Fig. 2: Correlation heatmap showing relationships between REMs variables, clinical measures, cognitive performance, heart rate variability (HRV), and gait and TUG parameters under single-task and dual-task conditions.

Gait variables are categorized into three domains: pace, rhythm, and variability. Correlation strength is indicated by color, with blue representing negative correlations and red representing positive correlations. Significant associations at p < 0.05 are annotated with their corresponding r-values. Analyses were based on different sets of available participant data: REMs, clinical, and cognitive measures (n = 74); HRV (n = 52); and gait (n = 67). See Table 2 for the summary statistics. All correlations are adjusted for age. REMs rapid eye movements, std standard deviation, CV coefficient of variation, MoCA Montreal Cognitive Assessment, TMT Trial Making Test, NN normal-to-normal heartbeat interval, SDNN standard deviation of NN, HF high-frequency power normalized units (HFnu) were calculated as HF/(HF + LF)*100, LF/HF low frequency to high-frequency ratio, str stride, TUG Timed Up and Go test, reg regularity, DT dual-task (performing a cognitive task of serial subtraction of 3), dur duration.