Myelin water fraction, diffusion tensor imaging, and g-ratio measurements characterize myelin changes in normative aging, mild cognitive impairment, and dementia

In previous work, we showed evidence of myelin loss with mild cognitive impairment (MCI) using a direct and specific MRI measure of myelin water fraction, a surrogate for myelin content. Here, we extend this by investigating changes in myelin content in normative aging, MCI, and dementia using myelin content, diffusion tensor imaging, and g-ratio measurements. Our results showed decrease in myelin content in several brain regions of the subjects diagnosed with MCI or dementia in comparison with the old healthy subjects. Higher myelin content in middle-aged subjects was also observed, in agreement with the literature.