APOE genotyping was performed on blood samples from all patients and control individuals. Fresh whole blood was drawn into 6 mL EDTA-vacutainers, and DNA isolated using the QIAamp DNA Blood Mini Kit (QIAGEN), together with the spin protocol provided. Random samples of isolated DNA were checked for purity using NanoDrop technology, and all samples were frozen and stored at −80°C. APOE analysis was either performed according to the protocol described elsewhere5 (link) or using the Fast Start DNA Master HybProbe Kit (Roche) in combination with the LightMix ApoE C112R R158C kit from TiB MolBiol (Berlin, Germany) according to the manufacturer's instructions, followed by APOE genotyping with LightCycler technology (Roche).