This scientific commentary refers to ‘Plasma total-tau, neurofilament light chain and amyloid-β levels and risk of dementia: a population-based study’ by de Wolf et al. (https://doi.org/10.1093/brain/awaa054), and ‘Relationship of amyloid-b1–42 in blood and brain amyloid: Ginkgo Evaluation of Memory Study’ by Lopez et al. (https://doi.org/10.1093/braincomms/fcz038), two papers that illustrate these latest developments. The gene discussed is MAPT; the disease is dementia.