GFAP and early-onset autosomal dominant Alzheimer disease: We investigated how BMI and BV influence BBM concentrations and PET prediction.<h4>Methods</h4>Data from 241 cognitively unimpaired participants in the Alzheimer's Disease Neuroimaging Initiative (ADNI) were examined to evaluate the influence of BMI/BV on BBMs (Aβ<sub>42/40</sub>, p-Tau<sub>181</sub>, p-Tau<sub>217</sub>, glial fibrillary acidic protein [GFAP], neurofilament light chain [NfL]) and BBM-based PET predictions.<h4>Results</h4>Elevated BMI/BV associated with lower BBM concentrations, especially for p-Tau<sub>217</sub> and NfL, independent of brain amyloid burden.