Finally, we performed hierarchical linear regression to assess the variance in Aβ levels uniquely explained by these genetic factors (ΔR2). Age, gender, and diagnosis were entered as the first block in the model, and collectively accounted for 2.7% of the variance in cortical Aβ levels in this sample. APOE ε4 allele status (+/−) and BCHE rs509208 allele status (+/−) were included in the second block for stepwise entry into the model. APOE ε4 was found to explain an additional 10.7% of the variance, while BCHE rs509208 accounted for 4.3% of variance over and above that explained by the previously entered variables.
