Increasingly, research finds that exposure to anesthesia in early childhood may have long-term effects on kids’ brain development.
One 2011 study linked exposure to anesthesia to learning disabilities, finding that exposed kids had lower scores on standardized tests of reading, writing, math and reasoning, and were more likely to have behavioral issues at school. Another study in 2012 found that children who underwent multiple exposures to anesthesia early on were twice as likely to be diagnosed with attention deficit/hyperactivity disorder as teenagers, compared with children with fewer exposures to such drugs.
However, these previous studies relied on secondary measures of neuropsychological functioning, such as academic scores, standardized test results, medical records and parent and teacher surveys. They also found associations between anesthesia and long-term risks only in children who had had multiple exposures. Meanwhile, other studies examining the issue failed to show any association at all.
So, Dr. Caleb Ing, an anesthesiologist at Columbia University, and his colleagues took a closer look. They studied 2,868 children born between 1989 and 1992 in western Australia, 321 of whom had had surgical or diagnostic procedures before age 3 and had therefore been exposed to anesthesia. After adjusting for other factors that could contribute to cognitive deficits as measured by standardized tests, the researchers found that children who had received anesthesia early in life were 87% more likely to show language disabilities and nearly 70% more likely to have cognitive problems — assessed using direct neuropsychological tests — at age 10, compared with those who had not been exposed to anesthetic drugs. What’s more, even a single exposure to anesthesia was associated with increased risk.
Ing and his team were particularly interested in whether anesthesia was affecting overall brain development or just certain brain functions, so they administered specific tests gauging visual tracking, non verbal intelligence and language skills, such as grammar and verbal memory. “We used six different tests that looked at language, reasoning, behavior and motor skills that were directly administered by trained researchers,” says Ing. “What we found was that not all parts of the brain are uniformly affected. Language and abstract reasoning were more affected, and behavior and motor skills were not.”
Ing is quick to point out, however, that the results do not necessarily suggest a cause-and-effect relationship between exposure to anesthesia and learning disabilities. While the exposed children showed deficits in language and reasoning, the researchers were not able to determine whether that effect was due to the anesthesia or to the underlying medical condition that required surgery in the first place. But Ing notes that anesthesia was the likely influence on brain development, since most of the infants who were exposed had had relatively minor procedures, including tonsillectomy, insertion of ear tubes to drain infections and circumcision; only a small percentage needed operations for more serious heart problems or neurological conditions.
Still, says Ing, “At this point there is not enough evidence to show a causal link between anesthesia and deficits. It’s concerning in the sense that we should continue to pursue research to answer this question. I don’t think we should change our practice; we still need to do a lot more research before causing too much alarm.”
The link between anesthesia and learning deficits was first discovered in studies of lab rats, which showed problems in learning and memory tasks after exposure. The effect seemed to be strongest in younger rodents, suggesting a window of vulnerability during which the drugs can be particularly harmful for development. Whether that effect can be translated to humans isn’t clear yet. It may be that anesthetic agents have specific effects on certain neurons or brain chemicals, particularly those involved in language and reasoning, but, says Ing, “We’re not exactly sure at this point why certain things in humans are affected.”
Those same animal studies may also provide direction for counteracting the possible effects of the drugs. Rats that were placed in enriched environments in which they were stimulated to learn new skills and to reinforce memory and reasoning tasks (such as in mazes) after anesthesia seemed to perform better on later tests of such skills than animals that were not placed in such an environment.
That suggests that young children who are encouraged to speak and perform skills tasks may be able to make up for any cognitive deficits from their anesthesia exposure as well. There’s no scientific evidence that it would work in humans, but Ing notes that enriched environments have other benefits for learning. “I can’t imagine that trying to enrich and expose a child to more learning opportunities is a bad thing,” he says.
Meanwhile, doctors aren’t advising parents to turn down surgery or anesthesia if their baby needs it. For parents who are worried about their long-term risks, it’s worth asking the doctor about the necessity of the operation. But in most cases, the surgery will be medically necessary — doctors don’t typically recommend procedures for infants unless they have to — and the benefits of surgery will outweigh the still unproven risks of anesthesia.