The NADage Study: Nicotinamide Riboside Replenishment Therapy Against Functional Decline in Aging

Inclusion Criteria: * Participant must understand the nature of the study and be able to provide written, informed consent. * Male or female aged ≥ 75 years at baseline. * Fried Frailty Phenotype score ≥ 3 to identify frail individuals. * Montreal Cognitive Assessment (MoCA) at screening adjusted to age, gender, and educational level, with a threshold set at the 10th percentile (z-score ≤ -1.28). Exclusion Criteria: * Inability to provide informed consent. * Does not reside in a facility or institution. * Advanced disability, end-stage disease, presence of severe chronic illness and/or life expectancy of less than a year. * Inability to complete a 6-minute walk test (6MWT) and/or contraindications to the procedure (history of unstable angina or myocardial infarction within 30 days prior to the test). * Diagnosis of active malignancy in the last 2 years at baseline (exceptions include non-metastatic skin conditions and non-metastatic and/or treated prostate cancer with stable prostate-specific antigen (PSA) levels in six months prior to baseline). Specific considerations may apply depending on the type of cancer. * Significant neurological or psychiatric disorders, including but not limited to psychotic disorders, severe bipolar or unipolar depression, multiple sclerosis, uncontrolled seizure conditions, and neurodegenerative disorder. * A history of cerebrovascular events, excluding transient ischemic attack (TIA) that occurs more than 3 months prior to baseline. * Hospitalization or major surgery within 3 months prior to baseline. * Significant changes in medications or treatment plans made less than one month prior to baseline, judged by the site investigator to interfere with the subject's participation in the study. * Consumption of NAD precursor supplements (e.g., Nicotinamide riboside, nicotinamide mononucleotide or Vitamin B3), or related supplements within 6 months prior to baseline. * Elective surgeries scheduled during the study duration. * Concurrent participation in other clinical trials with interventions that could affect frailty measures. * Any medical history, at the discretion of the investigator, might hinder compliance with study procedures or increase risk to the participant.