Table 5 Threshold effect analysis of serum estradiol level and sex hormone binding globulin level on lumbar bone mineral density using two-piecewise linear regression model
Lumbar bone mineral density | Adjusted β (95% CI), P value |
|---|---|
Serum estradiol level | |
Fitting by standard linear model | 0.65 (0.38, 0.93) < 0.001 |
Fitting by two-piecewise linear model | |
Inflection point | 70 (pg/mL) |
Serum estradiol level < 70 (pg/mL) | 1.92 (1.25, 2.59) |
Serum estradiol level > 70 (pg/mL) | − 0.24 (− 0.75, 0.27) |
Log likelihood ratio | < 0.001 |
Sex hormone binding globulin | |
Fitting by standard linear model | 0.01 (− 0.30, 0.31) 0.968 |
Fitting by two-piecewise linear model | |
Inflection point | 65 (nmol/L) |
Sex hormone binding globulin < 65 (nmol/L) | − 0.95 (− 1.80, − 0.09) 0.030 |
Sex hormone binding globulin > 65 (nmol/L) | 0.33 (− 0.08, 0.73) 0.115 |
Log likelihood ratio | 0.016 |