Lower Immunity May Predispose Elderly to Cognitive Decline After CABG

The risk of cognitive decline following coronary artery bypass graft (CABG) surgery with cardiopulmonary bypass appears to be elevated among elderly individuals with low preoperative levels of anti-endotoxin core antibody (EndoCAb).

Dr. Joseph P. Mathew and colleagues at Duke University Medical Center in Durham, North Carolina, measured IgM EndoCAb levels in 343 patients the day before they underwent elective CABG. The procedures were conducted between 1997 and 2000, with patients ranging between 23 and 87 years of age. The findings appear in the February issue of Stroke.

Although the overall cognitive index score improved between the baseline evaluation and that at 6 weeks follow-up, cognitive decline was apparent in about one third of patients (n = 122).

There was a significant relationship between log EndoCAb level and change in cognitive index (p = 0.005). The association was exacerbated by age. Thus, among patients >64 years old whose EndoCAb levels were below the median, the odds ratio for cognitive decline at 6 months was 1.97 compared with those whose EndoCAb levels were higher. For patients younger than 64 years old, the relative risk was 1.06 for those with low EndoCAb levels versus those with higher immunity.

“It is possible that lower immunity in general” influences cognitive decline after CABG, Dr. Mathew told Reuters Health. “But several other studies show that endotoxin influences outcomes in other groups as well. For example, ICU patients who do worse and are ventilated for longer periods of time also have lower levels of antibody to endotoxin.”

Dr. Mathew noted that his group is evaluating additional factors that may be involved in the risk for cognitive decline after CABG.

“Interventions that increase IgM EndoCAb levels or reduce the inflammatory response to endotoxin might improve cognitive function after cardiac surgery,” the Duke University research team concludes.

The group is about to begin a trial in which a protein blocker of endotoxin will be administered prior to CABG to see if it decreases injury related to the procedure. “Another theoretical possibility is a vaccine to boost immunity,” Dr. Mathew added.

Stroke 2003;34:508-513.