Table 4. Age-related changes in healthy bone composition (cortical and cancellous considered together).

Bone mineral densitya and tissue mineral densityb	Increase with age
Mineral to organic matrix ratioc	Increase with age
Calcium-to-phosphate ratiod	Increase with age
Carbonate-to-phosphate ratioc	Increase with age
Crystal size and perfection (crystallinity)c,e	Increase with age
Acid phosphate substitutionc	Decrease with age
Matrix heterogeneityb,c	Decrease with age
Total collagen crosslinks (collagen maturity)c	Increase with age
Collagen enzymatic crosslinksd	Increase with age
Collagen AGEsd	Increase with age

Abbreviations: AGE, advanced glycation end-products; BMDDD, bone mineral density distribution; DXA, dual photon absorptiometry; FTIRI, Fourier transform infrared microscopic imaging; XRD, X-ray diffraction.

^aDetermined by DXA,

^bDetermined by microcomputed tomography,

^cDetermined by FTIRI, BMDD and Raman spectroscopy,

^dDetermined by chemical analyses,

^eDetermined by XRD.