April 6, 2010
Certain medications commonly used to treat high blood pressure may help protect against Alzheimer’s disease, a new study found. The drugs may also help to slow progression of symptoms in those who already have Alzheimer’s disease.
Using data from more than 800,000 older patients from Veterans Affairs hospitals across the country, investigators from Boston University School of Medicine found that a class of blood pressure drugs called angiotensin receptor blockers, or ARBs, diminished the likelihood that the patients, most of whom were men over 65, would develop Alzheimer’s or other forms of dementia. ARB drugs include candesartan (Atacand), irbesartan (Avapro), losartan (Cozaar), and valsartan (Diovan).
Those who were taking ARBs plus another type of blood pressure drug called lisinopril (brand names Prinivil, Zestril) had an even lower likelihood of developing Alzheimer’s. Lisinopril belongs to a class of drugs known as angiotensin converting enzyme, or ACE, inhibitors. Both ARBs and ACE inhibitors relax blood vessels by acting on a hormone called angiotensin that constricts arteries.
The researchers found that patients taking ARBs had up to a 50 percent lower chance of getting Alzheimer’s disease or dementia. Patients taking both ARBs and ACE inhibitors had a 55 percent lower risk of dementia. The findings appeared in the British medical journal BMJ.
The Boston University researchers also examined patients who were already suffering from Alzheimer’s disease or other forms of dementia. They found those individuals had up to a 67 percent lower chance of being admitted to nursing homes or dying if they were taking both ARBs and ACE inhibitors. Patients who appeared to benefit particularly well from use of ARBs were those who had experienced strokes before or during the course of their illness.
“For those who already have dementia, use of ARBs might delay deterioration of brain function and help keep patients out of nursing homes,” said senior author Dr. Benjamin Wolozin, a professor of pharmacology at Boston University. “The study is particularly interesting because we compared the effects of ARBs to other medications used for treating blood pressure or cardiovascular disease. This suggests that ARBs are more effective than other blood pressure and cardiovascular medications for preventing Alzheimer’s disease or dementia.”
There are several main classes of drugs used to treat hypertension. In addition to ACE inhibitors and ARBs, they include diuretics, or “water pills,” which reduce blood pressure by reducing the amount of fluid the heart must pump, and beta-blockers, which affect the heart’s pumping ability. Which drug or drug combination is right for a patient is determined by factors like how old someone is, their sex, their blood pressure readings, whether they smoke, cholesterol levels, and other illnesses like diabetes or heart failure.
Normal blood pressure is usually considered to be around 120/80, with 80 being the diastolic reading. High blood pressure is often defined as a reading of 140/90 or higher, or taking a medication for the condition.
The researchers are unsure why ARBs might be especially beneficial for those with Alzheimer’s or at risk for it, but they speculate that the drugs may protect against blood vessel damage in the brain. Damage to blood vessels is thought to reduce brain capacity and promote dementia, so reducing this damage might prevent the occurrence or progression of dementia. They also caution that more research is needed to confirm these findings.
The relation between Alzheimer’s and blood pressure remains uncertain. Some studies have found a link between high blood pressure and memory problems; others a link between low blood pressure and memory loss; while still others have found no link at all. The National Institutes of Health is now organizing a large clinical trial to evaluate whether aggressive blood pressure lowering can decrease a number of important health outcomes, including memory loss and Alzheimer’s.
Experts advise everyone to take steps to keep blood pressure in check to avoid strokes and heart disease. And taking measures to protect the heart may have long-term benefits for the brain.
Nien-Chen Li, Austin Lee, Rachel A Whitmer, Miia Kivipelto, Elizabeth Lawler, Lewis E Kazis, and Benjamin Wolozi: “Use of angiotensin receptor blockers and risk of dementia in a predominantly male population: prospective cohort analysis.” BMJ 2010;340:b5465, January 12, 2010.