Each year, more than 400,000 patients undergo open heart surgery requiring cardiopulmonary bypass, and as many as 75 percent suffer neurological complications, ranging from transient cognitive changes to stroke. While the elderly are known to be at higher risk, in more than half the cases the underlying predisposition for impairment is not known.
In the study patients were given a battery of cognitive tests prior to surgery and 6 weeks after surgery.
The study also showed that a higher level of education is protective of cognitive decline.
"We don't know the exact reason for this, but it is probably that more well-educated people have a greater functional reserve of brain cells, have more experience in test-taking, and may have developed more alternative neurological pathways," Newman said.
While these findings do not explain every case of cognitive decline following heart surgery, Newman said that they will be important in developing protective strategies for susceptible heart patients. At this point, the situation is similar to that of Alzheimer's disease -- physicians can determine who is the most susceptible, but, there are no current treatments.
Newman believes that these findings give more information to patients and their physicians as they weigh the risks and benefits of heart surgery.
He stressed that further studies with more patients are needed to prove a definite link between cognitive decline and the APOE variant. Newman and colleagues plan to follow heart patients for five years to determine how their cognitive status changes.