Table 4 Threshold effect analysis of serum calcium and 25(OH)D on total bone mineral density by using two-piecewise linear regression
From: Associations between serum calcium, 25(OH)D level and bone mineral density in adolescents
Adjusted ß (95% CI), p-value | |
|---|---|
Serum calcium | |
Total | |
Fitting by standard linear model | 0.0084 (0.0007, 0.0160) 0.0317 |
Fitting by two-piecewise linear model | |
Inflection point | 9.6 |
Serum calcium < 9.6 (mg/dL) | 0.0348 (0.0165, 0.0530) 0.0002 |
Serum calcium > 9.6 (mg/dL) | −0.0051 (− 0.0164, 0.0063) 0.3824 |
Log likelihood ratio | 0.002 |
Boy | |
Fitting by standard linear model | 0.0034 (−0.0076, 0.0143) 0.5446 |
Fitting by two-piecewise linear model | |
Inflection point | 9.6 |
Serum calcium < 9.6 (mg/dL) | 0.0447 (0.0128, 0.0765) 0.0060 |
Serum calcium > 9.6 (mg/dL) | −0.0109 (− 0.0260, 0.0042) 0.1564 |
Log likelihood ratio | 0.007 |
White | |
Fitting by standard linear model | 0.0129 (−0.0017, 0.0276) 0.0843 |
Fitting by two-piecewise linear model | |
Inflection point | 9.6 |
Serum calcium < 9.6 (mg/dL) | 0.0465 (0.0091, 0.0839) 0.0148 |
Serum calcium > 9.6 (mg/dL) | −0.0025 (− 0.0240, 0.0191) 0.8218 |
Log likelihood ratio | 0.055 |
Black | |
Fitting by standard linear model | 0.0053 (−0.0080, 0.0187) 0.4353 |
Fitting by two-piecewise linear model | |
Inflection point | 9.2 |
Serum calcium < 9.2 (mg/dL) | 0.1074 (0.0200, 0.1949) 0.0161 |
Serum calcium > 9.2 (mg/dL) | −0.0011 (− 0.0155, 0.0133) 0.8780 |
Log likelihood ratio | 0.020 |
Serum 25(OH)D | |
Boy | |
Fitting by standard linear model | 0.0013 (0.0009, 0.0018) < 0.0001 |
Fitting by two-piecewise linear model | |
Inflection point | 24 |
Serum 25(OH)D < 24(ng/mL) | 0.0024 (0.0015, 0.0034) < 0.0001 |
Serum 25(OH)D > 24(ng/mL) | 0.0007 (0.0000, 0.0014) 0.0400 |
Log likelihood ratio | 0.008 |
Girl | |
Fitting by standard linear model | 0.0003 (−0.0000, 0.0007) 0.0565 |
Fitting by two-piecewise linear model | |
Inflection point | 26 |
Serum 25(OH)D < 26(ng/mL) | 0.0011 (0.0005, 0.0018) 0.0006 |
Serum 25(OH)D > 26(ng/mL) | −0.0003 (− 0.0008, 0.0003) 0.3218 |
Log likelihood ratio | 0.004 |
White | |
Fitting by standard linear model | 0.0003 (−0.0002, 0.0009) 0.1945 |
Fitting by two-piecewise linear model | |
Inflection point | 23 |
Serum 25(OH)D < 23(ng/mL) | 0.0035 (0.0018, 0.0052) < 0.0001 |
Serum 25(OH)D > 23(ng/mL) | −0.0005 (− 0.0011, 0.0002) 0.1629 |
Log likelihood ratio | < 0.001 |