Investigation of age- and sex-related changes in cancellous bone density in the human spine using CT.

Studies of cancellous bone density across all spinal segments in relation to age and sex remain limited. This investigation aimed to quantify vertebral cancellous bone density in Hounsfield units (HU), to explore age‑ and sex‑related bone loss, and to compare HU measurements with bone mineral density (BMD) and bone volume fraction (BV/TV). Cancellous bone density was assessed in 71 spines (CT) covering vertebrae C3-L5 and the age range from 4 to 102 years. HU values were derived from mid‑vertebral regions, and in addition, BMD (L1-L3) and BV/TV measurements (Th12-L2, micro‑CT, 50 spines) in broad subsets of samples. The association between bone density and age was investigated by HU profiles along the spine in age groups and by regression approaches. HU values decreased with age (p < 0.001) and from cranial to caudal levels (p < 0.001), for both sexes (p < 0.001), with a marked reduction at the thoracolumbar junction beyond 60 years. Regression and cluster analyses revealed two phases of HU density loss with ongoing age, the second occurring in women (older than 64 years), later than in men (after 56 years) (p < 0.001). HU values were correlated with BMD (r = 0.86; 95% CI: 0.72-0.94) and with BV/TV (r = 0.51; 95% CI: 0.17-0.75). Density loss of bone with age is significant for BMD (for both sexes, p < 0.001) and for BV/TV (p ≤ 0.021), too, with an earlier reduction detected in the microarchitecture. These findings highlight the need for sex‑specific assessment and prevention strategies in osteoporosis research and clinical care.