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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.