Low-dose aspirin and risk of breast cancer: a Norwegian population-based cohort study of one million women

AbstractSeveral studies evaluated the association between aspirin use and risk of breast cancer (BC), with inconsistent results. We identified women aged  ≥ 50 years residing in Norway between 2004 and 2018, and linked data from nationwide registries; including the Cancer Registry of Norway, the Norwegian Prescription Database, and national health surveys. We used Cox regression models to estimate the association between low-dose aspirin use a nd BC risk, overall and by BC characteristics, women’s age and body mass index (BMI), adjusting for sociodemographic factors and use of other medications. We included 1,083,629 women. During a median follow-up of 11.6 years, 257,442 (24%) women used aspirin, and 29,533 (3%) BCs occurred. For cur rent use of aspirin, compared to never use, we found an indication of a reduced risk of oestrogen receptor-positive (ER +) BC (hazard ratio [HR] = 0.96, 95% confidence interval [CI]: 0.92–1.00), but not ER-negative BC (HR = 1.01, 95%CI: 0.90–1.13). The association with ER + BC was only found in women aged ≥ 65 years (HR = 0.95, 95%CI: 0.90–0.99), and became stronger as the duration of use increased (use of ≥ 4 years HR = 0.91, 95%CI: 0.85–0.98). BMI was available for 450,080 (42%) women. Current use of aspirin was associated with a reduced risk of ER  + BC in women with BMI ≥ 25 (HR = 0.91, 95%CI: 0.83–0.99; HR = 0.86, 95%CI: 0.75–0.97 for use of ≥ 4 years), but n...
Source: European Journal of Epidemiology - Category: Epidemiology Source Type: research