Summary of correlations between exposure measures and brain volumes
| Thalamus | Hippocampus | Caudate | Putamen | Amygdala | |
|---|---|---|---|---|---|
| Estimated reduction in volume for boxers relative to MMA fighters | 3.3% p=0.006 | 2.0% (L) and 4.2% (R)* p=0.007 | p=0.349 (NS) | 2.3% p=0.089 (NS) | 2.9% p=0.051 (NS) |
| Estimated reduction in volume per professional fight | 0.3% (L) and 0.4% (R) for boxers*; 0.2% (L) and 0.3% (R) for MMA* p=0.001*† | 0.1% (L) and 0.2% (R) for boxers*; 0.1% for MMA p=0.080† (NS) | 0.3% p=0.008 | p=0.516 (NS) | 0.2% p=0.076 (NS) |
| Estimated reduction in volume per year of professional fighting | 0.5% for boxers only p=0.050† (NS) | p=0.828 (NS) | 0.4% p=0.023 | p=0.750 (NS) | p=0.259 (NS) |
| Estimated reduction in volume for each unit increase in Exposure Composite Index | 0.8% p=0.042 | p=0.415 (NS) | 0.8% p=0.075 (NS) | p=0.665 (NS) | 0.9% p=0.052 (NS) |
Analysis adjusted for ICV, age, race and education. NS=not statistically significant at the 0.05 level.
*Statistically significant brain side effect (p<0.05).
†Statistically significant interaction between type of fighter and fight exposure variable.
ICV, intracranial volume; MMA, mixed martial arts.