Table 4.
Variable importance (VIMP) and relative variable importance (RVIMP) values from conditional Random Forest algorithm (100,000 trees) of each candidate clinical, demographical, pathological, treatment, and coffee/tea consumption variables in explaining the variability of the ΔFS (log values).
| Rank | Variable | VIMP | RVIMP |
|---|---|---|---|
| 1 | Age at onset | 0.2075 | 100.00% |
| 2 | Education | 0.0298 | 14.34% |
| 3 | Site of onset | 0.0118 | 5.67% |
| 4 | Country | 0.0058 | 2.79% |
| 5 | Duration of coffee consumption | 0.0049 | 2.36% |
| 6 | Current alchool drinker | 0.0048 | 2.32% |
| 7 | Lifetime intensity of green tea consumption (cups/day) | 0.0016 | 0.78% |
| 8 | Gender | 0.0009 | 0.45% |
| 9 | BMI | 0.0008 | 0.37% |
| 10 | Lifetime intensity of coffee consumption (cups/day) | 0.0006 | 0.28% |
| 11 | Other types of tea load (cup-years) | 0.0003 | 0.16% |
| 12 | Duration of other tea consumption | 0.0001 | 0.06% |
| 13 | Lifetime intensity of other tea consumption (cups/day) | 0.0000 | 0.00% |
| 14 | Tea consumption status | 0.0000 | 0.00% |
| 15 | Green tea load (cup-years) | 0.0000 | 0.00% |
| 16 | Tea intensity at interview | 0.0000 | 0.00% |
| 17 | Duration of green tea consumption | 0.0000 | 0.00% |
| 18 | Coffee load (cup-years) | 0.0000 | 0.00% |
| 19 | Coffee consumption status | 0.0000 | 0.00% |
| 20 | Riluzole | 0.0000 | 0.00% |
| 21 | Current smokers | 0.0000 | 0.00% |
| 22 | Coffee intensity at interview | 0.0000 | 0.00% |
Variables are ranked from the most to the less important (rank).
VIMP is the sum of the decrease in prediction (of log-ΔFS) error values when a tree split by that variable whereas RVIMP is the VIMP divided by the highest VIMP value so that values are bounded between 0 and 1 (or between 0 and 100%).