Published: Jan. 2, 2008
Updated: Nov. 4, 2010
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By Duke Medicine News and Communications
DURHAM, N.C. -- Patients over the age of 60 who have elective surgeries such as joint replacements, hysterectomies and other non-emergency, inpatient procedures, are at an increased risk for long-term cognitive problems, according to a new study led by Duke University Medical Center researchers.
The study also found that elderly patients who developed these postoperative cognitive problems were more likely to die in the first year after surgery.
"We have known that patients undergoing heart surgery are at risk for cognitive dysfunction -- problems with memory, concentration, processing of information -- but the effects of non-cardiac surgeries on brain function are not as well-understood," said Terri Monk, MD, an anesthesiologist at Duke and the Durham Veterans Affairs Medical Center, and lead investigator on the study. "Our study found that increasing age put patients in this population at greater risk for cognitive problems and this is significant because the elderly are the fastest growing segment of the population. We know that half of all people 65 and older will have at least one surgery in their lifetime."
The researchers published their findings in the January 1, 2008 issue of the journal Anesthesiology and the results were published early online on December 27, 2007 on the journal's Web site. The article is accompanied by a supportive editorial and a companion article detailing the types of cognitive dysfunction that developed and the effects on patients' daily lives. The study was funded by the National Institute on Aging, the Anesthesia Patient Safety Foundation and the I. Heerman Foundation.
The researchers measured memory and the ability to process information in more than 1000 adult patients of different ages. Patients were tested preoperatively, at the time of hospital discharge, and three months after surgery. More than 200 control subjects took the same tests at the same frequency, but did not undergo surgery or anesthesia.
The study found that many of the young, middle-aged and elderly patients experienced postoperative cognitive dysfunction (POCD) at the time they left the hospital. But three months later, those aged 60 and older were more than twice as likely to exhibit POCD. Those with POCD at both the time of hospital discharge and three months after surgery also were more likely to die within the first year after surgery, Monk said.
"The large difference in the prevalence of POCD between what we termed the elderly -- those aged 60 and over -- and the younger groups we were studying validates the general perception that the elderly are predisposed to cognitive impairment after major surgery," Monk said. POCD was more common among those patients with lower educational level and a history of a stroke that had left no noticeable neurologic impairment.
"Education protected against postoperative cognitive problems, likely because education may provide an opportunity to condition the brain, and better equip it to withstand injury, much like physical exercise has a protective effect on the body," Monk said.
The reasons why cognitive decline is associated with early death are not completely understood, but it's possible that patients with prolonged cognitive dysfunction might be less able to take medicines correctly or may not recognize the need to seek medical care for symptoms of complications, Monk said.
"Studies on normal aging have shown a link between abrupt cognitive decline and early death, so we speculated that surgery-related cognitive dysfunction might have the same effect," she said.
Why some patients suffer POCD is not known, but one hypothesis is that surgery and the accompanying anesthesia might cause inflammation in the brain that can affect the patient's ability to learn, retain or remember information, Monk said.
Now that the implications of long-term POCD are better understood, doctors must devise strategies to prevent or mitigate the detrimental effects of surgery and anesthesia on the aging brain, Monk said. The types of interventions and how to implement them will be the subject of further research, she said.
Other researchers on this study include B. Craig Weldon of Duke; and Cyndi Garvan, Duane Dede, Maria van der Aa, Kenneth Heilman and Joachim Gravenstein of the University of Florida.