This multi-center study analyzed age-related changes in vertebral CT attenuation values and established age-adjusted cutoffs for diagnosing osteoporosis. Researchers analyzed CT and dual-energy X-ray absorptiometry (DXA) data from 11,246 patients between 2022 and 2023. Using large-scale data, they calculated age-specific mean attenuation values and standard deviations to establish age-adjusted osteoporosis diagnostic thresholds. The results showed a consistent decline in attenuation values with aging in men, while women exhibited a sharp decrease after the age of 42. This decline was independent of the DXA T-score. In patients aged 65 and older, age-adjusted cutoffs outperformed unadjusted values (91.5% sensitivity when targeting 90% sensitivity and 90.0% specificity when targeting 90% specificity). Aview (Coreline Soft) was used to automatically identify and quantify attenuation values of the T11-L1 vertebrae from CT images, enhancing the reliability of quantitative analysis. A researcher from Coreline Soft contributed to the development of the AI-based automated analysis software used in this study.