regimen and stroke. To evaluate the dose-response relationship, we conducted a metaregression analysis of study-specific risk ratios by means of weighted linear regression.Results 
    Eleven randomized, placebo-controlled trials contributed a total of 5228 patients randomized to aspirin only and 4401 patients randomized to placebo only. The slope of the dose-response curve was virtually flat across a wide range of aspirin doses from 50 to 1500 mg/d (P =.49 for test of slope≠0). Summarizing across studies, aspirin decreases the risk of stroke by about 15% (risk ratio, 0.85; 95% confidence interval, 0.77-0.94).Conclusions 
    Aspirin reduces the risk of stroke by approximately 15%, and this effect is uniform across aspirin doses from 50 to 1500 mg/d. The lowest effective aspirin dose has not yet been identified, but it could be lower than 50 mg/d.