GFAP and infection: Consistent with these suggestive PET findings, three of the five infections of interest were associated with significantly lower plasma levels of Aβ42/40 (indicative of higher brain Aβ), including influenza (β = −0.01, p = 0.011; also related to higher pTau-181 [β = 0.36, p = 0.018] and GFAP [β = 0.07, p = 0.035]), miscellaneous bacterial infections (β = −0.24, p = 0.029; also related to higher pTau-181 [β = 0.38, p = 0.003]) and UTIs (β = −0.20, p = 0.043; also related to higher GFAP [β = 0.22, p = 0.015]; Fig. 4B; Supplementary Table 11).