There are “negligible” long-term cognitive effects after major surgery during adulthood, new research has concluded (Anesthesiology 2016;124:312-321).
This finding should help bolster physicians when confronted with older patients balking at surgery out of fear that undergoing anesthesia will cause cognitive and memory issues—preoperative medical conditions and mental functioning likely play a more significant role.
“This study adds an important piece to the very complex research puzzle of potential adverse effects of surgery and anesthesia,” said study author Unni Dokkedal, MScPH, from the University of Southern Denmark’s unit of Epidemiology, Biostatistics and Biodemography, in Odense.
The study analyzed 8,503 pairs of middle-aged (<70 years old) and elderly (≥70 years old) Danish twins. The participants were split into those who had at least one surgery (between 18 and 24 years before the intake cognitive exam) and those who did not have any operations.
The twins who underwent surgery were divided into four groups:
- major surgeries, such as “cardiac, thoracic, laparotomy, central and peripheral vascular and major fracture surgeries”;
- knee and hip replacements;
- minor surgeries; and
- other operations.
The researchers gauged cognitive function using a five-part test. The twins were asked to name as many animals as possible in 60 seconds, complete a forward and backward digit span, and perform an immediate and delayed recall of a 12-item list. Cognitive function was determined using data from two Danish studies: the Longitudinal Study of Middle-Aged Danish Twins and the Longitudinal Study of Aging Danish Twins.
The test results on the twins were then cross-referenced with surgery information collected by the Danish National Patient Registry.
Twins who underwent major surgery scored slightly worse on the cognition test compared with twins who had no surgery. However, the difference, one-tenth of an SD, was of “negligible effect size,” the study found. By way of illustration, one-tenth of an SD translates to 23.5 animals recognized per minute in the surgery group versus 24.2 animals per minute in the nonsurgery group, the researchers noted. There was no difference in the cognitive scores of twins who had undergone minor surgery compared with the nonsurgery group.
There were 1,065 monozygotic and 1,179 dizygotic twins, as well as 4,015 “twin individuals,” either from opposite-sex pairs or twins whose “co-twin” had either died or was not taking part in the study. Only same-sex pairs were included in this study to avoid confounding by sex.
The numbers were further refined by including only pairs with a history of major surgery compared with those who had never had a major operation; that yielded 87 monozygotic pairs and 124 dizygotic pairs for a total of 211.
Twins 70 years of age and older who had knee and hip replacements performed the best on the cognitive tests—even beating the twins who never had surgery. Twins who had undergone three or more major surgeries also were slightly more likely to have lower test scores: about one-fifth of an SD. But that difference may be accounted for by postoperative complications or preoperative health conditions.
“Underlying disease” may be “a major determining factor” when it comes to accounting for the slight variations in cognitive functioning between the surgery and nonsurgery groups, the study noted.
The group of twins who had major operations also was more likely to struggle with severe diseases, and require cardiac and thoracic surgery and laparotomies, researchers found.
Ms. Dokkedal said this study stands out compared with previous research because of its large sample size and ability to tap into an “almost complete record of surgeries since 1977.”
The study’s depth “provides a powerful approach to detect even subtle effects of surgery and anesthesia on the postoperative cognitive functioning of elderly patients,” she added.
The study’s results are important given widespread concern about older patients and cognitive function, noted Peter J. Papadakos, MD, director of critical care medicine and professor of anesthesiology and surgery at the University of Rochester School of Medicine and Dentistry, in New York.
More and more patients are surfing the internet and coming across information that suggests general anesthesia causes memory issues.
“It is a very common question if you do geriatric anesthesia,” Dr. Papadakos said. “This study shows there is no difference in the long-term cognitive functioning.”