Bone Marrow Composition and Bone Microarchitecture and Turnover in Blacks and Whites

We examined the relationship between bone histomorphometric variables versus marrow cellularity, marrow adiposity (among hemopoietic cells), and fatty degeneration (areas of only fat) of bone marrow in iliac crest bone samples from 98 normal black (n = 53) and white (n = 45) males and females. We found blacks to have greater marrow cellularity (p = 0.0001), less marrow adiposity (among hemopoietic cells, p = 0.0001), greater values for bone volume (p = 0.030), trabecular thickness (p = 0.002), and static bone turnover variables (osteoid volume, p = 0.001; osteoid surface, p = 0.001; osteoid thickness, p = 0.001; eroded surface, p = 0.0006) than whites. Marrow cellularity correlated positively with static bone turnover variables osteoid volume (r = 0.257, p = 0.011), osteoid surface (r = 0.265, p = 0.008), osteoid thickness (r = 0.217, p = 0.032), and eroded surface (r = 0.273, p = 0.007) when all 98 cases were analyzed together. These findings suggest that marrow cells may influence bone turnover. The extent of fatty degeneration, but not that of adipose tissue, increased with age in blacks (r = 0.476, p = 0.0003) and whites (r = 0.476, p = 0.001), as did bone loss. There was no racial difference in the extent of fatty degeneration. We conclude that the lesser extent of adiposity in blacks is a racial characteristic that is unaffected by aging, whereas fatty degeneration which may have partly occupied space vacated by bone loss, is an aging phenomenon, unrelated to race. Greater bone turnover in blacks may be expected to lead to more frequent renewal of fatigue-damaged bone, which together with sturdier bone structure may contribute to the lower fragility fracture rates in blacks.