Age effects of coronary artery bypass graft on cognitive status change among elderly male twins

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Abstract
Background: Research regarding long-term cognitive outcome following coronary artery bypass graft (CABG) is inconsistent, which may be due in part to differential genetic and environmental influences within most study samples. Methods: The authors examined the effect of CABG on cognitive status change scores in members of the National Academy of Sciences–National Research Council Twins Registry of World War II veterans. Subjects were administered the modified Telephone Interview for Cognitive Status (TICS-m) at approximately 3-year intervals between 1990 and 2002 as part of an epidemiologic study of dementia. Results: Based on co-twin control analyses using a repeated-measures analysis of variance matching twins discordant for CABG within the pair (n = 464 individuals) across three age categories (63 to 70, 71 to 73, 74 to 83), the authors found at follow-up that men who had CABG between ages 63 and 70 showed an increase in TICS-m scores and performed better than their co-twin who did not have the procedure. No significant differences were found within twin pairs for the older two age groups following CABG surgery. This age effect was replicated when comparing individuals positive for CABG surgery with nonfamilial, age- and education-matched controls who were negative for CABG. Conclusions: In this study of twin pairs who share many genetic and environmental risks for cerebrovascular problems, the results suggest that timing of the CABG procedure may be important to predicting positive cognitive outcomes.