Lower myelin content is associated with more rapid cognitive decline among cognitively unimpaired individuals.

Abstract

The influence of myelination on longitudinal changes in cognitive performance remains unclear. For each participant (N=123), longitudinal cognitive scores were calculated. Myelin content was probed using myelin water fraction (MWF) or longitudinal relaxation rate (R1 ); both are MRI measures sensitive to myelin, with MWF being specific. Lower MWF was associated with steeper declines in executive function (p<.02 in all regions) and lower R1 was associated with steeper declines in verbal fluency (p<.03 in all regions). Additionally, lower R1 was associated with steeper declines in executive function (p<.02 in all regions) and memory (p<.04 in occipital and cerebral white matter) but did not survive Bonferroni correction. We demonstrate significant relationships between myelin content and the rates of change in cognitive performance among cognitively normal individuals. These findings highlight the importance of myelin in cognitive functioning and suggest MWF and R1 as imaging biomarkers to predict cognitive changes.