A new study has found that, contrary to current thinking, taking beta blockers that treat high blood pressure does not decrease a person's risk of developing colorectal cancer.

Published in CANCER, a peer-reviewed journal of the American Cancer Society, the study also revealed that even long-term use or subtypes of beta blockers showed no reduction of colorectal cancer risk.

In recent years, researchers have thought that beta blockers, which are prescribed to many older adults for high blood pressure and heart conditions, might be linked with a decreased risk of cancer.

This theory stems from animal and laboratory studies that found that the stress hormone norepinephrine can promote the growth and spread of cancer cells.

Beta blockers inhibit norepinephrine's action, so it stands to reason that the medications could have anticancer properties.

Previous studies on beta blockers' effects on colorectal cancer risk have yielded inconsistent results. To provide more thorough information, Michael Hoffmeister, PhD, of the German Cancer Research Center, in Heidelberg, Germany, and his colleagues conducted personal interviews from 2003 to 2007 with 1,762 patients with colorectal cancer and 1,708 cancer-free individuals.

After taking into consideration certain patient characteristics (such as weight and smoking status) and other factors that might influence the results, the researchers found no link between beta blocker use and colorectal cancer risk.

Previous studies had not taken these factors into consideration. Even when the investigators broke down their analyses by duration of use of beta blockers, specific types of beta blockers, active ingredients (metoprolol, bisoprolol, carvedilol, and atenolol), and sites within the colon or rectum where colorectal cancer developed, there was no link.

Overall, the results of this study do not support the hypothesis that using beta blockers can lower one's colorectal cancer risk. The findings also point to the importance of considering patient characteristics and other factors that might influence the results of studies that look at how medications affect patients' cancer risk.

Source: Wiley-Blackwell