Fig. 1

Sex differences in CSF p-Tau by APOE4 status before and after adjusting for testosterone levels. Using multiviariable linear regression, we found a significant sex by APOE4 status interaction on p-Tau levels revealing higher p-Tau levels in women versus men among APOE4 carriers (women: n = 34, mean = 43.16, SD = 2.97; men: n = 59, mean = 32.00, SD = 2.23) but not among APOE4 non-carriers (women: n = 25, mean = 22.61, SD = 2.65; men: n = 54, mean = 28.70, SD = 1.76). The significant sex difference in p-Tau levels among APOE4 carriers was eliminated when adjusting for testosterone levels in addition to relevant covariates. CSF cerebrospinal fluid, p-Tau phosphorylated Tau, APOE4 apolipoprotein E ε4 allele. Relevant covariates were age, education, BMI, and self-reported history of cardiovascular events. Testosterone represents plasma-based total testosterone levels