The finding could have important implications not only for bypass patients, but also for all those who are vulnerable to heart disease.
Other studies have found a serious decline in mental function in at least 40 percent of people undergoing CAGB (coronary artery bypass grafting), as it is formally called. However, neurologists at the University of Würzburg report in today's issue of Neurology that in their five-year study of 52 bypass patients, "no individual patient showed a global decline at follow-up compared to baseline" and that "compared to discharge [after surgery], the cohort generally showed better scores."
The best explanation for those results, says Dr. Wolfgang Müllges, a consultant neurologist at Würzburg and lead author of the paper, is that a strict effort was made to control such heart disease risk factors as high blood pressure, high blood cholesterol and diabetes.
"We have only a hypothesis," Müllges concedes. "But what we did for risk control produced numbers that were not reported in other studies. These efforts seem to make the long-term prognosis better, especially for elderly patients."
That hypothesis seems to be valid to warrant further study, says Ola A. Selnes, an associate professor of neurology at Johns Hopkins University School of Medicine who co-authored an accompanying editorial. Last year, he reported a similar study that did find a long-term decline in mental function for bypass patients.
"The hypothesis is that by controlling as strictly as possible the risk factors for cardiovascular disease after surgery -- all the patients stopped smoking, all started medications for high blood pressure and high cholesterol -- they had a favorable outlook," Selnes says. "This is an interesting idea that we have to investigate in future studies."
Doctors and patients usually do pay attention to risk factor control, Selnes says, "but the real issue is how compliant you are. You could envision the port-operative reaction of a patient who had surgery, who may well think you can go on doing what you have been doing without worrying."
Selnes says the studies he has done show that bypass patients are back to pre-surgery levels of mental function within a year after the procedure, but then begin to go downhill. There could be "a very slow process" in which the brain is affected if cardiovascular risk factors are not controlled, Selnes says.
Some recent studies of high blood cholesterol levels have indicated that they could have an adverse effect on mental function, he notes.
"If this turns out to be true, the public health implications could be enormous," Selnes says. "There are 400,000 to 500,000 patients a year undergoing bypass surgery."
Müllges says the study "is very good news" because it helps lift a cloud hanging over bypass surgery.
"Other studies have found that nearly half of all patients had a cognitive decline that was attributed to CAGB itself," he says. "If you think you have a 42 percent chance of becoming demented, you might not have CAGB."
The new report is just a suggestion, and "the real answer will come only when we have controlled studies," Selnes says. "That could be a very slow process."
However, no harm is done by following strict rules about blood pressure, cholesterol and other factors that affect the risk for heart disease -- and possibly mental function, he says.
What To Do