Previous research suggests that surgery in older individuals may harm their future cognitive health. However, researchers from the University of Southern Denmark found that going under the knife, which comes with anesthesia, is not typically associated with long-term impairment.

While postoperative cognitive dysfunction is normal for up to a few weeks following surgery, researchers wanted to see if surgery, anesthesia and the interactions of other potential health complications could influence memory.

"It is important to know whether surgery and anesthesia have any negative effects, especially with regard to preoperative counseling of the patient," Unni Dokkedal, a researcher at the University of Southern Denmark, said. "This research has the potential to become a key piece of this very complex research puzzle."

The study was based on over 8,500 middle-aged and elderly Danish twins. About half of the participants were younger than 70 and half were older than 70.

The researchers compared cognitive tests from the twins who had surgery with anesthesia for a major or minor hip or knee surgery between 18 and 24 years before the study began.

Findings did show that twins who underwent major surgery had slightly lower scores when compared to counterparts who did not. However, researchers noted that the score differences between the groups were not statistically significant. Furthermore, they found that this was even true for participants with surgeries completed anywhere from three months to two years before the study's start--further suggesting that anesthesia had little effect on memory beyond a few weeks following the immediate procedure. 

In an accompanying editorial, author Michael S. Avidan, M.B., B.Ch. and Alex S. Evers, M.D., Washington University School of Medicine in St. Louis noted that older patients who need surgery should feel reassured by the findings.

"On the basis of a growing body of evidence, of which the study by Dokkedal et al. is symbolic, older patients should today be reassured that surgery and anesthesia are unlikely to be implicated in causing persistent cognitive decline or incident dementia," Avidan said. "The large number of patients and the use of rigorous longitudinal cognitive testing in the study increased the reliability of the findings."

The study was published today in the journal Anesthesiology.