Biomarkers useful for diagnosing and assessing physiological age are provided, along with kits for measuring their expression. The invention also provides predictive models, based on the biomarkers, as well as computer systems, and software embodiments of the models for scoring and optionally classifying samples. In a preferred embodiment, the biomarkers include a group of biomarkers whose expression levels are highly correlated to each other. In a preferred embodiment, expression levels of CD248; CD248 and SLC 1A7; CD248 and one, two, three or four of the group consisting of CCR7, B3GAT1, VSIG4 and LRRN3; or CD248, SLC1A7 and one, two, three or four of the group consisting of CCR7, B3GAT1, VSIG4 and LRRN3 are determined.