A new study shows that cognitively normal elderly patients who experience delirium after surgery are three times more likely to suffer permanent cognitive impairment or dementia.

According to researchers, delirium is common in elderly hospitalized patients, affecting an estimated 14 percent to 56 percent of patients. It frequently manifests as a sudden change in behavior, with patients suffering acute confusion, inattention, disorganized thinking, and fluctuating mental status.

Pre-existing cognitive impairment or dementia in patients undergoing surgery are widely recognized as risk factors for post-operative delirium, increasing its likelihood and severity, researchers note.

However, little research has focused on whether delirium itself portends or even accelerates a decline into dementia in patients who showed no previous signs of cognitive impairment.

The new study, published in the British Journal of Anaesthesia, focused on patients over the age of 65 who were assessed as cognitively normal prior to surgery.

Led by Professor Juraj Sprung of the Mayo Clinic in Minnesota, the 10-year study included more than 2,000 patients over the age of 65 enrolled at the Mayo Clinic Study of Aging who were exposed to general anesthesia.

Their cognitive status was evaluated in regular 15-month periods before and after surgery by neuropsychologic testing and clinical assessment.

Out of 2,014 patients, 1,667 were deemed to be cognitively normal before surgery, according to the researchers.

Of the 1,152 patients who returned for follow-up cognitive evaluation, 109 (9.5 percent) had developed mild cognitive impairment or dementia. The study’s findings show that those who had suffered post-operative delirium were three times more likely to be subsequently diagnosed with permanent cognitive decline or dementia.

While previous studies have highlighted cognitive decline in the elderly following post-operative delirium, this study involved a detailed neuro-cognitive assessment identifying those with normal pre-operative cognitive abilities who go on to develop dementia, the researchers point out.

The researchers believe that post-operative delirium could be a warning sign of future permanent cognitive impairment in patients who at the time of surgery were still just above the threshold for registering cognitive decline.

Alternatively, post-operative delirium could itself produce injury, which accelerates the trajectory of decline into dementia, the researchers said.

“Our research shows that delirium after surgery is not only distressing for patients and their families, but also may be a warning that patients could later develop dementia, said Sprung. “We don’t yet know whether taking steps to prevent postoperative delirium could also help prevent dementia, but we need to find out.”

Source: Oxford University Press USA

Increased Risk of Dementia for Patients Who Experience Post-Operative Delirium