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Jan. 12, 2010 -- Drugs commonly used to treat high blood pressure and heart disease may reduce the risk of dementia and Alzheimer's disease, a new study suggests.

Boston University scientists, reporting in the journal BMJ, say a class of high blood pressure drugs called angiotensin receptor blockers is associated with a striking decrease in the risk of occurrence and progression of dementia.

The researchers, using information from a U.S. Department of Health System Veterans Affairs database of more than 5 million people, examined records of more than 800,000 predominantly male patients 65 or older.

The researchers compared the patients in groups that included those using an angiotensin receptor blocker (ARB); those using an ACE inhibitor called lisinopril (Prinivil, Zestril); and those using other blood pressure/heart disease medications (excluding statins).

Angiotensin receptor blockers include candesartan (Atacand), irbesartan (Avapro), losartan (Cozaar), and valsartan (Diovan).

There were no differences in average blood pressure among the three groups.

The patients taking an angiotensin receptor blocker had a 19% lower risk of developing dementia compared to those taking lisinopril and a 24% lower risk compared to use of other blood pressure/heart medications. People taking both an ACE inhibitor and an angiotensin receptor blocker, which both target the angiotensin system, had a 46% lower risk of dementia compared with those taking other medications.

The researchers also studied records of patients who already were suffering from dementia or Alzheimer's. Those patients taking ARBs, the scientists report, had a lower risk of being admitted to a nursing home or dying. Those taking both an ARB and an ACE inhibitor had a 67% lower chance of being admitted to a nursing home.

The results suggest that ARBs might protect against developing Alzheimer's disease and dementia, the researchers write.

"For those who already have dementia, use of ARBs might delay deterioration of brain function and help keep patients out of nursing homes," says Benjamin Wolozin, MD, PhD, professor of pharmacology at Boston University and one of the study researchers. "The study is particularly interesting because we compared the effects of ARBs to other medications used for treating blood pressure or cardiovascular disease."

The researchers write that they do not know exactly why ARBs might be so beneficial, but they believe the drugs may help prevent and reduce nerve cell injury from stroke or blood vessel damage.

The researchers say they've conducted the first large-scale study to investigate whether angiotensin receptor blockers reduce the risk of developing Alzheimer's or dementia.

The findings of the study are "immense," write Colleen J. Maxwell, PhD, and David B. Hogan, MD, of the University of Calgary in an accompanying editorial. "About 36 million people worldwide have a form of dementia such as Alzheimer's disease," they write. "If survival, prevention or treatment do not improve dramatically, this number could double over the next 20 years."

However, they add, though the findings of the study are dramatic, further work is needed to verify the results.