Briefly, significant positive associations were found for BHBA with NfL and p-Tau in the AD group, with a significant negative association for t-Tau. The ND group exhibited the opposite but non-significant correlations. This disparity in associations may suggest disease-specific patterns in AD. Multiple significant associations were found between the quantified BAs and the classical biomarkers in AD. In short, the neurotoxic GCDCA, GDCA, and the ratio GDCA:DCA were significantly and positively associated with t-Tau in the AD group, the first association in line with a previous work performed in serum from AD . Additionally, a statistically significant negative association was observed between the TDCA:DCA ratio and Aβ1-42, in the AD group, which might be associated with higher cerebral amyloid burden 11 .