Called angiotensin-converting enzyme inhibitors, or ACE inhibitors, the drugs are used to treat high blood pressure. Only ACE inhibitors that can penetrate the blood-brain barrier were shown to have the effect on Alzheimer's. The blood-brain barrier is a natural protective mechanism that shields the brain from foreign substances.
The study involved 162 people in Japan living in long-term care facilities with mild to moderate Alzheimer's disease and high blood pressure. The participants were divided into three groups. For one year, each group received either a brain-penetrating ACE inhibitor, a non-brain-penetrating ACE inhibitor, or another type of blood pressure drug, called a calcium channel blocker. Those in the brain-penetrating ACE inhibitor groups received one of two drugs - perindopril or captopril.
The participants' thinking and memory skills were tested at the beginning of the study and again at the end. The thinking and memory skills of those who took the brain-penetrating ACE inhibitors declined only slightly over the year. The skills of those who took the other drugs declined significantly.
At the beginning of the study, the participants had an average score of about 20 on the exam. The scores of those on brain-penetrating ACE inhibitors declined by an average of .6 points. The scores of those on non-brain-penetrating ACE inhibitors declined by an average of 4.6 points. The average decline was 4.9 points for those on calcium channel blockers.
"These brain-penetrating ACE inhibitors might have benefits not only for the prevention but also for the treatment of mild to moderate Alzheimer's," said study author Takashi Ohrui, MD, of Tohoku University School of Medicine in Sendai, Japan.
"These findings are provocative and exciting, but the results must be replicated in carefully controlled, randomized, blinded studies," said neurologist David Knopman, MD, of the Mayo Clinic in Rochester, Minn., who wrote a commentary on the study.
Knopman noted that the study has several limitations. The participants knew which drug they received, and the researchers were not blinded to which participants received which drug. Blind studies are considered more scientifically accurate, because bias cannot be introduced. Another weakness is that there is no way to tell whether one of the brain-penetrating ACE inhibitors was more effective than the other in slowing the effects of Alzheimer's disease, Knopman said.
The researchers don't know how the brain-penetrating ACE inhibitors work to slow the cognitive decline in Alzheimer's. The brain-penetrating ACE inhibitors did not lower the blood pressure more than the other drugs in the study. Researchers have found more angiotensin-converting enzyme (ACE) in the brains of people with Alzheimer's disease than people who don't have the disease. The brain's renin-angiotensin system controls blood pressure and may play an important role in learning and memory processes.
"The ACE inhibitors may work directly on the renin-angiotensin system in the brain," Ohrui said.
The American Academy of Neurology, an association of more than 18,000 neurologists and neuroscience professionals, is dedicated to improving patient care through education and research. A neurologist is a doctor with specialized training in diagnosing, treating and managing disorders of the brain and nervous system such as multiple sclerosis, restless legs syndrome, Alzheimer's disease, narcolepsy, and stroke.
For more information about the American Academy of Neurology, visit its Website at www.aan.com.