Gene mutation may explain postoperative delirium

Elderly patients who carry the apolipoprotein E (APOE) e4 allele, a gene mutation implicated in Alzheimer's disease, are at increased risk for experiencing early delirium after surgery, investigators report.

They note that postoperative delirium is common in older patients after noncardiac surgery, and it is associated with prolonged hospital stays and increased rates of nursing home placement. Although it is common and may have serious repercussions, no specific cause has been identified, Dr. Jacqueline M. Leung commented to Reuters Health.

"Our study results suggest that genetic predisposition plays a role and may interact with anesthetic/surgical factors contributing to the development of early postoperative delirium," she added.

Leung, at the University of California, San Francisco, and colleagues conducted a study of 190 patients ages 65 or older who underwent major noncardiac surgery requiring anesthesia. Overall, 15.3 percent developed postoperative delirium on the first or second day after surgery.

DNA analysis showed that 46 patients (24.2 percent) carried at least one copy of the APOE e4 allele.

"The presence of one copy of the e4 allele was associated with an increased risk of early postoperative delirium," the investigators report in the medical journal Anesthesiology.

After accounting for the effects of known demographic and clinical risk factors, APOE e4 carriers had 3.6-times the risk of postoperative delirium compared with non-e4 carriers.

Leung and colleagues recommend further studies to determine how APOE e4, which has previously been associated with increased risk of dementia and cognitive decline, increases the risk of postoperative delirium - and whether patients with postoperative delirium and the APOE e4 allele also have a higher risk for further cognitive impairment.

SOURCE: Anesthesiology, September 2007.