COPENHAGEN – Almost half of patients with mild cognitive impairment progressed to dementia within 1 year of undergoing either arthroplasty or coronary angiography, according to a small Australian study.
Baseline cognitive impairment appeared to be the main driver of progression, increasing the risk more than sevenfold – significantly more than age or heart attack, Lisbeth Evered, Ph.D., said at the annual Alzheimer’s Association International Conference.
"After 12 months, 42% met the criteria for dementia," said Dr. Evered, a researcher at the University of Melbourne. "The expected annual progression from mild cognitive impairment [MCI] to dementia would be about 10%-12% per year."
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Her study included 67 patients with a mean age of 70 years. All had MCI at baseline, with a mean score of 23 on the Mini-Mental State Exam (MMSE). They underwent either arthroplasty (26 patients) or coronary angiography (41 patients).
A year after surgery, about 34% of the arthroplasty patients and 46% of the angiography patients had progressed to dementia. Baseline cognitive impairment was the only factor significantly associated with the change.
Postsurgical cognitive decline, both transient and long lasting, is a well-documented phenomenon, with studies going back to the late 1800s. Although the causative link isn’t entirely clear, anesthetics have long been implicated, said Dr. Evered. In animal models, some anesthesia drugs do seem to precipitate an Alzheimer’s-like amyloidosis and tau hyperphosphorylation.
More recent animal data suggest that inflammation might be a powerful influence.
"When a patient has surgery with a general anesthetic, they experience peripheral inflammation," Dr. Evered explained. "In a healthy normal brain, there’s plenty of cognitive reserve, and although there might be some cognitive decline afterward, the person won’t really notice and will certainly recover."
In a vulnerable brain, however, the inflammation may be amplified and may cause significant collateral damage that accelerates cognitive decline. "The problem is, we don’t know why they are vulnerable or what we might do about it," she noted.
The best approach now is to routinely assess cognition before surgery and monitor it afterward, Dr. Evered explained. "Then, the perioperative period is not something occurring in isolation," she noted. "We will be better able to identify those at risk and implement strategies to improve their outcomes."
In a video interview, Dr. Evered and Dr. Brendan Silbert of St. Vincent’s Hospital, Melbourne, discuss the study and its implications.
Dr. Evered had no financial disclosures
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