THURSDAY, July 5 (HealthDay News) -- For patients undergoing cardiac surgery, postoperative development of delirium correlates with a decline in cognitive ability during the first year after surgery, according to a study published in the July 5 issue of the New England Journal of Medicine.

Jane S. Saczynski, Ph.D., from the University of Massachusetts Medical School in Worcester, and colleagues examined postoperative delirium and the cognitive trajectory during the first year after coronary-artery bypass grafting or valve replacement surgery for 225 patients, aged 60 years or older. Participants were assessed preoperatively; on day two after surgery and every following day during hospitalization; and at one, six, and 12 months after surgery. The Mini-Mental State Examination (MMSE) was used to assess cognitive function and the Confusion Assessment Method was used to diagnose delirium.

For the 46 percent of participants in whom delirium developed postoperatively, the researchers identified significantly lower preoperative mean MMSE scores compared with those who did not develop delirium (25.8 versus 26.9). After adjustment, compared with those without delirium, patients with delirium experienced a significantly larger decline in cognitive function two days after surgery (7.7 versus 2.1 points on the MMSE) and significantly reduced cognitive function at one month (mean MMSE score, 24.1 versus 27.4) and one year (25.2 versus 27.2) after surgery. The between-group difference in mean MMSE scores was found to be significant 30 days after surgery but not at six or 12 months, after adjustment for baseline differences.

"Postoperative development of delirium was a risk factor for a decline in cognitive function and a prolonged period of impairment after surgery," the authors write.

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