Table 3.

Total explained variance (Adjusted R²) and explained variance attributed to the newest added predictor (Adjusted R² change) at each step of the linear regression predicting composite WMH volume.

Regression Step and Predictors	Adjusted R2	Adjusted R2 Change	p-value
Step 1	0.200	0.200	<0.001*
Age	–	–	0.001*
Sex	–	–	0.417
ICV	–	–	0.025*
Step 2	0.336	0.136	<0.001*
RD	–	–	<0.001*
Step 3	0.379	0.043	<0.001*
QSM	–	–	0.018*
Step 4	0.406	0.027	<0.001*
CBF	–	–	0.046*

Covariates alone predicted 20% of the variance. Including RD at step 2 increased the adjusted R² of the model to 0.336. After inclusion of QSM in step 3 and CBF in step 4, the total variance explained in total WMH volume exceeded 40%. The p-values in bold reflect the p-value of the model at the indicated step, whereas other p-values represent the indicated variable when they were first entered into the model.

^*p < 0.05.