DNA methylation scores measuring coronary artery calcification and carotid plaque burden predicted cognitive decline, cardiovascular disease, and kidney dysfunction across two large cohorts of older adults (3,875 Americans and 487 Irish participants). Higher atherosclerosis scores correlated with 16% increased cardiovascular disease risk and significantly lower cognitive function, with carotid plaque markers specifically predicting incident dementia risk. These epigenetic signatures appear to capture cumulative vascular damage that extends beyond traditional risk factors, revealing how arterial aging systemically affects multiple organs including the brain and kidneys. The findings illuminate a crucial biological pathway connecting vascular health to cognitive longevity, suggesting that atherosclerotic processes detectable through DNA methylation patterns may serve as early warning systems for age-related decline. However, this preprint research awaits peer review, and the associations weakened after adjusting for socioeconomic factors, indicating complex interactions between biological and social determinants of aging. While the work represents an important step toward personalized vascular risk assessment, larger validation studies are needed to establish clinical utility of these methylation-based biomarkers for predicting healthy aging trajectories.