Emerging evidence identifies vascular aging independently predicting cardiovascular events, yet effective clinical interventions remain lacking. Nicotinamide adenine dinucleotide (NAD+) is an essential cofactor whose levels decline with age, and preclinical studies suggest that boosting NAD+ can improve vascular function and structure. Preliminary clinical studies in healthy older adults indicate that supplementation with NAD+ precursors, such as nicotinamide riboside(NR) or nicotinamide mononucleotide (NMN), can reduce arterial stiffness as measured by pulse wave velocity (PWV). However, whether NAD+ supplementation can improve vascular endothelial function and exert anti-stiffening effects in patients who have already developed measurable arterial stiffness remains unknown. Based on this evidence, the investigator hypothesize that the Coenzyme I for Injection will reverse vascular aging in older adults with established arterial stiffening.