Data (comma-separated values format) and analytical code (Stata format) relating to: Moriarty F, Ebell MH. A Comparison of Contemporary versus Older Studies of Aspirin for Primary Prevention. 2019 (under review). Available on medRxiv at https://doi.org/10.1101/19004267 Abstract Purpose: This study compares the benefits and harms of aspirin for primary prevention before and after widespread use of statins and colorectal cancer screening. Methods: We compared studies of aspirin for primary prevention that recruited patients from 2005 onward with previous individual patient meta-analyses that recruited patients from 1978 to 2002. Data for contemporary studies were synthesized using random-effects models. We report vascular (major adverse cardiovascular events [MACE], myocardial infarction [MI], stroke), bleeding, cancer, and mortality outcomes. Results: The IPD analyses of older studies included 95,456 patients for CV prevention and 25,270 for cancer mortality, while the four newer studies had 61,604 patients. Relative risks for vascular outcomes for older vs newer studies follow: MACE: 0.89 (95% CI 0.83-0.95) vs 0.93 (0.86-0.99); fatal hemorrhagic stroke: 1.73 (1.11-2.72) vs 1.06 (0.66-1.70); any ischemic stroke: 0.86 (0.74-1.00) vs 0.86 (0.75-0.98); any MI: 0.84 (0.77-0.92) vs 0.88 (0.77-1.00); and non-fatal MI: 0.79 (0.71-0.88) vs 0.94 (0.83-1.08). Cancer death was not significantly decreased in newer studies (RR 1.11, 0.92-1.34). Major hemorrhage was significantly increased for both older and newer studies (RR 1.48, 95% CI 1.25-1.76 vs 1.37, 95% CI 1.24-1.53). There was no effect in either group on all-cause mortality, cardiovascular mortality, fatal stroke, or fatal MI. Conclusions: In the modern era characterized by widespread statin use and cancer screening, aspirin does not reduce the risk of non-fatal MI or cancer death. There are no mortality benefits and a significant risk of major hemorrhage. Aspirin should no longer be recommended for primary prevention. Version 1.1 - Updated Stata code to correct name of .csv data file for import.