Children who underwent general anesthesia for surgery before the age of 4 were found to have poorer intelligence and language development.
Lead study author Dr. Andreas Loepke, of the Department of Anesthesiology at Cincinnati Children's, and colleagues publish their findings in the journal Pediatrics.
In past research, Dr. Loepke and colleagues found that general anesthesia led to nerve cell death and cognitive impairment in mice and rats, which sparked concern about how general anesthesia may impact the human brain in early life - a crucial neurodevelopmental period.
As such, the team set out to assess how general anesthesia given to children undergoing surgery before the age of 4 years may affect brain structure, IQ and language development.
"The ultimate goal of our laboratory and clinical research is to improve safety and outcomes in young children who have no choice but to undergo surgery with anesthesia to treat their serious health concerns," says Dr. Loepke.
"We also have to better understand to what extent anesthetics and other factors contribute to learning abnormalities in children before making drastic changes to our current practice," he adds, "which by all measures has become very safe."
Anesthesia before age 4 linked to lower gray matter density in cerebellum, occipital cortex
The researchers enrolled 53 participants aged 5-18 years who had undergone surgery involving general anesthesia before the age of 4, alongside 53 age-matched participants who had not had surgery.
None of the children had a history of neurologic or psychological illness, according to the team, and none had experienced traumatic brain injuries.
Magnetic resonance imaging (MRI) was used to analyze the children's brain structures, and the children were also required to complete IQ and language development tests, including the Oral and Written Language Scales and the Wechsler Intelligence Scale.
While all children's test scores were within the normal range in comparison with the general population, the team found that those who underwent surgery had much lower IQ and language development scores than those who had not had surgery.
What is more, the researchers found that the lower test scores among the children who underwent surgery were mediated by reduced gray matter density in the occipital cortex and cerebellum of the brain.
These findings remained after accounting for potential confounding factors, including children's age, gender, socioeconomic status, left or right handedness, the type of surgery performed and the length of exposure to anesthetics.
Lower IQ scores may equate to lifetime earnings loss of $560 billion
According to the researchers, the lower IQ scores identified among children who received general anesthesia for surgery is the equivalent to a potential loss of around a 5-6 IQ points.
They note that this finding could have important implications for society, pointing to one previous study that estimated every 1-point IQ loss may reduce a person's lifetime earnings potential by $18,000.
The researchers calculate that among the 6 million children who undergo surgery in US each year, a 5-6-point loss in IQ could equate to a potential lifetime earnings loss of $540 billion.
The team notes that their findings emphasize the importance of finding better ways to administer anesthesia to young children undergoing surgery - something they are currently investigating in laboratory studies.
However, they stress that current anesthesia techniques are very safe and that the benefits of surgery for young children far outweigh the risks associated with anesthetic exposure.
"It is important to note that no surgeries are truly elective in young children," Dr. Loepke notes. "Many surgical procedures early in life treat life-threatening conditions, avert serious health complications, or improve quality of life. These cannot be easily postponed or avoided."
In June 2014, Medical News Today reported on a study published in the Proceedings of the National Academy of Sciences, which provided insight into what happens to the human brain as it recovers from the effects of general anesthesia.
The research team - including Andrew Hudson of the University of California-Los Angeles - found that the brain has to go through a series of certain states, or "way stations," in order to recover from anesthetic.
"We found that certain states act as hubs through which the brain must pass to continue on its way to consciousness," Hudson explains.