Preexisting Cognitive Impairment and Mild Cognitive Impairment in Subjects Presenting for Total Hip Joint Replacement

Background The prevalence of preexisting cognitive impairment (PreCI) is documented before cardiac surgery, but there is less information before noncardiac surgery. In addition, the prevalence of mild cognitive impairment, defined by different cognitive criteria and subjective complaints, and which may progress to Alzheimer disease, is unknown in these subjects. Because anesthesia and surgery have been implicated in Alzheimer disease pathology, we prospectively measured PreCI and mild cognitive impairment in subjects scheduled for total hip joint replacement surgery in an observational study. Methods One hundred fifty-two subjects 60 y of age and older who were scheduled for total hip joint replacement surgery underwent assessment, including neuropsychologic testing, 1 week before surgery. Test results were compared with published norms. PreCI was defined as impairment in two or more of seven cognitive tests, for which impairment in an individual test was defined as ≥ 2 SD below norms for that test. Amnestic mild cognitive impairment (aMCI) was defined as impairment ≥1.5 SD below norms for results of the immediate and/or delayed Auditory Verbal Learning Test plus a subjective complaint. Results Subjects performed worse compared with normative data on five of seven neuropsychologic tests. Thirty (20% [95% CI, 13-26%]) subjects were classified as having PreCI. Thirty-four (22% [95% CI, 16-29%]) were classified as having aMCI. Ten (7%) subjects were classified as having both PreCI and aMCI, representing 33% of the 30 subjects with PreCI. Conclusions The prevalence of aMCI in subjects scheduled for total hip joint replacement surgery is similar to that in the general community. PreCI and aMCI tend to identify different subjects. Because aMCI is known to progress to Alzheimer disease, future studies that track cognition before and after anesthesia and surgery should document the presence or absence of aMCI so that the rate of conversion to Alzheimer disease after anesthesia and surgery can be compared with the rate in the nonsurgical population.