Receiving anesthetics, including general anesthesia, can cause memory loss in the long term, according to researchers at the University of Toronto. Multiple studies show that using general anesthetics can result in damage to both memory and attention for a period ranging from months to years, as Scientific American reports.
One 2013 study performed in a Hong Kong hospital found clear evidence of cognitive impairment in patients receiving general anesthesia, as reported by Scientific American. The study compared a group of patients receiving light anesthesia with a group receiving typical and comparatively stronger anesthesia. Cognitive performance, as measured by typical tools such as word-recall tests, showed a difference three months after surgery. Fifteen percent of patients receiving heavier anesthesia had difficulties on the tests, while only 10 percent of those receiving lighter anesthesia had difficulty. Immediate cognitive performance on the first morning after their operation was also markedly different, with 24 percent of patients receiving heavier anesthesia showing signs of confusion compared to only 16 percent of those who received lighter anesthesia.
A study performed in Boston showed that short-term cognitive impairment is a strong indicator of the duration of long-term cognitive effects, as reported by Scientific American. In patients who showed no signs of post-operative delirium, full pre-operative mental capacity returned within one month, but in patients with cognitive impairment that lasted for over three days after the operation, it had not returned a year later. Patients who showed impairment that disappeared in three days or less regained their full capacity within six months to one year.