| Neuropsychological functioning is negatively affected in many individuals who undergo coronary artery bypass grafting (CABG). However, the degree and consistency of this impairment is variable. Research in the fields of Alzheimer's disease and HIV suggests that the impact of various assaults to the central nervous system may be mediated through some form of cognitive reserve. The concept of cognitive reserve (CR) is based on the hypothesis that an individual's genetic make-up or experiences acquired throughout life, such as educational and occupational attainment, provide a reserve which allows an individual to sustain greater cerebral injury before clinical presentation of dysfunction. The present study examined whether greater CR may protect against neuropsychological dysfunction among CABG patients. Participants included forty-seven ( N = 47) individuals who underwent elective, normothermic CABG surgery. Participants were placed in high (n = 24) or low ( n = 23) CR groups based on estimated premorbid intelligence and occupational attainment. All were administered a comprehensive battery of neuropsychological tests preoperatively and postoperatively. Results indicated that 59.5% of participants experienced postoperative cognitive decline, with the most notable declines demonstrated in attention, psychomotor speed, and delayed verbal memory. Compared to the low CR group, the high CR demonstrated a greater decline in performance from baseline to post test. Predictors of postoperative decline included higher estimated premorbid intelligence and greater surgical intervention. These data support a threshold model of cognitive reserve theory and suggest that cognitive reserve may mediate the differential impact of surgical intervention on postoperative outcome. |
