To evaluate, in cognitively normal adults, the associations between five platelet indices—plateletcrit (PCT), platelet count (PLT), mean platelet volume (MPV), platelet distribution width (PDW), and platelet large cell ratio (PLCR)—and CSF AD biomarkers (Aβ42, Aβ42/Aβ40, P-tau/Aβ42, T-tau/Aβ42), and to examine effect modification by age and the robustness of findings.

We included 1,047 cognitively normal participants from the CABLE study (mean age 58.33 years; 41.5% female; mean education 9.58 years). Multiple linear regression models assessed associations of platelet indices with CSF biomarkers, adjusting for age, sex, education, and APOE ε4 status. Interaction, stratified (mid-life vs late-life), and sensitivity analyses were conducted.

Platelet indices—particularly PCT—show potential associations with CSF AD pathology markers in cognitively intact adults. Further studies, including longitudinal and causal analyses, are needed to validate and elucidate underlying mechanisms and clinical implications.