SORL1 and Alzheimer disease: To discern whether the apparent rs661057 association with SORL1 expression was independent of AD neuropathology and synaptophysin expression, we analyzed FL-SORL1 expression by using a linear regression model that included rs661057 genotype, synaptophysin expression and Braak stage; since FL-SORL1 expression was similar for individuals with moderate and high Braak stages, these two categories were combined to optimize statistical power.