腰椎分節骨密度（BMD）の異質性と全身骨密度（BMD）の加齢に伴う変化：骨粗鬆症リスク評価への包括的示唆

This study aimed to analyze the bone mineral density (BMD) in various body regions, investigate the effects of age and sex on BMD, and characterize BMD variations among different lumbar segments (L1-L4). Thereby uncovering patterns of regional bone loss, quantifying heterogeneity risks, and dynamically tracking individual trajectories.

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; 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 conducted from 2019 to 2024 included lumbar spine data from 20,199 patients; femur data from 23,218 patients; and head, ribs, and pelvis data from 1288 patients.

In males, the BMD at the femoral Ward's triangle, femoral shaft, and femoral neck (including the upper and lower regions) 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. The rib BMD showed no significant age-related changes, though the pelvic BMD decreased at 60-64 years. In females, the head, femoral greater trochanter, and femoral shaft BMD decreased at 45-49 years of age. In male patients aged 50-89 years and female patients aged 40-89 years, male and female patients in the Z > -2.0 group, male and female patients in the BMD T-score stratification groups, male patients with a BMI < 30 kg/m², the BMDs of L1 and L2 were significantly lower than those of L3 and L4 among different age groups. The BMD of L1/L2 was significantly lower than that of L3/L4 in all female patients, regardless of BMI group.

The BMDs of several body regions are associated with age and sex, with variations in the 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.