Does Anesthesia Promote Memory Loss?


It’s not uncommon for people who undergo general anesthesia during surgery to experience some degree of memory impairment afterwards. This is because anesthetics work by blocking certain parts of the brain responsible for memory formation.

Memory problems are even more common in people over the age of 70 following anesthesia. Symptoms persist for months or years in some patients. Patients with Alzheimer’s disease appear to be particularly at risk of impaired cognition following anesthesia, and some studies suggest that exposure to anesthetics may increase the risk of Alzheimer’s disease.

People over 70 are more at risk

In adults over the age of 70, exposure to general anesthesia and surgery is associated with a subtle decline in memory and thinking skills, according to a new study published in 2018. The study analyzed nearly of 2,000 people and found that exposure to anesthesia after age 70 was linked to long-term changes in brain function.

Although the decline in brain function was small, it may be more pronounced in people with already low cognitive function or pre-existing mild cognitive impairment. In older people whose cognitive impairment is not yet clinically recognized, exposure to anesthesia and surgery may highlight underlying problems with memory and thinking.

We need to be sure that patients considering surgery, and their families, are properly informed that the risk of cognitive dysfunction is possible,” explains the study’s lead author. Additionally, alternative strategies should be discussed with patients before surgery is performed for those deemed to be at high risk. This study provides further reasons for clinicians to begin performing routine cognitive assessments prior to surgery. operation to further assess the risk of exposure.

The authors emphasized that it is not possible to determine whether anesthesia, surgery, or underlying conditions requiring surgery caused the decline.

Source : Schulte PJ et coll. Association between exposure to anaesthesia and surgery and long-term cognitive trajectories in older adults: report from the Mayo Clinic Study of Aging. British Journal of Anaesthesia, 2018.

Anesthesia around the age of 40 does not increase the risk of memory loss

There is no significant link between being exposed to general anesthesia after age 40 and the development of mild cognitive impairment years later, according to an epidemiological study. 

The potential link between on the one hand exposure to anesthesia following surgery and on the other hand cognitive decline and dementia has recently been a matter of debate, with previous findings contradicting those recently published. This new study found no link between exposure to anesthesia and cognitive decline when taking into account the number of exposures or the total cumulative duration of exposure. 

« It is reassuring for the majority of older people who may need surgery to learn that anesthesia and surgery are unlikely to be associated with long-term cognitive decline, » says the lead author of study (David O. Warner, Mayo Clinic, Rochester, Minnesota, USA). 

The researchers looked at Mayo Clinic data from 1,731 residents between the ages of 70 and 89 whose cognitive functions were assessed every 15 months. Medical records (including surgeries with anesthesia) were obtained for each participant after the age of 40. Of these, 536 (31%) developed mild cognitive decline over a period of 4.8 years. No adverse effects of anesthesia were reported in the study. 

Although the current results are « comforting », it is quite possible that people at risk are more vulnerable to anesthesia, in particular the elderly with vascular disorders and who are undergoing vascular surgery. Researchers believe that anesthesia produces an inflammatory state in the brain – called neuroinflammation – which would trigger cognitive impairment in people at risk.

Source : Juraj Sprung et coll. Association of Mild Cognitive Impairment With Exposure to General Anesthesia for Surgical and Nonsurgical Procedures. Mayo Clinic Proceedings, 2016.

Age-dependent effect

A study published in the journal Anaesthesia confirmed that anesthesia can cause long-term damage to brain cells and impair memory.  It’s important to note that these results only apply to older adults.  Younger people tend to recover faster after anesthesia because their brains are better able to adapt to the effects of drugs. 

However, older adults often have weaker immune systems and are more susceptible to infections, which could make them more vulnerable to complications following surgery.  One limitation of this study is that it relied on self-reported information about whether participants had undergone surgery. 

Anesthesia and risk of dementia

In 2016, American researchers reported that exposure to anesthesia was not associated with an increased risk of dementia, and Alzheimer’s disease in particular. This prospective study included nearly 4,000 participants aged 65 and older. This result contradicts that published by the European Society of Anaesthesiology (ESA) in June 2013 which reported a 35% increase in the risk of dementia. 

In order to justify these results, the researchers indicated that some anesthetics would promote the inflammation of neural tissues, resulting in lesions characteristic of Alzheimer’s disease (accumulation of amyloid and tau protein). In this study, the average age of the participants was 75 years old and 62% were women. 632 participants (9%) developed dementia 8 years after follow-up. 

However, there have been no clinical trials to establish a link between anesthetic exposure and the development of Alzheimer’s disease. Therefore, before drawing firm conclusions, it is necessary to conduct additional studies. However, one should be aware of the potential risks and take precautions with vulnerable elderly patients.

Source: Mother G et coll. Alzheimer’s disease and anesthesia. Turk J Med Sci 2015;45(5):1026-33).