Table 3 Results of the analysis treating PFOS and PFOA concentrations as dimensional and categorical measures.

From: Umbilical cord serum concentrations of perfluorooctane sulfonate, perfluorooctanoic acid, and the body mass index changes from birth to 5 1/2 years of age

			Intercept		Interaction with age
			β (SE) p value		β (SE) p value
			crude	adjusted	crude	adjusted
Dimensional	PFOS
	Overall		− 0.27 (0.14) 0.05	− 0.35 (0.14) 0.01	0.0038 (0.002) 0.08	0.0038 (0.002) 0.09
	Boys		0.001 (0.18) > 0.99	− 0.095 (0.19) 0.62	0.0011 (0.003) 0.71	0.0011 (0.003) 0.72
	Girls		− 0.67 (0.2) 0.001	− 0.69 (0.2) 0.001	0.0081 (0.003) 0.015	0.0082 (0.003) 0.014
	PFOA
	Overall		− 0.22 (0.12) 0.07	− 0.26 (0.13) 0.05	0.0051 (0.002) 0.01	0.0051 (0.002) 0.01
	Boys		0.15 (0.18) 0.4	0.16 (0.19) 0.41	− 0.001 (0.003) 0.72	− 0.001 (0.003) 0.74
	Girls		− 0.59 (0.17) < 0.001	− 0.62 (0.18) < 0.001	0.011 (0.003) < 0.001	0.011 (0.003) < 0.001
Categorical	PFOS
	Overall	Low	0.00 (Reference)	0.00 (Reference)	0.00 (Reference)	0.00 (Reference)
		Middle	0.042 (0.071) 0.55	0.022 (0.07) 0.75	− 0.0001 (0.0012) 0.91	− 0.0001 (0.0012) 0.92
		High	− 0.16 (0.075) 0.03	− 0.175 (0.076) 0.02	0.0029 (0.0012) 0.02	0.0029 (0.0012) 0.02
	Boys	Low	0.00 (Reference)	0.00 (Reference)	0.00 (Reference)	0.00 (Reference)
		Middle	0.14 (0.10) 0.16	0.11 (0.1) 0.28	− 0.0022 (0.0017) 0.2	− 0.0022 (0.0017) 0.2
		High	− 0.021 (0.11) 0.84	− 0.03 (0.11) 0.75	0.0012 (0.0017) 0.49	0.0012 (0.0017) 0.49
	Girls	Low	0.00 (Reference)	0.00 (Reference)	0.00 (Reference)	0.00 (Reference)
		Middle	− 0.066 (0.096) 0.49	− 0.083 (0.094) 0.38	0.0019 (0.0016) 0.24	0.002 (0.0016) 0.23
		High	− 0.33 (0.10) 0.002	− 0.34 (0.11) 0.002	0.005 (0.0018) 0.005	0.005 (0.0018) 0.004
	PFOA
	Overall	Low	0.00 (Reference)	0.00 (Reference)	0.00 (Reference)	0.00 (Reference)
		Middle	− 0.091 (0.072) 0.21	− 0.069 (0.072) 0.34	0.0044 (0.0012) < 0.001	0.0044 (0.0012) < 0.001
		High	− 0.16 (0.074) 0.03	− 0.18 (0.078) 0.02	0.0038 (0.0012) 0.002	0.0039 (0.0012) 0.002
	Boys	Low	0.00 (Reference)	0.00 (Reference)	0.00 (Reference)	0.00 (Reference)
		Middle	0.0049 (0.10) 0.96	0.026 (0.1) 0.8	0.0029 (0.0017) 0.08	0.0029 (0.0017) 0.08
		High	0.044 (0.10) 0.67	0.03 (0.11) 0.79	0.0003 (0.0017) 0.88	0.0003 (0.0017) 0.86
	Girls	Low	0.00 (reference)	0.00 (Reference)	0.00 (Reference)	0.00 (Reference)
		Middle	− 0.19 (0.098) 0.06	− 0.17 (0.1) 0.1	0.0059 (0.0016) < 0.001	0.0059 (0.0016) < 0.001
		High	− 0.41 (0.1) < 0.001	− 0.41 (0.11) < 0.001	0.0078 (0.0017) < 0.001	0.0079 (0.0017) < 0.001

Controlling covariates: maternal age at delivery, maternal BMI before pregnancy, maternal education, household income, maternal smoking during pregnancy, parity, gestational age, and duration of breast feeding. NB: SE denotes standard error, PFOS denotes perfluorooctane sulfonate, PFOA denotes perfluorooctanoic acid.

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Table 3 Results of the analysis treating PFOS and PFOA concentrations as dimensional and categorical measures.

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