The incidence of cognitive decline after (not) undergoing coronary artery bypass grafting: the impact of a controlled definition

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Abstract
After coronary artery bypass grafting (CABG), 20-30% of patients are reported to suffer from cognitive decline. Studies reporting these high incidences, however, have not included an appropriate control group. We repeatedly administered a series of neuropsychological tests to 112 healthy middle-aged volunteers not undergoing surgery, and applied two widely used definitions of cognitive decline to their test results. In addition, we re-analysed the neuropsychological test data of 281 CABG patients with a definition of cognitive decline that takes into account the natural variability of test performance that was found in the volunteers. Three months after their first assessment, 14-28% of the volunteers suffered from cognitive decline according to the definitions of cognitive decline after CABG. Using the controlled definition of cognitive decline that takes the natural variability in test performance into account, we found that only 7.7% of the CABG patients suffered from cognitive decline at 3 months after their operation. These data suggest that the incidence of cognitive dysfunction after CABG has previously been greatly overestimated.