**Background:** Biological aging estimation lacks a consensus reference variable. Ionizing radiation (IR) exposure shares mechanistic overlap with aging—including oxidative stress, inflammation, genomic instability, and cellular senescence—but limited data directly link IR to aging biomarkers like telomere length. This study aims to establish a genomics-based association between IR and aging using chronological age (CA) as a proxy for biological age, with the goal of providing a foundation for future biological age estimation and space radiation risk assessment.
**Methods:** Five publicly available GEO datasets (GSE20173, GSE21240, GSE23515, GSE42488, GSE53351) were used, all involving human blood samples exposed to gamma radiation. Two datasets (Data-A1: GSE42488, n=74; Data-A2: GSE53351, n=300) of healthy controls were combined to empirically determine an age cutoff between young and old using 12 aging-related genes (CDKN2A, FOXO1, SIRT1, IL6, TFAM, mTOR, TSC1, TP53, SIRT6, MLKL, ALOX15B, TNFAIP3). A for-loop tested each age from 21–65 as a cutoff, using t-tests and generalized linear models with AUC-ROC evaluation (1,000 permutations per cutoff). Two datasets with both age and radiation exposure (Data-B1: GSE21240, n=48; Data-B2: GSE23515, n=95) plus a radiation-only dataset (Data-R1: GSE20173, n=20) were combined for interaction testing. Linear models (gene ~ age * radiation) were run with age as both categorical (young/old) and continuous variables. Significant genes (p < 0.05) were used for preranked pathway and disease analysis via Ingenuity Pathway Analysis (IPA). Finally, 234 unique rad-age interaction genes were tested on a lung disease dataset (Data-D1: GSE42834, n=236) for differentiation across disease (control, pneumonia, TB, sarcoidosis, lung cancer), ethnicity, and sex using pairwise t-tests and linear models.
**Key Results:** An age cutoff of 29 years was empirically determined, with 5 of 12 aging genes significantly different and an average AUC of 0.672 at this threshold. Interaction models yielded 234 unique genes. Seventeen genes overlapped across multiple t-test comparisons, with 15 showing continued upregulation with increasing radiation exposure. Two genes (ASCC3 and SYNPO) showed expression changes with both age and radiation. IPA identified IL-1 signaling and PRPP biosynthesis as significant overlapping pathways. Common diseases included cancers of high-proliferating cells (digestive system cancers, non-melanoma tumors, head and neck tumors, breast cancer, carcinoma). From the 234 rad-age genes, 10 were significant in pairwise comparisons across train/test/validation sets of Data-D1. Three genes showed significant interactions: LAPTM4B was the only gene significant across disease, ethnicity, and sex (p = 0.004 for three-way interaction), with a fold change greater than 2. SRPK1 was significant with disease and sex, and ROM1 with disease only.
**Clinical Implications:** The study provides genomic evidence supporting an association between ionizing radiation exposure and aging processes, with inflammation (IL-1 signaling) and metabolism (PRPP biosynthesis) as key mechanistic links. The identification of LAPTM4B as a gene that differentiates lung diseases while accounting for ethnicity and sex suggests that rad-age genes may supplement disease risk assessment following radiation exposure. These findings could inform future biological age estimation methods and space radiation monitoring, though validation in larger, more diverse populations is needed before clinical application.