Table 4.
The predicted minimum sample size per arm (for MRI and cognitive measures) (power = 0.0.8 and type 1 error = 0.05) for a hypothetical clinical trial of 3-year duration assuming a balanced design with measurements taken every year evenly in time to test hypothetical treatment effects of 30, 25, 20, 15, and 10% in the intervention group.
| Sample size (per arm) to test treatment effects of: |
||||
|---|---|---|---|---|
| Parameter | 30% | 25% | 20% | 15% |
| MRI measures | ||||
| WMH volume | 124 | 178 | 279 | 496 |
| Brain Volume | 145 | 208 | 325 | 578 |
| Lacunes | 572 | 842 | 1,345 | 2,442 |
| MD normalized peak height | 128 | 185 | 289 | 513 |
| Cognitive indices | ||||
| Executive function | 6,135 | 8,834 | 13,803 | 24,539 |
| Processing speed | 26,369 | 37,972 | 59,331 | 105,478 |
Abbreviations: MD, mean diffusivity; MRI, magnetic resonance imaging; WMH, white matter hyperintensity.