General anaesthesia does not impact brain function

A study found that patient factors such as a history of high blood pressure, type 2 diabetes, smoking, and educational level, have more of a long-term impact on cognitive decline compared to general anaesthesia exposure.

A study into general anaesthesia

Post-operative cognitive decline (POCD) is characterised by impaired memory and concentration and can be temporary or persist anywhere between months to years after admission of general anaesthesia. It was estimated that around one in 10 patients aged 60 and older show some degree of cognitive impairment three months after surgery, although the diagnostic criteria for POCD have not yet been standardised. Therefore, causes and risk factors are still being explored and established.

However, a new study conducted by Dr Christoph Pennings from Maastricht University Medical Center, tracked 1,823 adults aged between 25-84, and found that that patient factors like high blood pressure, type 2 diabetes, and a lower level of education are stronger predictors of long-term cognitive decline than repeated surgery under general anaesthesia.

To discover whether repeated exposure to surgery under general anaesthesia during an individual’s lifetime negatively impacts their natural cognitive decline, Pennings and his colleagues analysed prospective data from 1,823 adults (the average age being 51 years, and 50% of participants being male), with normal cognitive functioning from the Registration Network Family Practices, which is a register that is representative of the Dutch population.

Participants were interviewed at the start of the study, then again after six years, and once more after a further six years. Each meeting included a medical exam, and a battery of cognitive function tests to measure learning and memory, executive function, information processing speed, and selective attention and mental speed. The researchers used modelling to consider the cognitive development of participants following the admission of general anaesthesia and correlated those to everyone’s independent risk factors.

Those who had undergone more than two instances of general anaesthesia by the start of the study tended to be older and have other health conditions such as high blood pressure, coronary artery disease, or high cholesterol (also known as hypercholesterolemia), compared to those who had never had an operation under general anaesthesia.

The researchers adjusted for factors known to be linked with increased risk of cognitive decline, such as, age, sex, educational level, smoking status, alcohol abuse, and other illnesses. After completing this, the researchers found that patients who had received at least one admission of general anaesthetic were significantly more likely to perform poorly on the Stroop test (which assesses a person’s selective attention and mental speed), compared to individuals who had never undergone surgery. However, the number of general anaesthesia admissions did not appear to impact other areas of cognitive function and performance.

Findings

“There is natural continuum of cognitive decline during an individual’s lifetime, so after 12 years almost everyone in the study will have developed some form of cognitive decline. Different individuals cognitively age in different ways—the decline may be sudden or gradual, invalidating, or mild,” explained Pennings.

The findings suggest that having high blood pressure, high cholesterol, type 2 diabetes, a history of smoking, and a low education level had significantly more impact on long-term cognitive decline compared to having an operation under general anaesthesia.

“Our study suggests that repeated exposure to surgery under general anaesthesia has little effect on long-term cognitive decline, with subtle impairments in the ability to focus on specific tasks and how quickly you can process information and make decisions based upon that information,” said Pennings. “Instead, it appears that patient factors such as a history of high blood pressure, diabetes, and educational level are more important for the speed of cognitive decline over an individual’s lifetime. These patient factors seem to be more important, but also better modifiable factors than a necessary operation under general anaesthesia.”

However, the team highlighted that the study was observational and therefore cannot establish cause. They noted that some limitations including limited information on length and type of surgery, specific information on the type of general anaesthesia, and the fact that there was a long follow-up period in which surgical and anaesthetic techniques may have changed over time.

These findings on general anaesthesia are being presented at Euro-anaesthesia, the annual meeting of the European Society of Anaesthesiology and Intensive Care (ESAIC) and could therefore aid efforts to help keep people’s minds sharp as they age.

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