Quantitative computed tomography of lumbar vertebrae in Japanese patients with osteoporosis.

Vertebral trabecular bone mineral density of both healthy Japanese subjects and Japanese patients with osteoporosis was measured by quantitative computed tomography (QCT) technique. The age-related reduction rate in vertebral trabecular bone mineral density of control females averaged 1.1% per year, from age 20 to 80, with an accelerated loss demonstrated after age 40. In the male controls, trabecular bone mineral density declined by an average of 0.9% per year. These values were found to be similar to the University of California at San Francisco (UCSF) QCT data (US Caucasians: 1.2% for female, 0.72% for male). Therefore, it appears that age-related rates of trabecular bone loss in the lumbar vertebrae may be similar for both Japanese and Caucasians. However, when compared to average values in UCSF QCT data of comparable age and sex, the mean values in Japanese appear to be approximately 10-20 mg/cm3 lower than Caucasian counterparts. All female patients with osteoporosis as evidenced by atraumatic vertebral fracture had QCT values below 50 mg/cm3. It is suggested that the Japanese may have lower trabecular bone mineral density than Caucasians but may also have a lower threshold for fracture of the vertebrae. Further studies are needed to establish the possible racial differences in vertebral trabecular bone mineral density, and to determine whether these possible disparities are related to genetic differences, or to differences in body size, dietary intake, physical activity or other lifestyle/environmental factors.