I used to be the newsletter coordinator for SDSI. While doing their newsletter, we had an Ask the Doctor section. The folowing comes from the SDSI Summer 2000 newsletter:
“ASK THE DOCTOR
Q: Can you explain what the normal cellularity of bone marrow is at various ages and how cellularity is determined?
A: Bone marrow cellularity decreases with age, by approximately 10% per decade. Thus, the marrow of a newborn infant is practically 100% cellular and that of a 50year old is approximately 50% cellular. Meaning the space is occupied by fat, which increases with age. These percents are obtained from bone marrow biopsies, by examination under the microscope and very roughly estimating how much of the area in the microscope field has cells compared to fat. THEY ARE VERY ROUGH FIGURES!
Blanche Alter, MD “