Drugs and Alzheimer’s Disease
Posted by medconsumers on January 25, 2010
You’re taking a cholesterol-lowering statin drug like Lipitor or Mevacor to cut your chances of having a heart attack or stroke. Then you’re happy to learn that statin drugs may also reduce the risk of Alzheimer’s disease. Twofers have their appeal, though sometimes a drug taken for two entirely different purposes doesn’t always live up to expectations. Remember how the studies that seemed to back postmenopausal hormones for heart disease prevention also hinted at Alzheimer’s prevention? …that is, until a more rigorous clinical trial showed that hormone therapy actually increased the chance of getting this much-dreaded brain disease.
Two new reviews from the Cochrane Collaboration have dashed hopes for statins as protective against Alzheimer’s disease and one other age-related condition. A newly published large study, however, shows a lower incidence of developing Alzheimer’s disease in elderly people taking one popular class of anti-hypertension drugs.
Anti-Hypertension Drug Class Reduces Risk of Alzheimer’s Disease
People with high blood pressure are usually put on a diuretic, the first-choice drug for this condition. Many of them require another prescription drug, which often comes from a class of anti-hypertensives known as angiotensin receptor blockers, or ARBs. Because cardiovascular problems like high blood pressure and diabetes contribute to the development of dementia, there are good reasons to think that anti-hypertensive drugs may also reduce the incidence of dementia. To test this hypothesis, a research team led by Nien-Chen Li, Boston University School of Public Health, zeroed in on ARBs because drugs in this class are “the most effective agents for lowering blood pressure.” Moreover, they have been shown to lower the rates of congestive heart failure, heart attack, kidney disease, and death more than other anti-hypertensive drugs that act in other ways. (For a list of drugs in the class called ARBS, click here.)
Dr. Li and colleagues analyzed information from the medical records of nearly 820,000 mostly male veterans in the database of the U.S. Veteran Affairs (from 2002 to 2006). The researchers were looking only at records of patients over age 65 years who had been diagnosed with heart disease. The researchers compared the veterans who were taking any one of the standard heart drugs with the veterans taking an ARB. Here is the conclusion: the vets taking an ARB had a “significant reduction in the incidence and progression of Alzheimer’s disease and dementia compared with angiotensin converting enzyme inhibitors. (For a list of drugs in this class, click here.) Most of the veterans were taking lisinopril (brand names: Prinivil, Zestril).
Statins Can’t Prevent Alzheimer’s Disease or Macular Degeneration
The hope that lowering blood levels of cholesterol would provide a buffer against Alzheimer’s disease was certainly plausible. Animal studies and population studies indicate that high blood levels of cholesterol could promote pathological changes in the brain that lead to Alzheimer’s disease. And some researchers hypothesized that a reduction in cholesterol might turn the process around.
A new Cochrane review relied on two major drugs trials that had randomly assigned the participants to a statin or a placebo in order to see whether the drug reduced the risk of death and heart attack in elderly people. Most of the participants had heart disease and high cholesterol and some only had high cholesterol. The trials had a combined total of nearly 12,000 participants who were at least 70 years of age when they entered the study.
At the three- to five-year follow-up, the incidence of dementia was exactly the same in both the placebo and the statin groups. The same finding showed up in a final, follow-up telephone survey: There was no difference in cognition between groups, nor was there any evidence that statins were detrimental to cognition.
Another new Cochrane review was based on an observation regarding the development of age-related macular degeneration. This eye disease, which causes the loss of central vision, shares some of the risk factors for atherosclerosis. The Cochrane reviewers searched the published literature to find studies that explored the question of whether statins have a protective effect against macular degeneration. The short answer is no, according to the only study published so far.
For more information
Many commonly prescribed drugs are known to cause cognitive dysfunction. Read our 2008 article entitled, “Drug-Induced Memory Loss.”
Maryann Napoli, Center for Medical Consumers(c)