In this issue of Clinical Chemistry , Ellervik et al. (1) report relationships between baseline ferritin concentrations and risk of all-cause and cause-specific mortality in 8988 individuals enrolled in the Copenhagen City Heart Study. Median follow-up was 23 years, during which 6364 individuals died. Multifactorially adjusted hazard ratios for total mortality in individuals with ferritin values below vs above 200 μg/L showed significantly lower mortality overall ( P = 0.0008) and separately for men ( P = 0.02) and women ( P = 0.03) with lower ferritin concentrations. Cause-specific mortality below vs above the 200 μg/L threshold was significantly lower for cancer ( P = 0.005), metabolic disease ( P = 0.002) and cardiovascular disease ( P = 0.00006). A highly significant progressive decrease in median survival occurred with increasing ferritin concentrations. The hazard ratio for total mortality increased by 13% for each 100 μg/L increase in ferritin concentration. The median survival was 79 years with concentrations <200 μg/L, 76 years with ferritin concentrations between 200 and 399 μg/L, 72 years with ferritin concentrations between 400 and 599 μg/L, and 55 years with ferritin concentrations in excess of 600 μg/L. A stepwise increase in mortality with increasing ferritin concentrations was found for each disease category. Adjusted hazard ratios for increased disease-specific mortality for ferritin concentrations above 600 μg/L vs below 200 μg/L were significant for malignant ( P = 0.01), endocrine ( P = 0.0001), and cardiovascular ( P = 0.01) disease. The conclusion was that “increased ferritin concentrations represent a biological biomarker predictive of early death in a dose-dependent linear manner in the general population.” Increased ferritin concentrations were interpreted by the authors “as a biological marker of pathogenic processes that reflects severity and presence of a variety of disease states leading to premature death.” They stated that “causality may be …