Osteoporosis is a growing global health challenge, with 1 in 6 men suffering fragility fractures after age 50. However, the effects of biological aging on the skeleton in men is poorly understood. Current fracture risk models fail to account for the biological ageing’s effect on the bones. This project aims to fill this gap by exploring how biological aging affect bone health and fracture risk in aging men. We propose three studies: (1) Using data from the DANCAVAs cohort of 14,973 men, we will develop advanced fracture risk models by combining bone density and biological aging markers. (2) We will follow men aged 50-65 with low bone mass to understand how biological aging impacts bone health over 4 years. (3) We will test rapamycin, a drug that may slow aging related bone loss, in men with low bone mass to evaluate how rapamycin influence bone loss in this population. This research will advance precision diagnostics and treatments, improving bone health and reducing fractures in aging men, with significant societal and international impact.