General Anesthesia May Raise Risk of Dementia

A history of surgery with anesthesia may raise the risk of dementia for some patients, particularly those who have been repeatedly exposed to general anesthesia (GA), say researchers from China Medical University in Taichung, Taiwan.

Their study of 26,725 patients, including 5,345 newly diagnosed with dementia and a 21,380 person control group of patients without dementia, evaluated the effects of 3 types of GA: endotracheal tube intubation (ETGA); intravenous injection (IVGA) or intramuscular injection (IMGA); and heavy sedation. The patients were also divided into subgroups: a group of high-risk patients who underwent cardiac, orthopedic, or emergency surgery; moderate-risk patients who underwent general surgery, neurosurgery, gynecologic surgery, cosmetic, rectal, thoracic, or digestive surgery; and patients who underwent other surgeries, such as dental. Patients who did not receive anesthesia were grouped as with or without surgery.

Of the patients with dementia, 32% were exposed to ETGA and 9.3% were exposed to IVGA or IMGA. Exposure to both types of anesthesia was higher in the patients with dementia. Nearly 0.5% of the total sample was exposed to heavy sedation.

The patients who were exposed to ETGA, IVGA, or IMGA had a higher risk of dementia after the researchers adjusted for age, sex, depression, diabetes, hypertension, stroke, and atherosclerosis, all of which were also independent, significant risk factors for dementia. Patients who had been exposed 2 or more times to GA had the highest risk of developing dementia. Heavy sedation was not associated with increased risk.

The relationship between surgery with GA and dementia is complex, the researchers say, because patients who receive anesthesia all undergo surgery. Hospitalization has been associated with the development of dementia, with multiple potential mechanisms. Surgery and GA may play individual or synergistic roles in the development of dementia, with the risk heightened by a patient’s comorbidities.

Further, the researchers say, the inhalation of general anesthetics may have neurotoxic effects that correlate with dementia. The major pathologic hallmark of Alzheimer dementia (AD) is excessive accumulation of amyloid beta (Aβ) protein in the brain. Exposure to inhalational general anesthetics may promote AD processes by inducing apoptosis and Aβ generation.

If surgery with general anesthesia is unavoidable, the researchers advise using less-toxic anesthetics, particularly in elderly patients with systemic vascular comorbidities.

Source
Chen C-W, Lin C-C, Chen K-B, Kuo Y-C, Li C-Y, Chung C-J. Alzheimers Dement. 2014;10(2):196-204.
doi: 10.1016/j.jalz.2013.05.1766.