CTSB and Alzheimer disease: In this sub-analysis, cathepsin B activity was significantly different between case types (ANOVA F(2,17) = 6.792, p = 0.007), with activity being significantly higher in EOAD compared with healthy ageing (pairwise comparison with Bonferroni p = 0.008) but not different between AD-DS and healthy ageing (pairwise comparison with Bonferroni p = 1.000) (Additional file 1: Supplementary Fig. 1a).