Increased risk of dementia in people with previous exposure to general anesthesia: A nationwide population‐based case–control study

BACKGROUND: Dementia, which leads to disability, is one of the important diseases occurring among older populations. However, the exact mechanism of the disease remains unknown. The potential risk factor of general anesthesia (GA) in the development of dementia is a controversial topic. Therefore, this study aimed to evaluate the association between previous exposure to different GA types and the incidence of dementia. METHODS: Using the claims data of 1 million insured residents covered by Taiwan's universal health insurance from 2005 to 2009, 5345 newly diagnosed dementia patients older than 50 years were eligible for the study group. The control group, which consisted of 21,380 individuals without dementia, was matched for age, gender, and index date. GA was categorized into three subtypes: endotracheal tube intubation general anesthesia (ETGA), intravenous injection general anesthesia (IVGA) or intramuscular injection general anesthesia (IMGA), and heavy sedation. The multiple logistic regression model was used for analyses. RESULTS: Individuals exposed to surgery under ETGA (odds ratio OR, 1.34; 95% confidence interval CI, 1.25-1.44) and those exposed to surgery under IVGA or IMGA (OR, 1.28; 95% CI, 1.14-1.43) were at significantly higher risk of dementia in a dose-response relationship (P < .0001), whereas surgery under heavy sedation was not associated with increased risk of dementia (OR, 1.04; 95% CI, 0.68-1.59). The dementia risk for subjects with diabetes mellitus who received surgery under ETGA (OR, 1.59; 95% CI, 1.42-1.78), hypertension (OR, 1.98; 95% CI, 1.78-2.21), atherosclerosis (OR, 1.35; 95% CI, 1.22-1.50), or after having experienced a stroke (OR, 3.52; 95% CI, 3.13-3.97), but no interaction was found between surgery under ETGA and depression for the risk of dementia. CONCLUSIONS: A history of previous exposure to surgery under GA might be associated with an increased risk of dementia, particularly in subjects who have undergone repeated exposure to GA. In addition, subjects who had received surgery under ETGA with comorbidities such as stroke, hypertension, diabetes mellitus, and atherosclerosis could have a potential relationship with dementia risk.