According to standard procedures, ethylenediamine tetra-acetic-treated (EDTA) plasma was sampled, aliquoted, and frozen at − 80 °C. From plasma samples collected between 2002 and 2005, NfL measurements were assessed in two separate batches (5094 measurements) on a single molecule array (Simoa) HD-1 analyzer platform [19 (link)] with the NF-light advantage kit [20 (link)] at Quanterix (Lexington, MA, USA). The first batch of 2000 samples was obtained from a random selection of 1000 participants from the fourth visit of RS-I and 1000 from the second visit of RS-II. The second batch of 3094 samples was obtained from the remaining participants of these two study waves. Samples were tested in duplicate, and on each plate, two quality control samples were run. NfL was measured with the NF-light advantage kit [20 (link)]. The coefficient of variation for all available plasma samples is published elsewhere [3 (link)]. Participant’s data were excluded from the analyses when the concentration coefficient of variation exceeded 20%, when control samples were out of range, or when the duplicates or single measurements were missing.
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