Fig. 3
Relationship between disease duration and brain volumes in MS. Scatter plots show the relationship between disease duration and brain volumes (NBV, NCGMV, NDGMV, normalized thalamic volume, or NWMV; a–e) in Japanese (black dots) and Caucasian patients (gray dots). The solid lines represent the linear regression of the data. A test of homogeneity of slopes shows significant differences in NDGMV and normalized thalamic volume between the groups (p = 0.001 for both), and a statistically different trend in NBV between the groups (p = 0.06). A test of homogeneity of intercept demonstrated that NBV, NWMV, NDGMV, and normalized thalamic volume were consistently smaller in Japanese versus Caucasian patients throughout the entire disease duration examined (p = 0.046, p = 0.005, p = 0.01, and p = 0.04, respectively), while NCGMV was similar between the two racial groups in the early course of the disease. R2 = coefficient of determination