| This empirical review sought to synthesize the existing body of research on the effects of white matter changes of the brain on cognition as evidenced by neuropsychological test performance in healthy adults. Sixteen reports included 3,833 adults who underwent MR imaging and neuropsychological testing. An effect size correlation r was computed for each study and transformed to Fisher's zr to identify relationships among white matter changes and cognition. Global analysis revealed a positive effect size of zr = 0.03 with 95% confidence intervals (upper bound 0.39, lower bound -0.39). This result does not support the hypothesis that white matter hyperintensities on magnetic resonance imaging are associated with a decline in cognitive performance. Moderator variables, such as age, education, and imaging technique were analyzed and none were significant. Post-hoc analyses were performed on cognitive domains of executive functions, processing speed, memory, and attention. None of these outcome categories showed significant effect sizes meaning that WMH burden did not have a differential effect on the above cognitive domains. |
