Extended Data Fig. 3: Interactive association between cross-sectional Aβ and initial ITC tau burdens on baseline physical activity.

Linear regression model revealed no significant interaction between cross-sectional Aβ and ITC tau burdens on baseline physical activity (Aβ*ITC tau: β = -0.04 [-0.15 to -0.07], p = 0.44), adjusting for age, sex, years of education, and time interval between study baseline and first tau scan. There were further no significant independent effects of Aβ or ITC tau on baseline physical activity (Aβ: β = 0.10 [-0.07 to 0.28], t = 1.16, p = 0.25; ITC tau: β = 0.01 [-0.21 to 0.22], p = 0.96). Statistical significance was assessed using two-tailed t-tests, with p < 0.05 considered statistically significant without adjustment for multiple comparisons. Physical activity (mean steps per day) was square-root transformed prior to model entry, but non-transformed mean steps per day was used to plot the model result to enhance interpretability. Baseline Aβ burden was modeled as a continuous variable. To visualize the model results, the estimated means steps per day across the range of initial ITC tau burden at representative levels of low versus high baseline Aβ burden are presented. Error bands represent the 95% confidence intervals for the estimated mean steps per day. Low and high Aβ are represented, for illustration purposes, by the mean Aβ burden of Aβ-negative (PiB PVC-DVR 1.17) and Aβ-positive (PiB PVC-DVR 1.85) participants respectively. Aβ = beta-amyloid; DVR = distribution volume ratio; ITC = inferior temporal cortex; PVC = partial volume correction; SUVR = standardized uptake value ratio.