(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, PhD, 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 2 after surgery and every following day during hospitalization; and at 1, 6, 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% 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 vs 26.9). After adjustment, compared with those without delirium, patients with delirium experienced a significantly larger decline in cognitive function 2 days after surgery (7.7 vs 2.1 points on the MMSE) and significantly reduced cognitive function at 1 month (mean MMSE score, 24.1 vs 27.4) and 1 year (25.2 vs 27.2) after surgery. The between-group difference in mean MMSE scores was found to be significant 30 days after surgery but not at 6 or 12 months, after adjustment for baseline differences.

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“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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