The supplementary methods and results provide a detailed overview of the development and validation of a phenotypic age score based on DNA methylation (DNAm) data. The score was derived using a Cox penalized regression model applied to NHANES training data, selecting ten biomarkers, including chronological age, to predict 10-year mortality risk. This score was then converted into a phenotypic age estimate using a parametric proportional hazards model based on the Gompertz distribution. The method was validated using data from NHANES III and IV, as well as other cohorts such as the Women's Health Initiative (WHI), Framingham Heart Study (FHS), and Normative Aging Study (NAS). The DNAm PhenoAge score was found to be associated with various aging-related outcomes, including menopause age, breast cancer risk, dementia status, Down syndrome, HIV infection, and Parkinson's disease. It also showed significant differences between racial/ethnic groups and was negatively correlated with blood cell counts. The study also explored the relationship between DNAm PhenoAge and social, behavioral, and demographic factors, as well as its association with obesity and immunosenescence.The supplementary methods and results provide a detailed overview of the development and validation of a phenotypic age score based on DNA methylation (DNAm) data. The score was derived using a Cox penalized regression model applied to NHANES training data, selecting ten biomarkers, including chronological age, to predict 10-year mortality risk. This score was then converted into a phenotypic age estimate using a parametric proportional hazards model based on the Gompertz distribution. The method was validated using data from NHANES III and IV, as well as other cohorts such as the Women's Health Initiative (WHI), Framingham Heart Study (FHS), and Normative Aging Study (NAS). The DNAm PhenoAge score was found to be associated with various aging-related outcomes, including menopause age, breast cancer risk, dementia status, Down syndrome, HIV infection, and Parkinson's disease. It also showed significant differences between racial/ethnic groups and was negatively correlated with blood cell counts. The study also explored the relationship between DNAm PhenoAge and social, behavioral, and demographic factors, as well as its association with obesity and immunosenescence.