Analysis of 29,266 UK Biobank cardiovascular patients revealed that declining kidney function strongly predicts Parkinson's disease risk, with impaired filtration rates showing dose-dependent associations (38-60% higher PD risk for chronic kidney disease). Most remarkably, kidney function trajectories began diverging from healthy controls over 14 years before Parkinson's diagnosis, suggesting a prolonged pre-clinical phase. The kidney-brain connection in cardiovascular patients represents a particularly high-risk convergence. These organs share similar vascular architectures and are both vulnerable to oxidative stress, inflammation, and protein misfolding - hallmarks of both kidney disease and neurodegeneration. The 14-year predictive window offers unprecedented opportunity for early intervention, though the optimal timing and methods remain unclear. For cardiovascular patients already managing multiple conditions, declining kidney function may serve as an early warning system for neurological risk. However, this preprint awaits peer review, and the observational design cannot establish causation. The findings could transform risk stratification in cardiology practices, where routine kidney monitoring might identify patients needing neuroprotective strategies years before symptoms emerge.