MAPT and Mental deterioration: Therefore, we examined (a) whether cross-sectional and longitudinal levels of plasma p-tau181 in individuals across the cognitive and clinical continuum differ by sex, (b) whether sex modifies associations of plasma p-tau181 with CSF p-tau181, Aβ deposition, glucose metabolism and tau deposition in the brain, and (c) whether sex modifies the effect of baseline plasma p-tau181 on cognitive decline and progression to AD dementia.