The association between low-dose aspirin use and the incidence of colorectal cancer: a nationwide cohort study

BackgroundConsiderable evidence suggests that aspirin has a chemopreventive effect on colorectal cancer (CRC). However, optimal dose and treatment duration have not been defined, and data on the effects of low-dose aspirin are contradictory. AimTo determine if the incidence of CRC in patients with low-dose aspirin use was lower than in those without aspirin use. MethodFrom Taiwan's National Health Insurance research database, aspirin users (n=1985) were defined as adults (age 20years) with at least 3.5years of regular low-dose aspirin use (50-150mg per day) between 1998 and 2002. Non-users (n=7940) were those who did not use aspirin and were matched 4:1 with the user group by age, gender, date of ambulatory care (index date), and presence of known risk factors for cardiovascular disease (including hypertension, diabetes mellitus and hyperlipidaemia). Follow-up of the two study groups was made until the end of 2010, and incidences and hazard ratios of colorectal cancer were determined. ResultsDuring a median follow-up period of 8.9years, 129 non-users and 14 users developed CRC, corresponding to incidence rates of 180.43 and 79.42 per 100000 person-years respectively. Duration of aspirin use among users ranged from 3.5 to 12.6years (mean 8.7years). The multivariate-adjusted hazard ratio for CRC was 0.5 (95% confidence interval 0.28-0.87) among users as compared with non-users. ConclusionsLong-term use of low-dose aspirin appears to be associated with a lower incidence of CRC in patients with high cardiovascular risk. Further randomised clinical trials are necessary to confirm these findings.