Table 2.

Correlation (R² values) explaining changes in BMC relative to plasma 25(OH)D, IGF-I, and 25(OH)D plus IGF-I in prepubertal females (n = 76) over a period of up to 9 yr

Skeletal site	25(OH)D + IGF-Ia	25(OH)Db	IGF-Ic	25(OH)D + FFSTd	IGF-I + FFSTe
Total body	0.837	0.809	0.874	0.947	0.953
Lumbar spine	0.718	0.698	0.759	0.925	0.932
Proximal femur	0.807	0.771	0.847	0.921	0.928
Forearm	0.780	0.759	0.812	0.921	0.927

Linear mixed models were employed to analyze the proportion of variance that 25(OH)D and IGF-I explained on BMC accrual at four skeletal sites. 

^aThe R² value depicts the pattern of change over time accounting for how growth in BMC might be influenced by both 25(OH)D and IGF-I. This model regressed BMC on age, age², baseline age, baseline age², natural log (log_e) of IGF-I, the interaction of log_eIGF-I and age, the interaction of log_eIGF-I and age², log_eIGF-I and baseline age, log_eIGF-I and baseline age², log_e25(OH)D (adjusted for season and race), the interaction of log_e25(OH)D and age, the interaction of log_e25(OH)D and age², log_e25(OH)D and baseline age, log_e25(OH)D and baseline age², and race. 

^bThe R² value depicts the pattern of change over time accounting for how growth in BMC might be influenced by 25(OH)D but not IGF-I. This model is the same as the 25(OH)D plus IGF-I model (2), except it excludes all terms involving IGF-I, capturing how bone mineral accrual depends on 25(OH)D. 

^cThe R² value depicts the pattern of change over time accounting for how growth in BMC might be influenced by IGF-I but not 25(OH)D. This model is the same as the 25(OH)D plus IGF-I model (2), except it excludes all terms involving 25(OH)D, capturing how bone mineral accrual depends on IGF-I. 

^dThe R² value depicts the partial association between BMC accrual and changes in 25(OH)D after controlling for FFST. 

^eThe R² value depicts the partial association between BMC accrual and changes in IGF-I after controlling for FFST.