ABSTRACT :
Preclinical studies consistently associate body temperature with tau phosphorylation in the brain. This study examined the relationship between body temperature taken at lumbar puncture (LP) and CSF pTau181 levels in 142 cognitively healthy PREVENT-AD participants (≥55 years, 39 men, 103 women) at high AD risk due to family history. CSF was collected via LP at baseline/follow-up with prior oral temperature measurement. Levels of pTau181, total tau, and amyloid-β peptide 42 (Aβ₄₂) were quantified, and Spearman correlations were performed to assess their relationship with body temperature, age and sex. No significant correlation was observed between body temperature and pTau181 levels, nor with pTau181/total tau or pTau181/Aβ₄₂ ratios. However, age correlated positively with pTau181 levels (r = 0.21, p < 0.0001) and with the pTau181/Aβ₄₂ ratio (r = 0.17, p < 0.001), particularly in women (r = 0.23, p < 0.0001). These findings suggest that, under standard clinical conditions and within a narrow range of temperatures, routine oral body temperature measured at the time of LP is unlikely to represent a source of pre-analytical variability for CSF pTau181 measurements in at-risk AD individuals.