Models of spinal trabecular bone loss as determined by quantitative computed tomography

Noninvasive bone densitometry techniques have significantly improved our understanding of the pattern and magnitude of bone loss over the life span. Quantitative computed tomography (QCT) is capable of selectively measuring highly labile trabecular bone in the central portion of the vertebrae. Trabecular bone mineral density (mg/ml) was determined in 538 healthy women ranging in age from 20 to 80 using GE CT/T scanners at 80 kVp. Various statistical regressions were performed for the entire population to describe the general pattern of bone loss from the spine; a cubic model (r = ‐0.69, SEE = 26.0 mg/ml) was found to be statistically superior (p < 0.01) to linear, quadratic, or exponential models. An average bone loss was approximated from these regression analyses with a yearly absolute rate of ‐2.02 ± 0.097 mg/ml per year (p < 0.0001). The average rate of change for premenopausal women was ‐0.45 mg/ml per year (p < 0.05), for perimenopausal women was ‐4.39 mg/ml per year (p < 0.0001) and for postmenopausal women was ‐1.99 mg/ml per year (p < 0.0001). QCT values were also stratified into 5 and 10 year age groups and analyzed seperately for pre‐ and postmenopausal women. The 5 and 10 year interval stratification revealed no identifiable bone density decrements prior to midlife using analysis of variance statistical methods; significant losses of bone mineral density were noted to correspond with the usual time of menopause and to continue into old age. Various two‐phase regressions were employed using age and menstrual status to improve the description of age‐ and menopause‐related bone loss. For all women, a linear‐exponential pattern (r = ‐0.70, SEE = 25.44 mg/ml) with a decrement of 25 mg/ml across the early menopause, appeared most plausible, amounting to an average bone loss of 60% over the life span. We provide normative data here on spinal trabecular bone density appropriate for clinical comparison of female subjects encompassing the adult age range and menopausal status.