Long-term use of antihypertensive drugs and risk of cancer.
PURPOSE: Determine the relative risk of cancer users of commonly prescribed antihypertensive drugs with a focus on documenting risk in long-term users (>7.5 years). METHODS: We conducted a nested case-control study using the Saskatchewan Health databases. Cancer risks in users of beta-blockers, calcium channel blockers (CCBs), and rennin-angiotensin system inhibitors (RASIs), respectively, were compared to risks in users of thiazide diuretics. RESULTS: A total of 11,697 first cases of cancer and the subset of 6918 subjects who died from cancer were each matched to 10 controls. The mean total duration of use of the four classes of antihypertensive drugs (estimated by dispensation of prescriptions) ranged from 3.6 to 5.7 years. A subgroup of cases was exposed long term (mean total duration of use: 9.7-11.4 years, range: 7.5-23.1 years). Modest differences in risk between users of the four classes were detected for colon, head & neck, lung, and hematological cancers but none of these associations demonstrated a clear dose response relationship for both first cancer and fatal cancer. Otherwise, for cancer at all sites combined and for the four most common cancers, we were able to rule out, with reasonable confidence, small to modest differences in the risk of cancer among users of any duration (upper 95% confidence intervals (CIs): 1.45) and modest to large differences in risk among long-term users (upper 95%CI: 3.06). CONCLUSIONS: The long-term use of commonly prescribed classes of antihypertensive drugs does not appear to promote or initiate cancer.