Intervertebral T-score differences in younger and older women

The T-score discordance among skeletal sites is an important aspect of dual-energy X-ray absorptiometry (DXA) measurements. In the spine, large T-score differences between vertebrae are frequently seen in elderly patients owing to degenerative disease. However, it is unclear how often such differences occur in younger adults with healthy spines. The T-scores for individual lumbar vertebrae were compared for 2391 female singletons (18-79 yr) recruited to the Twins UK Adult Twin Register. Women were divided into 6 age bands and 5 bands by body weight, respectively, and the T-score differences between the pairs of vertebrae were examined using correlation coefficients and the standard error of the estimate (SEE) from linear regression analysis. Correlations between the T-scores for adjacent lumbar vertebrae were r = 0.92 decreasing to r = 0.79 between L1 and L4. When plotted as a function of age, r-values were constant for the 5 younger age bands, but decreased in the oldest group. In contrast, the T-score SEE values increased progressively with age from 0.4 to 0.5 for the younger groups to 0.7 for the oldest. Similar trends were seen when women were divided according to body weight. Both increasing age and higher body weight were statistically significantly associated with a higher T-score SEE. The incidence of large T-score differences between vertebrae varies with age and body weight, but is common even among younger women. Clinically significant T-score differences can occur in the absence of osteoarthritis, and visual assessment of spine DXA scans for evidence of degenerative disease is advised before vertebrae are omitted from scan analyses.