Table 3.
Stepwise variable selection and multiple regression analyses for important clinical factors that affect nigral iron in PDDT.
| Variable Selected | Multiple regression analysis | ||||
|---|---|---|---|---|---|
| β | SEM | F values | P values | ||
| Age | No | ||||
| Sex | No | ||||
| Dopamine agonists | No | ||||
| Rasagiline | No | ||||
| LEDD | No | ||||
| Disease duration (y) | Yes | 2.09 | 0.8 | 4.58 | 0.035 |
| Levodopa (11 vs. 76) | Yes | 28.4 | 13.3 | 6.52 | 0.013 |
| Selegiline (39 vs. 48) | Yes | -19.0 | 8.6 | 4.89 | 0.030 |
Step-wise variable selection was used to explore potential clinical measures and drug effects that may affect QSM values in the SNc. The factors explored included age, sex, disease duration, levodopa (On-Off), dopamine agonists (On-Off), rasagiline (On-Off), selegiline (On-Off), and levodopa equivalent daily dosage (LEDD). We first indicate whether the factor was selected in the variable selection process and then present the results from the multiple regression analysis with the selected factors.