Table 3.

Adjusted associations of verbal, performance, and full-scale intelligence quotient (VIQ, PIQ, and FSIQ) and metal biomarkers from multivariable linear regression models.

	VIQ	PIQ	FSIQ
	$\mathrm{\beta }$ (95% CI)	$\mathrm{\beta }$ (95% CI)	$\mathrm{\beta }$ (95% CI)
Biomarkera
ln-Hair manganese	$-1.4$ ($-3.2$, 0.4)	$-0.2$ ($-2.1$, 1.6)	$-0.9$ ($-2.7$, 0.9)
ln-Blood lead	$-0.04$ ($-1.8$, 1.7)	$-0.2$ ($-2.0$, 1.6)	$-0.1$ ($-1.8$, 1.6)
ln-Hair chromium	$-0.04$ ($-1.2$, 1.2)	0.5 ($-0.7$, 1.7)	0.3 ($-0.9$, 1.5)
ln-Hair copper by tertileb
Low	$-1.2$ ($-3.7$, 1.2)	0.2 ($-2.3$, 2.8)	$-0.7$ ($-3.1$, 1.7)
High	$-2.2$ ($-4.7$, 0.3)	$-1.0$ ($-3.5$, 1.6)	$-1.8$ ($-4.3$, 0.7)
ln-Hair manganese by copper tertile
Low	$-0.6$ ($-3.1$, 1.9)	$-0.5$ ($-3.1$, 2.0)	$-0.4$ ($-2.9$, 2.0)
High	2.5 (0.1, 4.9)	1.0 ($-1.5$, 3.4)	2.6 (0.2, 4.9)
ln-Blood lead by copper tertile
Low	$-2.1$ ($-4.6$, 0.3)	$-0.7$ ($-2.3$, 1.8)	$-1.5$ ($-3.9$, 1.0)
High	$-0.2$ ($-2.5$, 2.2)	0.1 ($-2.3$, 2.5)	$-0.3$ ($-2.7$, 2.0)

Note: Models were adjusted for sex, age, SES, hemoglobin, HOME score, and HOME score squared. Models are the following form: $\begin{array}{c}Y={\mathrm{\beta }}_0+{\mathrm{\beta }}_1\left(\text{ln\hspace{0.17em}}\mathrm{Mn}\right)+{\mathrm{\beta }}_2\left(\text{ln\hspace{0.17em}}\mathrm{Pb}\right)+{\mathrm{\beta }}_3\left(\text{low ln\hspace{0.17em}}\mathrm{Cu}\right)+{\mathrm{\beta }}_4\left(\text{high ln\hspace{0.17em}}\mathrm{Cu}\right)+\\ {\mathrm{\beta }}_5\left(\text{ln\hspace{0.17em}}\mathrm{Cr}\right)+{\mathrm{\beta }}_6\left(\text{ln\hspace{0.17em}}\mathrm{Mn}\times \text{low ln\hspace{0.17em}}\mathrm{Cu}\right)+{\mathrm{\beta }}_7\left(\text{ln\hspace{0.17em}}\mathrm{Mn}\times \text{high ln\hspace{0.17em}}\mathrm{Cu}\right)+{\mathrm{\beta }}_8\left(\text{ln\hspace{0.17em}}\mathrm{Pb}\times \text{low ln\hspace{0.17em}}\mathrm{Cu}\right)+{\mathrm{\beta }}_9\left(\text{ln\hspace{0.17em}}\mathrm{Pb}\times \text{high ln\hspace{0.17em}}\mathrm{Cu}\right)\end{array}$. CI, confidence interval; HOME, Home Observation Measurement of the Environment; SES, socioeconomic status.

^a$\mathrm{\beta }$ coefficients and 95% CIs averaged across 40 multiple imputed data sets. All metals concentrations were ln-transformed and standardized.

^bCu tertiles were created from ln-transformed variable; untransformed values of tertiles are $\text{low tertile}=1.72–7.83\mathrm{\mu }\mathrm{g}/\mathrm{g}$; $\text{middle tertile}=7.83–13.2\mathrm{\mu }\mathrm{g}/\mathrm{g}$; and $\text{high tertile}=13.2–191.0\mathrm{\mu }\mathrm{g}/\mathrm{g}$.