Examination of the use of cognitive domains in postoperative cognitive dysfunction after coronary artery bypass graft surgery.

BACKGROUND: Cognitive domain summary scores have been used to examine postoperative cognitive dysfunction in a number of influential studies. To successfully examine cognitive dysfunction in this way, the domains need to be consistent during the assessment time points or the results are distorted. The current study examines two methods of determining cognitive domains and examines their temporal stability during serial cognitive assessments after coronary artery bypass graft surgery. METHODS: Two hundred and four coronary artery bypass graft patients and 80 matched healthy control subjects 55 years or older completed a battery of neuropsychological assessments at baseline and at 7 days and 3 months. Domains were determined in two ways. The first was based on precedence, and neuropsychological tests were allocated to commonly attributed cognitive domains. The second method was to conduct principal components analysis to statistically determine the domains at each time. The stability of these factors was then assessed over time by conducting repeated analysis. RESULTS: There were discrepancies between the two methods used to determine decline, and among the factors in the control and surgical groups. Stability with time was not evident as the factors varied within the groups. CONCLUSIONS: The assessment of postoperative cognitive dysfunction would be best served by the use of individual test results with efforts made to minimize false-positive classification as the extracted cognitive domains do not appear to be temporally consistent, and were sample specific.