# Aging Alters Cervical Vertebral Bone Density Distribution: A Cross-Sectional Study
## 4 Results  
The ICCs for all of BMD parameters were higher than 0.997 for both intra- and inter-rater agreements (\(p<0.001\)) and those for the morphological parameters were higher than 0.763 (\(p<0.039\)).  
The C2 had significantly higher values of SD, volume, and height but significantly lower values of Mean, Low\({}_{5}\), and concavity than the C3 (\(p<0.014\)). The width of the C2 was measured significantly wider than the top of the C3 but significantly narrower than the bottom of the C3 (\(p<0.001\)). The value of High\({}_{5}\) was not significantly different between C2 and C3 (\(p=0.433\)). Most of values of the gray level and morphological parameters were significantly correlated between C2 and C3 (\(p<0.001\)) except concavity in male (\(p=0.116\)). In particular, the values of Mean and volume had strong positive correlations between C2 and C3 (r \(>0.837\), \(p<0.001\)) (Figure 3a,b).  
Figure 2: (**a**) Digital isolating process of C2 and C3 in 3D CBCT images for (**b**) the mid-sagittal CBCT slide views for (**c**) C2 and (**d**) C3 to measure (1) C2 height, (2) C2 width, (3) C2 concavity, (4) C3 top width, (5) C3 bottom width, (6) C3 anterior height, (7) C3 posterior height, and (8) C3 concavity. (**e**) Heterogeneity of gray levels, (**f**) a typical gray level histogram with gray level parameters, and (**g**) a comparison of the histograms between male and female. Male had higher voxel counts (i.e., volume) and female had higher gray levels (i.e., BMD parameters).  
The values of Mean and volume had significant positive correlations with most of other gray level and morphological parameters of C2 and C3 in both male and female, respectively (\(p<0.01\)).  
Figure 3: Correlations between C2 and C3 for (**a**) Mean gray level and (**b**) volume, and those of age with (**c**) C2 and (**d**) C3 Mean gray levels, and (**e**) C2 and (**f**) C3 volumes. The trend lines indicate a significant correlation (\(p<0.05\)). A significant interaction of sex on the correlation of volume between C2 and C3 (\(p=0.033\)) but not all other significant correlations (\(p>0.118\)).  
Most of the gray level parameters had significantly higher values of C2 and C3 in female than in male for all age groups (\(p\) < 0.039) except Mean and Low\({}_{5}\) values of C3 for 60-age group between male and female (\(p\) > 0.055) (Figures 2g, 3 and 4). On the other hand, most of the morphological parameters had significantly higher values of C2 and C3 in male than in female for all age groups (\(p\) < 0.035) except concavity of C2 for all age groups and C3 for 40- and 50-age groups between male and female (\(p\) > 0.131) (Figure 4).  
Age had significant negative correlations with the values of Mean, Low\({}_{5}\), and High\({}_{5}\) of C2 and C3 in both male and female (\(p\) < 0.05) (Figure 4c,d). Males had significant positive correlations of age with volume and width of C2 and C3 (\(p\) < 0.05) while females had a negative correlation with height of C2 (\(p\) = 0.04). The female 60-age group had significantly  
Figure 4: Comparisons between age groups of younger than 50 (40), 50s (50), and older than 50 (60) years in each female and male for (**a**) C2 and (**b**) C3 Mean gray levels, (**c**) C2 and (**d**) C3 Low5 gray levels, and (**e**) C2 and (**f**) C3 volumes. * \(p\) < 0.05.  
lower values of Mean and Low\({}_{5}\) of C2 and C3 than both the female 40- and 50-age groups (\(p<0.03\)) (Figure 4). The values of High\({}_{5}\) of C2 and C3 were significantly lower for the female 60-age group than the female 40-age group and both female 40- and 50-age groups, respectively (\(p<0.015\)). The values of these parameters were not significantly different between the female 40- and 50-age groups (\(p>0.34\)). The male 60-age group had significantly lower values of Low\({}_{5}\) and width of C2 and C3 than the male 40-age groups (\(p<0.05\)) (Figure 4). All other comparisons and correlations were not significant (\(p>0.05\)).