Table 4.

Coefficients From the Multilevel Model for Change of Body Mass Index (SDS^a) in Boys From Tapachula, Chiapas, Mexico 2002-2005 (n=787 boys, 2,632 observations)

	Unadjusted β coefficientsb				Adjusted β coefficientsc
	Main effectd	95% CI	Interactione	95% CI	Main effectd	95% CI	Interactione	95% CI
Interceptfg	0.046	−0.027, 0.119	−0.003	−0.010, 0.004	−0.017	−0.254, 0.219	0.021	0.000, 0.043
p,p’-DDE (μg/g)h
≤3.00	Reference				Reference
3.01-6.00	−0.059	−0.241, 0.123	−0.001	−0.017, 0.016	−0.112	−0.293, 0.070	−0.001	−0.017, 0.016
6.01-9.00	−0.168	−0.435, 0.099	0.023	−0.001, 0.047	−0.183	−0.447, 0.081	0.023	−0.001, 0.046
>9.00	0.116	−0.105, 0.338	−0.003	−0.023, 0.017	0.073	−0.152, 0.297	−0.002	−0.022, 0.018
Smoked during pregnancyi	0.811	0.055, 1.567	−0.074	−0.143, −0.006	0.750	0.006, 1.493	−0.066	−0.133, 0.002
Hospital of recruitmenti
Ministry of  Health	−0.100	−0.246, 0.045	−0.002	−0.015, 0.012	−0.042	−0.198, 0.115	0.003	−0.012, 0.017
Rural residence at recruitmenti	0.017	−0.134, 0.169	0.002	−0.012, 0.016	0.075	−0.084, 0.234	0.002	−0.013, 0.016
Gestational age (wk)g	0.016	−0.057, 0.089	−0.002	−0.009, 0.004	−0.007	−0.079, 0.066	−0.001	−0.007, 0.006
Maternal education (years)
None	−0.434	−0.851, −0.017	−0.003	−0.039, 0.034	−0.458	−0.885, −0.031	−0.007	−0.045, 0.031
1 - 6	−0.062	−0.318, 0.193	−0.032	−0.056, −0.009	−0.092	−0.358, 0.174	−0.036	−0.060, −0.011
7 - 9	−0.020	−0.274, 0.234	−0.027	−0.050, −0.004	−0.047	−0.304, 0.211	−0.028	−0.052, −0.005
10 - 12	0.251	−0.015, 0.516	−0.033	−0.057, −0.009	0.241	−0.021, 0.503	−0.035	−0.059, −0.011
> 12	Reference				Reference
Pre-pregnancy BMI (kg/m2)
≤18.5	−0.122	−0.396, 0.153	0.007	−0.019, 0.032	−0.075	−0.347, 0.198	0.004	−0.021, 0.030
18.6 - <25.0	Reference				Reference
25.0 − <30.0	0.127	−0.046, 0.300	0.000	−0.016, 0.016	0.157	−0.015, 0.328	0.000	−0.016, 0.016
≥30	0.465	0.221, 0.710	−0.003	−0.025, 0.019	0.487	0.245, 0.729	−0.001	−0.023, 0.020

Abbreviations: BMI, body mass index; CI, confidence interval; DDE, 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene; SDS, standard deviation scores

^aSDS, standard deviation scores internally derived at each age point as: measurement - population mean/population standard deviation. Height was missing for one observation and weight was missing for one subject

^bUnadjusted coefficients were obtained from models that also included a term for child’s age at measurements and subject-specific random intercepts and random slopes for age

^cAdjusted for all variables listed in the table (variables selected a priori)

^dMain effect term or initial status, represents the average difference in BMI SDS at 15.7 months of age (median age at first measurement) in a given category or value of a covariate

^eInteraction with child’s age at measurement (months), represents the average monthly rate of change in BMI SDS in a given category or value of a covariate

^fThe intercept for the main effect term in the adjusted model represents the average BMI SDS at the median age at the first measurement (15.7 months) for children in the lowest exposure group (DDE, ≤3.00 μg/g lipids) with reference values for the other covariates included in the model; and the interaction term for the intercept represents the average monthly rate of change in height SDS in the lowest exposure group (DDE, ≤3.00 μg/g lipids) with reference values for the other covariates included in the model

^gVariables were median-centered as follow: age at measurements, 15.7 mo; gestational age, 40 wk

^hDetermined from maternal serum samples drawn at delivery of the study child

ⁱReference groups were: smoked during pregnancy, No; hospital of recruitment, Social Security; residence at recruitment, Urban