Three multicentre RCTs (n=2,338) were included. Each study was considered of high quality (Jadad score 5). Follow-up was one year in two studies and three years in the other study. Most patients (93%) completed the follow-up colonoscopy.
High-dose aspirin (300mg/day or 325mg/day) and low-dose aspirin (81mg/day or 160mg/day) reduced recurrence of adenomas (high dose RR 0.86, 95% CI 0.76 to 0.98; three studies and low dose RR 0.83, 95% CI 0.71 to 0.97; two studies). Any dose of aspirin reduced recurrence of adenomas (RR 0.84, 95% 0.75 to 0.94; three studies). Recurrence of advanced adenomas was reduced with any dose of aspirin (RR 0.66, 95% 0.51 to 0.84; three studies).
There was no evidence of heterogeneity in any analyses. Results of tests for publication bias and sensitivity analyses were not reported.