Objective To examine whether exposure to general anesthesia for operations and procedures after the age of 40 years is associated with incident mild cognitive impairment (MCI) in elderly patients. Patients and Methods A population-based, prospective cohort of Olmsted County, Minnesota, residents aged 70 to 89 years at enrollment, underwent baseline and 15-month interval evaluations that included the Clinical Dementia Rating scale, a neurologic evaluation, and neuropsychological testing. Anesthesia records after the age of 40 years until last evaluation for MCI were abstracted. Proportional hazards regression, adjusting for other known MCI risk factors, was used to assess whether exposure to surgical general anesthesia after the age of 40 years is associated with the incidence of MCI. Results Of 1731 participants (mean age, 79 years), 536 (31.0%) developed MCI during a median follow-up of 4.8 years. Anesthesia exposure was not associated with MCI when analyzed as a dichotomous variable (any vs none; adjusted hazard ratio [HR], 1.07; 95% CI, 0.83-1.37; P=.61), the number of exposures (adjusted HR, 1.05; 95% CI, 0.78-1.42; adjusted HR, 1.12; 95% CI, 0.86-1.47; and adjusted HR, 1.02; 95% CI, 0.76-1.34, for 1, 2-3, and ≥4 exposures compared with no exposure as the reference; P=.73), or the total cumulative duration of exposure (adjusted HR, 1.00; 95% CI, 0.98-1.01, per 60-minute increase; P=.83). In secondary sensitivity analyses, anesthesia after 60 years of age was associated with incident MCI (adjusted HR, 1.25; 95% CI, 1.02-1.55; P=.04), as was exposure in the previous 20 and 10 years. Conclusion We found no significant association between cumulative exposure to surgical anesthesia after 40 years of age and MCI. However, these data do not exclude the possibility that anesthetic exposures occurring later in life may be associated with an increase in the rate of incident MCI.
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