Prevalence of Colorectal Neoplasms and Mortality in New Users of Low-Dose Aspirin With Lower Gastrointestinal Bleeding

BACKGROUND: Aspirin inhibits platelet function and may therefore accelerate early lower gastrointestinal bleeding (LGIB) from colorectal cancer (CRC) precursor polyps. The bleeding may increase endoscopic polyp detection. STUDY QUESTION: To estimate the prevalence of polyps and CRC comparing new users of low-dose aspirin with nonusers who all received a diagnosis of LGIB and to investigate the mortality among these patients. STUDY DESIGN: Using Danish nationwide health registries, we conducted a cohort study (2006-2013) of all new aspirin users who also received a diagnosis of LGIB (n = 40,578). Each new user was matched with 5 nonusers with LGIB by gender and age at the LGIB diagnosis date. MEASURES AND OUTCOMES: We computed the prevalence and prevalence ratios (PRs) of colorectal polyps and CRCs, and the mortality ratios within 6 months after the LGIB, comparing new users with nonusers. RESULTS: We identified 1038 new aspirin users and 5190 nonusers with LGIB. We observed 220 new users and 950 nonusers recorded with endoscopically detected polyps. New aspirin users had a higher prevalence of conventional {PR = 1.28 [95% confidence interval (CI): 1.06-1.55]} and serrated [PR = 1.31 (95% CI: 0.95-1.80)] polyps. New users and nonusers had a similar prevalence of CRC [PR = 1.04 (95% CI: 0.77-1.39)]. However, after stratifying by location of CRC, the prevalence of proximal tumors was lower [PR = 0.71 (95% CI: 0.35-1.43)] in new users than in nonusers. No difference in mortality was observed. CONCLUSIONS: These findings indicate that new use of low-dose aspirin is associated with an increased detection of colorectal polyps compared with nonuse.