Association between serum estradiol level and appendicular lean mass index in middle-aged postmenopausal women

Table 1 Weighted characteristics of study population based on serum estradiol level quartiles

Serum estradiol level (pg/mL)	Q1 (≤ 3.80)	Q2 (3.88-7.42)	Q3 (7.45-17.50)	Q4 (≥ 17.60)	P value
Age (yr)	54.4 ± 4.1	53.6 ± 4.0	52.9 ± 4.8	49.6 ± 4.9	< 0.001
Race/Ethnicity (%)					0.584
Non-Hispanic White	70.9	68.3	70.1	73.6
Non-Hispanic Black	7.8	14.1	10.9	10.4
Mexican American	6.1	8.3	8.3	6.3
Other race/ethnicity	15.2	9.3	10.7	9.7
Education level (%)					0.520
Less than high school	13.3	14.1	12.7	10.1
High school	24.5	19.2	24.9	19.0
More than high school	62.2	66.6	62.3	71.0
Body mass index (kg/m2)	25.6 ± 4.7	28.8 ± 4.8	32.2 ± 5.9	32.0 ± 8.3	< 0.001
Income to poverty ratio	3.0 ± 1.8	3.3 ± 1.7	3.1 ± 1.5	3.4 ± 1.6	0.143
Moderate activities (%)					0.965
Yes	49.1	47.2	49.7	49.8
No	50.9	52.8	50.3	50.2
Total protein (g/L)	69.9 ± 4.6	70.5 ± 4.1	71.1 ± 4.0	70.0 ± 3.4	0.022
Blood urea nitrogen (mg/dL)	5.0 ± 1.6	4.8 ± 1.6	4.8 ± 1.8	4.6 ± 1.2	0.076
Serum uric acid (umol/L)	263.8 ± 57.0	287.1 ± 69.7	302.9 ± 68.2	286.6 ± 67.6	< 0.001
Serum calcium (mg/dL)	2.4 ± 0.1	2.4 ± 0.1	2.4 ± 0.1	2.3 ± 0.1	0.092
Appendicular lean mass index (kg/m2)	6.1 ± 1.0	6.8 ± 1.0	7.3 ± 1.1	7.5 ± 1.4	< 0.001

mean ± SD for continuous variables: P value was calculated by weighted linear regression model. “%” for categorical variables: P value was calculated by weighted chi-square test.

Table 2 Association between serum estradiol level (pg/mL) and appendicular lean mass index (kg/m²)

	Model 1 β (95%CI)	Model 2 β (95%CI)	Model 3 β (95%CI)
Serum estradiol level	0.004 (0.002, 0.007)a	0.003 (0.001, 0.005)a	0.001 (0.000, 0.002)b
Serum estradiol level categories
Q1	Reference	Reference	Reference
Q2	0.665 (0.406, 0.924)	0.607 (0.356, 0.859)	0.090 (-0.036, 0.216)
Q3	1.222 (0.969, 1.475)	1.199 (0.953, 1.445)	0.128 (-0.002, 0.258)
Q4	1.369 (1.126, 1.612)	1.385 (1.133, 1.637)	0.268 (0.133, 0.402)
P value	< 0.001	< 0.001	< 0.001

^aP < 0.001.

^bP < 0.01.

Model 1: No covariates were adjusted. Model 2: Age and race were adjusted. Model 3: Age, race, educational level, body mass index, ratio of family income to poverty, moderate activities, total protein, blood urea nitrogen, serum uric acid, and serum calcium were adjusted.

Table 3 Association between serum estradiol level (pg/mL) and appendicular lean mass index (kg/m²), stratified by body mass index and race

	Model 1 β (95%CI)	Model 2 β (95%CI)	Model 3 β (95%CI)
Stratified by BMI
BMI (< 25 kg/m2)	0.002 (-0.000, 0.004)	0.001 (-0.001, 0.004)	0.002 (0.000, 0.003)a
BMI (25-29.9 kg/m2)	0.003 (0.001, 0.005)b	0.002 (0.000, 0.004)a	0.001 (-0.001, 0.003)
BMI (≥ 30 kg/m2)	0.006 (0.004, 0.009)c	0.005 (0.002, 0.008)a	0.001 (-0.001, 0.003)
Stratified by race
Non-Hispanic White	0.003 (-0.000, 0.007)	0.002 (-0.002, 0.006)	0.002 (-0.000, 0.004)
Non-Hispanic Black	0.004 (0.000, 0.007)a	0.004 (-0.000, 0.007)	0.001 (-0.000, 0.003)
Mexican American	0.003 (-0.002, 0.008)	0.003 (-0.002, 0.008)	-0.003 (-0.005, 0.000)
Other race	0.015 (0.009, 0.022)c	0.013 (0.007, 0.020)c	0.002 (-0.001, 0.006)

^aP < 0.05.

^bP < 0.01.

^cP < 0.001.

Model 1: No covariates were adjusted. Model 2: Age, and race were adjusted. Model 3: Age, race, educational level, body mass index, ratio of family income to poverty, moderate activities, total protein, blood urea nitrogen, serum uric acid, and serum calcium were adjusted. BMI: Body mass index.

Table 4 Threshold effect analysis of serum estradiol level on appendicular lean mass index using two-piecewise linear regression model

Appendicular lean mass index	Adjusted β (95%CI), P value
Serum estradiol level
Fitting by standard linear model	0.001 (0.000, 0.002), 0.006
Fitting by two-piecewise linear model
Inflection point	85 (pg/mL)
Serum estradiol level < 85 (pg/mL)	0.004 (0.002, 0.007), < 0.001
Serum estradiol level > 85 (pg/mL)	-0.001 (-0.003, 0.001), 0.280
Log likelihood ratio	0.003

Age, race, educational level, body mass index, ratio of family income to poverty, moderate activities, total protein, blood urea nitrogen, serum uric acid, and serum calcium were adjusted.