Results of a large twin study showed no clinically significant association between general anesthesia and long-term cognitive decline, suggesting that other factors may influence postoperative cognitive dysfunction (POCD).
The results were published in Anesthesiology, the journal of the American Society of Anesthesiologists.
Post-op cognitive impairment, including POCD and delirium, are common in all ages, however elderly patients are at an elevated risk. Previous studies have shown that impairment is still detectable 3 months post-op in patients older than 60 years, and may be present for more than 6 months, impacting overall quality of life and mortality risk. It is still unclear what role, if any, surgery, pre-existing conditions, and other factors play.
In this study, researchers led by Unni Dokkedal, MPH, of the University of Southern Denmark, examined the association between exposure to surgery and level of cognitive function in a sample of 8503 twins — 4299 under 70 years old and 4204 aged 70 years or older. Sixty-five percent of participants had at least 1 surgery prior to intake cognitive examination.
Cognitive tests from twins who had major, minor, hip and knee replacement, or other surgery within 18 to 24 years before cognitive examination were compared to a reference group of twins with no history of surgical procedures. These were also compared in intrapair analysis to assess the role of genetics and shared environment.
Twins who had major surgery had slightly lower cognitive scores compared to the reference group when adjusted for sex and age (mean difference, −0.27; 95% CI, −0.48 to −0.06). When this group was compared to their twin, accounting for genetic and shared environmental factors, the association was not statistically significant. No differences were found in the minor or other surgery groups when compared to the reference group.
Interestingly, twins who had undergone hip and knee replacement surgery had marginally higher cognitive scores (mean difference, 0.35; 95% CI, −0.18 to 0.87), but this was not significant. No association between surgery and cognitive function was found in patients who had undergone surgery in 3 months to 2 years prior to cognitive examination.
“Our use of twins in the study provides a powerful approach to detect subtle effects of surgery and anesthesia on cognitive functioning by minimizing the risk that the true effects of surgery and anesthesia are mixed up with other environmental and genetic factors,” said Dokkedal. “We found no significant cognitive effects related to surgery and anesthesia in these patients, suggesting that other factors, such as preoperative cognitive levels and underlying diseases, are more important to cognitive functioning in aging patients following surgery.”
The authors feel that this research may help put many older patients at ease when facing surgery and anesthesia. To further this effort, the American Society of Anesthesiologists is launching a patient safety initiative to develop best practices, foster understanding, and increase awareness of POCD and delirium.