Abstract
Background
Previous reports suggest physical activity (PA) may influence cognitive function and Alzheimer's disease risk. Furthermore, numerous animal studies report wheel-running reduces the accumulation of Alzheimer's disease pathology, including brain Ab-amyloid (Ab) and tau. We previously reported a relationship between PA and lower brain Ab burden. The recent advent of tau positron emission tomography (PET) tracers enables us to extend our investigations into the evaluation of the relationship between PA and tau burden.
Methods
Data from 88 cognitively healthy older adults of the Australian Imaging Biomarker and Lifestyle Study were used to evaluate the cross-sectional relationship between PA and tau burden. Self-reported PA was used to categorise participants into low-moderate PA (LMPA; n=40) or high PA (HPA; n=48). All participants also underwent Ab PET imaging with either 18F-flutemetamol or 18F-florbetapir, and tau PET imaging with one of three tau tracers: 18F-AV1451 (n=43), 18F-THK5317 (n=24), or 18F-THK5351 (n=21). Ab-negative controls were used to generate cortical tau z-scores (excluding mesial temporal lobe), allowing the combination of results from the three tracers. A linear regression was undertaken with cortical tau z-score entered as the dependent variable, and PA, age, gender, apolipoprotein E ɛ4 allele, BMI, composite memory score, Ab burden, and a Ab burden*PA interaction term entered into the model.
Results
The LMPA group had higher mean cortical tau burden (z-score:1.87±2.30), compared to the HPA group (z-score:0.57±1.64; F=5.47, p=0.02). A significant interaction was found between Ab burden*PA (F=10.24, p=0.002): Although the expected significant association between tau and Ab burden was found in the LMPA group, there was no association between tau and Ab burden in the HPA group.
Conclusions
Our results indicate high PA is associated with lower brain tau. Given that the association between PA and tau was not altered following adjustment for objective memory function, our results suggest that higher PA alters tau aggregation or deposition. Our results also indicate high PA alters the association between brain Aβ and tau. Future longitudinal and interventional studies are vital to further investigate the relationship between tau, Aβ and PA.