Single gene analysis for differential expression of mRNA and miRNA transcripts was performed in the Number Cruncher Statistical Software (NCSS) v9, using a robust multiple regression model. Prior to the main analyses, a step-wise regression analysis was performed to assess the impact of smoking and liver and brain pathology on expression (as these covariates could not be effectively matched). Only measures significant at a nominal p<0.05 were included as covariates in the regression model to evaluate dependence of gene expression on AD case-status. Smoking was the only covariate with a systemic effect on mRNA expression, and was included as covariate in the robust multiple regression analysis.
