Sample sizes required to appropriately power RCTs of three years duration in patients with idiopathic PD
| Primary outcome measure | Event rate in control arm (%) | Relative risk reduction (%) | Absolute risk reduction (%) | Sample size in each study arm (80% power) | Sample size in each study arm (90% power) |
|---|---|---|---|---|---|
| PD-related mortality | 7.5 | 30 | 2.25 | 1938 | 2564 |
| All-cause mortality | 18.0 | 30 | 5.40 | 734 | 969 |
| H-Y stage ≥3 | 22.0 | 30 | 6.60 | 577 | 762 |
| S&E <80% | 28.5 | 30 | 8.55 | 417 | 549 |
| Dead or dependent (S&E <80%) | 38.4 | 30 | 11.52 | 277 | 364 |
| Dead or dependent (S&E <80%) | 38.4 | 20 | 7.68 | 627 | 830 |
| Dead or dependent (S&E <80%) | 20.0 | 20 | 4.00 | 1497 | 1987 |
| Dead or dependent (S&E ≤50%) | 22.6 | 30 | 6.78 | 559 | 737 |
Sample sizes were calculated with a 5% level of significance.
H-Y, Hoehn-Yahr scale; S&E, Schwab and England Activities of Daily Living Scale.