Heterogeneity in Lumbar Segmental Bone Mineral Density and Age-Related Evolution of Whole-Body Bone Mineral Density: Comprehensive Implications for Osteoporosis Risk Assessment

Objective: This study aimed to analyze the bone mineral density (BMD) in various body regions, establish reference data for whole-body BMD, investigate the effects of age and sex on BMD, and characterize BMD variations among different lumbar segments (L1-L4). Methods: BMD was measured using dual-energy X-ray absorptiometry (DXA). Patients were stratified to analyze the effects of age and sex on BMD at the following sites: lumbar spine (L1-L4); femur: Ward’s triangle, greater trochanter, femoral shaft, femoral neck, upper femoral neck, and lower femoral neck; radius: proximal and distal regions; ulnar: proximal and distal regions; and head, ribs, and pelvis. Subgroup analyses were conducted based on age, BMD Z-scores, BMD T-scores, and body mass index (BMI) to compare lumbar segmental BMD (L1-L4) between the sexes. The study included lumbar spine data from 20,199 patients; femur data from 23,218 patients; radius and ulna data from 466 patients; and head, ribs, and pelvis data from 1,288 patients. A whole-body BMD reference database was established to evaluate the age- and sex-related BMD trends and lumbar segmental heterogeneity. Results: In males, the BMD of lumbar segments L1-L4 showed an initial stabilization followed by a slight increase with age. The BMD at the femoral Ward’s triangle, femoral shaft, femoral neck (including the upper and lower regions), distal radius, and distal ulna began to decline from 45 to 49 years of age. The BMD of the femoral greater trochanter decreased at 50–54 years of age. The head BMD in males decreased at 55–59 years of age and stabilized at 65–69 years. The rib BMD showed no significant age-related changes, though the pelvic BMD decreased at 60­­–64 years. In females, the lumbar spine (L1-L4), femoral Ward’s triangle, ribs, and pelvis BMDs decreased with age, with the most rapid decline occurring in the 50–59-year age group. BMD reductions were also observed in the femoral neck (upper and lower regions), proximal and distal ulna, and proximal radius, with the greatest rate of decline at 55–64 years. The distal radius BMD decreased at 50–54 years, with the steepest decline at 55–64 years The head, femoral greater trochanter, and femoral shaft BMD decreased at 45 to 49 years of age, with the greatest reduction in the head BMD at 45–54 years. In male patients aged 50–89 years, the BMDs of L1 and L2 was significantly lower than those of L3 and L4 among different age groups. In female patients aged 40–89 years, the BMD of L1/L2 was significantly less than that of L3/L4 among different age groups. In male patients in the Z >-2.0 group, the BMD of L1/L2 was significantly lower than that of L3/L4. In female patients in the Z >-2.0 group, the BMD of L1/L2 was significantly lower than that of L3/L4. In the BMD T-score stratification groups, the BMD of L1/L2 was significantly lower than that of L3/L4 in both male and female patients. In male patients with a BMI <30 kg/m², the L1/L2 BMD was significantly lower than the L3/L4 BMD. In patients with a BMI ≥30 kg/m², the BMD of L1 was significantly lower than that of L3 and L4, the BMD of L2 was significantly lower than that of L4.The BMD of L1/L2 was significantly lower than that of L3/L4 in all female patients, regardless of BMI group. Conclusion: The BMDs of several body regions are associated with age and sex, with variations in rate of change, age at first change, and age-related trends depending on the anatomical site and sex. Heterogeneity exists among the lumbar segments, as the BMDs of L1 and L2 are generally significantly lower than those of L3 and L4; however, this trend varies in specific subgroups. Understanding site-specific BMD profiles may aid in predicting early fracture risk.