Washington, May 20 : Contrary to previous study results, coronary bypass surgery is not responsible for long-term cognitive decline in patients, suggests a new study.
Lead researchers Ola A. Selnes and Guy M. McKhann of the Johns Hopkins University School of Medicine conducted their study on 152 patients who had bypass surgery and 92 patients with coronary artery disease who did not have surgical intervention.
The patients then underwent a series of memory and other cognitive tests at the beginning of the study period, and after 3, 12, 36 and 72 months.
Of these, 96 bypass patients and 61 control patients completed cognitive testing after six years.
The findings revealed that there were no significant differences in cognitive scores between the two groups at the beginning of the study.
Both groups showed modest decline in cognitive performance during the study period, but there were no significant differences in the degree of decline between the groups after six years.
The authors suggested that bypass patients had conditions that might be associated with worse cognitive performance, including higher incidence of cardiovascular risk factors, more severe coronary artery disease and more surgery requiring general anesthesia during the follow-up period.
Despite these factors, no differences between the two groups were found.
"The lack of any difference in the long-term cognitive trajectories between the surgery patients and our study controls suggests that late cognitive decline 5 or more years after CABG is not specific to the use of cardiopulmonary bypass," said authors.
As to why cognitive changes occurred in both groups, there is evidence that patients with risk factors for vascular disease (such as high blood pressure) and markers of atherosclerosis (hardening of the arteries) have higher rates of cognitive decline over time than patients without these risk factors.
They said that since both groups in the study had such risk factors, it is likely that the cognitive decline is related either to normal aging in the context of cardiovascular disease or to progression of the underlying vascular disease over time.
The study is published in the May 2008 issue of Annals of Neurology.