We then examined the trajectory of total hippocampal volume across age by APOE genotype using a model‐free sliding‐window approach, which does not assume a linear relationship between the variables. We used a sliding interval of 1 year and a window length of ± 5 years. Mean volumes were calculated within each window and plotted as a function of age along with 95% confidence intervals. This procedure was performed separately on raw hippocampal volume and residual volume after regressing out covariate effects.
