Use of antihypertensive medications and breast cancer risk

Use of specific antihypertensive medications (AHTs) has been hypothesized to increase breast cancer risk, but results across published studies are inconsistent. We re-evaluated the relationship between AHT use and breast cancer risk in a prospective cohort of 3,201 women a parts per thousand yen65 years of age at recruitment now with more than double the length of follow-up (12 vs. 5 years) and substantially more breast cancer diagnoses (188 compared with 75 cases). We estimated the association between AHT use overall as well as use of specific formulations (based on data collected annually) and breast cancer risk using multivariate-adjusted Cox regression. Compared with women who reported no use of AHTs, women who had used calcium channel blockers (CCB) within the past two years had a 1.6-fold increased risk of breast cancer (95 % confidence interval (CI): 1.0-2.5), and in particular, recent users of immediate-release CCBs had a 2.4-fold increased risk (95 % CI: 1.3-4.5). Neither ever nor recent use of any other type of AHT was associated with breast cancer risk. While the observed association between immediate-release CCBs and breast cancer risk is based on a small sample size and needs to be interpreted cautiously, this result is consistent with others in the literature. However, given declines in use of these preparations in favor of sustained-release CCBs, which was not related to risk, the potential clinical and public health impact of this association is limited. This study also adds to the evidence that other commonly used AHTs are not strongly related to breast cancer risk.