A simple blood marker may help predict five-year survival in older adults, according to a study centered on red cell distribution width (RDW). RDW is derived from routine complete blood counts and reflects variability in circulating red blood cell size, making it an appealing candidate for low-cost prognostication. For geriatric oncology and primary care, the potential value is earlier risk signaling without requiring advanced imaging or complex assays. The clinical impact will depend on whether RDW improves accuracy beyond existing risk models and how consistently it performs across comorbidity profiles. Researchers will likely face scrutiny on confounders such as anemia, inflammation, nutritional deficiencies, and kidney function—factors that can also affect RDW and survival.