Saliva samples from Discovery cohort participants were collected using Oragene kits and DNA was extracted in accordance with the manufacturer’s guidelines (Oragene, Genotek, Toronto, Ontario). In the Replication cohort, DNA was extracted from whole blood. Postmortem brain DNA was isolated using the DNeasy Blood and Tissue kit (Qiagen, Valencia, CA), using a protocol that was modified from manufacturers’ instructions (additional proteinase K and RNase A).
