Antihypertensive agents and the risk of breast cancer in women aged 55 years and older: a nested case-control study

Objective:The study aimed to investigate the association of long-term use of different antihypertensive agents with incident breast cancer.Methods:A total of 794533 women aged at least 55 years were identified from Taiwan National Health Insurance claims database during 2001-2011. As of 31 December 2011, incident breast cancer patients were included as cases, and 1:4 age-matched controls were selected by risk-set sampling scheme. Logistic regression models were applied to estimate the odds ratios (ORs) and 95% confidence intervals (CIs) of breast cancer incidence associated with different durations of use of angiotensin-converting enzyme inhibitors/angiotensin receptor blockers, -blockers, and dihydropyridine calcium channel blockers (DHP CCBs). Different restriction rules were applied to reveal the potential effects of confounding by indication.Results:Among the 9397 incident breast cancer patients and 37588 controls, a significantly elevated risk was found for relatively short-term use of DHP CCBs (<6 years) but not in those observed for more than 6 years. There was no association between either angiotensin-converting enzyme inhibitors/angiotensin receptor blockers or -blockers use and breast cancer. Although restricting our analyses to those with any prescription of antihypertensive medications in 2001 or those with diagnosis of hypertension, there was no longer a statistically significant association between any use of DHP CCBs and breast cancer (OR: 1.21, 95% CI: 0.88-1.67 for the former, and OR: 1.71, 95% CI: 0.99-2.95 for the latter).Conclusion:The results demonstrated the potential effect of confounding by indication, and thus, did not suggest any association of the use of antihypertensive medication and breast cancer risk.