DNA methylation data for older persons with vs. without mild cognitive impairment

Genome wide DNA methylation assays was conducted using the Illumina Infinium MethylationEPIC BeadArray technology (Methyl850K chip) that allows genome-wide DNA methylation analysis of 866,836 CpG sites. We included baseline and 2-year follow-up samples from 25 persons with mild cognitive impairment (cases) and 20 persons with cognitively normal (controls). Sample was balanced by age and sex. Bisulfite conversion, or bisulfite treatment, whole genome amplification (WGA), hybridization and single base extension were carried out to get labeled nucleotide using standard protocol. Dual color (Cy3 and Cy5) staining was used for allowing the nucleotide to be detected by the iSCAN reader and is converted to genotype during the analysis.