Table 4.

Sex-stratified average predicted values of systolic blood pressure at percentiles of blood lead $\left(\overline{p}\left(y|x_q\right)\right)$, marginal difference in predicted systolic blood pressure per change in blood lead equivalent to 25 percentile change in the total population $\left(\overline{p}\left(y\mid x_{q1}\right)-\overline{p}\left(y\mid x_{q0}\right)\right.$, where exposure contrast from 50^th to 25^th percentile=0.47 ug/dL and 75^th to 50^thpercentile=0.78 ug/dL), and their model fit by analytic approach in NHANES 1999–2016 (n=23,113)^a

Model	Parameter	Females (n=11,180)	Males (n=11,933)
Linear	AIC	−145063	−157491
	$\overline{p}\left(y\mid x_{25}\right)$	115.64 (115.26, 116.01)	120.29 (119.94, 120.62)
	$\overline{p}\left(y\mid x_{50}\right)$	115.71 (115.37, 116.05)	120.36 (120.05, 120.66)
	$\overline{p}\left(y\mid x_{75}\right)$	115.82 (115.43, 116.23)	120.48 (120.19, 120.76)
	$\overline{p}\left(y\mid x_{50}\right)-\overline{p}\left(y\mid x_{25}\right)$	0.071 (−0.070, 0.23)	0.073 (0.0049, 0.15)
	$\overline{p}\left(y\mid x_{75}\right)-\overline{p}\left(y\mid x_{50}\right)$	0.11 (−0.11, 0.36)	0.12 (0.0077, 0.23)
Robust	AIC	−145052	−157473
	$\overline{p}\left(y\mid x_{25}\right)$	115.93 (115.56, 116.29)	120.68 (120.35, 120.98)
	$\overline{p}\left(y\mid x_{50}\right)$	116.01 (115.67, 116.34)	120.74 (120.45, 121.02)
	$\overline{p}\left(y\mid x_{75}\right)$	116.14 (115.75, 116.52)	120.85 (120.57, 121.12)
	$\overline{p}\left(y\mid x_{50}\right)-\overline{p}\left(y\mid x_{25}\right)$	0.082 (−0.053, 0.22)	0.068 (0.068, 0.13)
	$\overline{p}\left(y\mid x_{75}\right)-\overline{p}\left(y\mid x_{50}\right)$	0.13 (−0.085, 0.35)	0.11 (0.011, 0.2)
Log-transformed	AIC	−145061	−157501
	$\overline{p}\left(y\mid x_{25}\right)$	115.73 (115.35, 116.10)	119.90 (119.45, 120.33)
	$\overline{p}\left(y\mid x_{50}\right)$	115.73 (115.37, 116.08)	120.29 (119.98, 120.59)
	$\overline{p}\left(y\mid x_{75}\right)$	115.72 (115.25, 116.21)	120.68 (120.37, 120.99)
	$\overline{p}\left(y\mid x_{50}\right)-\overline{p}\left(y\mid x_{25}\right)$	−0.00078 (−0.25, 0.27)	0.39 (0.16, 0.62)
	$\overline{p}\left(y\mid x_{75}\right)-\overline{p}\left(y\mid x_{50}\right)$	−0.00078 (−0.25, 0.27)	0.39 (0.16, 0.63)
Quadratic	AIC	−145061	−157491
	$\overline{p}\left(y\mid x_{25}\right)$	115.61 (115.21, 115.99)	120.18 (119.73, 120.55)
	$\overline{p}\left(y\mid x_{50}\right)$	115.72 (115.37, 116.06)	120.30 (119.95, 120.61)
	$\overline{p}\left(y\mid x_{75}\right)$	115.87 (115.44, 116.34)	120.50 (120.21, 120.79)
	$\overline{p}\left(y\mid x_{50}\right)-\overline{p}\left(y\mid x_{25}\right)$	0.10 (−0.08, 0.33)	0.12 (0.016, 0.27)
	$\overline{p}\left(y\mid x_{75}\right)-\overline{p}\left(y\mid x_{50}\right)$	0.15 (−0.12, 0.49)	0.19 (0.026, 0.42)

Abbreviations: linear, general linear model (GLM) with untransformed X; robust, robust linear model with untransformed X; log-transformed, GLM with log-transformed X; quadratic, GLM with quadratic term for X; AIC, Akaike information criterion.

^aAdjusted for age, gender, race/ethnicity, education, NHANES cycle, waist circumference and 95% confidence intervals bootstrapped.