Participants with both anemia and high p-tau217, NfL, or GFAP had the highest hazard of dementia (eg, adjusted HR of 3.64 [95% CI, 2.39-5.56] among those with anemia and high NfL).<h4>Conclusions and relevance</h4>In this cohort study of dementia-free older adults, anemia was associated cross-sectionally with higher levels of AD blood biomarkers and longitudinally with increased dementia risk. Here, GFAP is linked to anemia (phenotype).