Fig. 3

Associations between clinical variables and MRI measurements at the cervicothoracic junction of the spinal cord in the PD_RBD(+) subgroup. (A, C) Spearman’s rank partial correlation matrices (rho coefficients) between clinical variables and averaged T1 relaxation (A) and MD (C) values across the C6-T1 vertebral levels in the PD_RBD(+) subgroup. Asterisks indicate correlations that were significant before correction for multiple comparisons, while symbols in parentheses indicate those that remain significant after FDR correction. Circles specifically denote non-significant trends (p < 0.10). Significance levels are indicated as follows: p < 0.10 (°), p < 0.05 (*), p < 0.01 (**), and p < 0.001 (***). (B, D) Scatterplots with linear regression lines showing significant correlations (after FDR correction) between systolic blood pressure drop values at 3 min (adjusted for age and sex) and T1 relaxation values in the descending tracts (B), as well as MD values in the ascending tracts (D), also adjusted for age and sex, in the PD_RBD(+) subgroup. These correlations were not significant in the PD_RBD(−) subgroup. The shaded area around each regression line represents the 95% confidence interval of the fitted model. Marginal density plots along the top and right margins illustrate the distributions of systolic blood pressure drops at 3 min, T1 relaxation values in the descending tracts (B), and MD values in the ascending tracts (D) for each subgroup, respectively. Raw Spearman’s rho coefficients and p-values without correction are indicated on each plot. Abbreviations: FDR, false discovery rate; MD, mean diffusivity; PD; Parkinson’s disease; PD_RBD(+), PD with RBD; RBD, Rapid-Eye Movement Sleep Behavior Disorder; SCOPA-AUT, SCales for Outcomes in PArkinson’s disease—Autonomic Dysfunction; T1, longitudinal relaxation time.