Heart bypass surgery increases risk of Alzheimer's

Boston University School of Medicine (BUSM) researchers have discovered that patients who have either coronary artery bypass graft surgery or coronary angioplasty are at an increased risk of developing Alzheimer's disease.

The research, which appears in the current issue of the Journal of Alzheimer's Disease (http://www.j-alz.com), pinpoints stress and trauma of the surgery as the major cause for the increased risk.

Led by Benjamin Wolozin, MD, PhD, professor of pharmacology at BUSM, researchers compared 5,216 people who underwent coronary artery bypass graft surgery (CABG) and 3,954 people who had a percutaneous transluminal coronary angioplasty (PTCA) in 1996 and 1997. Over the course of five years, 78 of the patients who had bypass surgery and 41 of those who had angioplasty developed Alzheimer's disease.

"The coronary bypass patients had a 70 percent increased risk of developing Alzheimer's disease," said Wolozin, co-author of the study. "This increased incidence of neurocognitive degeneration associated with heart bypass surgery provides further incentive for more studies to better characterize the risks of cardiac surgery on the brain."

According to Wolozin, previous studies show some heart surgery patients experience memory problems immediately following the procedure. However, at a one-year follow-up most patients regain cognitive function.

Researchers believe this early cognitive impairment is an immediate reaction to the stress of surgery.

"Heart bypass surgery represents a traumatic insult to the brain, particularly by reducing oxygen supply to the brain and increasing the stress response," said Wolozin.

"We believe that the compensation that occurs by one year masks an underlying deficit in the central nervous system caused by the heart surgery. As individuals age, this underlying deficit might exacerbate progressive cognitive deficits associated with mild cognitive impairment, a precursory phase before diagnosis of Alzheimer's."

Wolozin and his researchers are currently working with researchers from the Framingham Heart Study to determine if these same observations can be duplicated in their studies.

"If these observations are confirmed, there are measures that can be taken to protect the brain during heart bypass surgery," explained Wolozin. "Antioxidants might offer some protection, as well as memantine, a medication that helps slow the progression of Alzheimer's disease. There may also be other neuroprotective agents still in development that could shield the brain from cognitive degeneration during and following surgery."

From Case Western Reserve University

August 25, 2005