For their paper, researchers from the University of Wisconsin - Madison (UWM) School of Medicine and Public Health looked at data they collected from the Wisconsin Registry for Alzheimer's Prevention, or WRAP. WRAP involves a cohort of middle-aged people averaging 54 years in age who were given a battery of psychological and cognitive tests over a period of time in order to pinpoint their disease progression.
The UWM team looked specifically at 312 people who had previously undergone one or more surgeries that involved the use of general anesthesia. They then compared what they observed in this group to 652 other patients who had not previously had surgeries with anesthesia, excluding all patients who had had neurological or heart surgeries, as these procedures in and of themselves can directly affect cognitive performance.
All of those evaluated, regardless of surgery and anesthesia status, had reportedly registered as being cognitively normal at the beginning of the study. So any and all deviations the team observed among these individuals at the end of the study could be traced back to the variations in how they were treated prior to surgery.
What was found is that, on average, patients who go under general anesthesia prior to surgery experience minor declines in their immediate memory over the following four years. Meanwhile, those who don't undergo anesthesia tend to have the same memory capacity post-surgery that they had prior to surgery.
Furthermore, the longer a patient spent under general anesthesia, the greater the degree of cognitive decline – or what has been described as "executive functioning," which includes skills like planning and focusing.
At the same time, the changes were still found to be small regardless. In one instance, a patient who received anesthesia prior to surgery experienced a one point drop in immediate memory, and this out of a total of 30 possible points.
"The evidence is increasing, albeit indirect, that there is, at the time of surgery, a combination of factors that lead to a reduction in cognitive performance," stated Dr. Beverly Orser, a professor of physiology and anesthesia at the University of Toronto, who was not involved in the study.
While not all studies agree, many do suggest that anesthesia is dangerous for the human brain
As convincing as all the data turned out to be, however, it is still not possible to definitively peg the memory declines on anesthesia. There are many complex factors at play during surgery, not to mention the unique makeup of patients who are affected differently by extreme medical procedures such as those that involve anesthesia.
One example of this is the barrage of inflammatory chemicals like cytokines that is released when a person breaks a limb. In the event that these chemicals make their way into the brain, the natural consequence is that the sufferer will probably experience some cognitive abnormalities as a result.
There have also been previous studies on this subject that have arrived at conflicting results. One paper published back in 2016, also in the journal Anesthesia, observed significant post-surgery declines in cognitive ability among older adults – especially those with pre-existing memory problems.
Another paper published in the journal JAMA Neurology found a direct link between markers of anesthesia chemicals in the brain and cognitive damage, suggesting that the drugs do, indeed, cause health problems.
Still another study, though, published around the same time somewhere else, found a negligible difference in cognitive ability between elderly and middle-aged twins, one of whom had undergone surgery and the other whom had not.
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