Table 1.

Percentage of ADHD cases and controls and geometric mean blood Pb, Hg, and Cd concentrations by maternal and child characteristics

Characteristics	Cases (n=71) %	Controls (n=58) %	Blood Pb (µg/dL)	Blood Total Hg (µg/L) Geometric mean	Blood Cd (µg/L)
Sex
Male	70	60	1.21	0.43	0.02
Female	30	40	1.52	0.38	0.02
Age groupb
5 to 8 years	39	45	1.67	0.40	0.02
9 to 12 years	61	55	1.10	0.42	0.02
Raceb
African American	39	38	1.56	0.41	0.02
Caucasian	61	62	1.17	0.41	0.02
Lead Investigation Areaa,b
Inside	38	71	1.65	0.42	0.02
Outside	62	29	1.01	0.41	0.02
Maternal smokinga
Yes	43	14	1.41	0.37	0.01
No	57	86	1.31	0.43	0.02
Maternal alcohol drinkinga
Yes	17	3	1.65	0.41	0.02
No	83	97	1.33	0.41	0.02
Socioeconomic statusa (mother paying for basic needs during pregnancy)
No difficulty	32	67	1.30	0.41	0.02
Slightly difficult	30	19	1.32	0.46	0.02
Moderate/Very difficult	38	14	1.39	0.39	0.01
Singleton
Yes	97	95	1.32	0.42	0.02
No	3	5	1.14	0.34	0.02
Low birth weight
Yes	11	13	1.21	0.37	0.02
No	89	87	1.33	0.40	0.02
Preterm birth
Yes	18	16	1.46	0.40	0.02
No	82	84	1.30	0.41	0.02
Breastfed
Yes	45	52	1.21	0.38	0.02
No	55	48	1.42	0.45	0.02
Postnatal Environmental Tobacco Smokea
Yes	47	24	1.24	0.40	0.02
No	53	76	1.41	0.41	0.02

^ap<0.05 between cases and controls

^bp<0.05 for blood Pb levels