Objective
To examine whether exposure to general anesthesia for surgeries and procedures after the age of 40 is associated with incident mild cognitive impairment (MCI) in the elderly.
Patients and Methods
A population-based prospective cohort of Olmsted County, MN, residents ages 70-89 years on October 1, 2004, underwent baseline and 15-month interval evaluations that included the Clinical Dementia Rating scale, a neurologic evaluation, and neuropsychological testing. Anesthesia records after age 40 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 is associated with the incidence of MCI.
Results
Of 1,731 participants (mean age 79), 536 (31%) developed MCI during median 4.8 years follow-up. Anesthesia exposure was not associated with MCI when analyzed as a dichotomous variable (any vs. none, adjusted HR 1.07 [95% CI 0.83-1.37]; P=.61), the number of exposures (adjusted HR = 1.05 [0.78-1.42], 1.12 [0.86-1.47], and 1.02 [0.76-1.34] for 1, 2-3, and ≥4 exposures compared to no exposure as the reference; P=.73), or as the total cumulative duration of exposure (adjusted HR =1.00 [0.98-1.01] per 60 min increase, P=.83). In secondary sensitivity analyses anesthesia after age 60 was associated with incident MCI (adjusted HR =1.25 [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 age 40 and MCI. However, these data do not exclude the possibility that anesthetic exposures occurring later in life may be associated an increase in the rate of incident MCI.