This study investigates the longitudinal relationship between cognition and quantitative susceptibility mapping (QSM) in Parkinson's disease (PD). The research, conducted by a team from University College London, involved 59 PD patients and 22 controls over a 3-year period. Key findings include: 1. **Cognitive Severity**: Increased baseline susceptibility in the right temporal cortex, nucleus basalis of Meynert, and putamen was associated with greater cognitive severity after 3 years. Additionally, increased baseline susceptibility in the basal ganglia, substantia nigra, red nucleus, insular cortex, and dentate nucleus was linked to greater motor severity after 3 years. 2. **Motor Severity**: Increased follow-up susceptibility in these regions was associated with increased follow-up cognitive and motor severity, with further involvement of the hippocampus related to cognitive severity. 3. **Susceptibility Changes**: However, no consistent increases in susceptibility over the 3-year period were observed, suggesting that QSM may not be a reliable marker for tracking disease progression. 4. **Regional Analysis**: Post-hoc ROI analyses revealed significant negative associations between cognition and absolute susceptibility in the lateral orbitofrontal cortex, and positive associations in the insular cortex and lateral orbitofrontal cortex. 5. **Discussion**: The study suggests that QSM may predict cognitive and motor severity in PD many months before overt cognitive involvement, but robust longitudinal changes in QSM were not observed. Future research should combine imaging modalities to better understand tissue composition changes and clinical severity in PD. 6. **Limitations**: The study had limited power to detect differences between PD and control groups, and assessments of motor function were performed with participants in the ON state, which could affect cognitive performance. 7. **Conclusions**: The findings highlight the potential of QSM as a predictive tool for cognitive and motor severity in PD, but further research is needed to validate these findings and develop more robust methods for monitoring disease progression.This study investigates the longitudinal relationship between cognition and quantitative susceptibility mapping (QSM) in Parkinson's disease (PD). The research, conducted by a team from University College London, involved 59 PD patients and 22 controls over a 3-year period. Key findings include: 1. **Cognitive Severity**: Increased baseline susceptibility in the right temporal cortex, nucleus basalis of Meynert, and putamen was associated with greater cognitive severity after 3 years. Additionally, increased baseline susceptibility in the basal ganglia, substantia nigra, red nucleus, insular cortex, and dentate nucleus was linked to greater motor severity after 3 years. 2. **Motor Severity**: Increased follow-up susceptibility in these regions was associated with increased follow-up cognitive and motor severity, with further involvement of the hippocampus related to cognitive severity. 3. **Susceptibility Changes**: However, no consistent increases in susceptibility over the 3-year period were observed, suggesting that QSM may not be a reliable marker for tracking disease progression. 4. **Regional Analysis**: Post-hoc ROI analyses revealed significant negative associations between cognition and absolute susceptibility in the lateral orbitofrontal cortex, and positive associations in the insular cortex and lateral orbitofrontal cortex. 5. **Discussion**: The study suggests that QSM may predict cognitive and motor severity in PD many months before overt cognitive involvement, but robust longitudinal changes in QSM were not observed. Future research should combine imaging modalities to better understand tissue composition changes and clinical severity in PD. 6. **Limitations**: The study had limited power to detect differences between PD and control groups, and assessments of motor function were performed with participants in the ON state, which could affect cognitive performance. 7. **Conclusions**: The findings highlight the potential of QSM as a predictive tool for cognitive and motor severity in PD, but further research is needed to validate these findings and develop more robust methods for monitoring disease progression.