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. Author manuscript; available in PMC: 2011 Aug 1.
Published in final edited form as: Environ Res. 2010 Jun 20;110(6):595–603. doi: 10.1016/j.envres.2010.06.001

Table 3.

Coefficients From the Multilevel Model for Change of Height (SDSa) in Boys From Tapachula, Chiapas, Mexico 2002-2005 (n=788 boys, 2,633 observations)

Unadjusted β coefficientsb
 Adjusted β coefficientsc
Main effectd 95% CI Interactione 95% CI Main effectd 95% CI Interactione 95% CI
Interceptfg −0.031 −0.100, 0.039 0.012 0.007, 0.017 0.555 0.344, 0.766 0.014 −0.003, 0.030
p,p’-DDE
(μg/g)h
 ≤3.00 Reference Reference
 3.01-6.00 −0.124 −0.298, 0.049 0.018 0.005, 0.030 −0.121 −0.284, 0.042 0.019 0.006, 0.032
 6.01-9.00 −0.054 −0.306, 0.199 −0.008 −0.026, 0.010 −0.030 −0.267, 0.207 −0.005 −0.023, 0.013
 >9.00 −0.027 −0.235, 0.181 0.004 −0.011, 0.019 0.069 −0.131, 0.268 0.010 −0.006, 0.025
Smoked
during
pregnancyi 		0.554 −0.143, 1.250 −0.003 −0.055, 0.049 0.485 −0.165, 1.135 −0.006 −0.057, 0.045
Hospital of
recruitmenti
 Ministry of
 Health		 −0.462 −0.597, −0.326 −0.008 −0.018, 0.002 −0.280 −0.421, −0.139 −0.004 −0.014, 0.007
Rural
residence at
recruitmenti 		−0.198 −0.341, −0.055 −0.012 −0.023, −0.002 −0.052 −0.194, 0.090 −0.012 −0.023, −0.001
Gestational
age (wk)g 		0.059 −0.010, 0.129 0.004 −0.001, 0.009 0.041 −0.024, 0.105 0.003 −0.002, 0.008
Maternal
education
(years)
 None −1.018 −1.407, −0.630 −0.029 −0.057, −0.002 −0.507 −0.899, −0.115 −0.015 −0.044, 0.014
 1 - 6 −0.801 −1.041, −0.562 −0.008 −0.026, 0.010 −0.461 −0.708, −0.215 0.001 −0.018, 0.020
 7 - 9 −0.683 −0.921, −0.444 0.001 −0.017, 0.019 −0.471 −0.706, −0.236 0.006 −0.012, 0.024
 10 - 12 −0.404 −0.653, −0.155 −0.002 −0.021, 0.016 −0.330 −0.568, −0.093 0.000 −0.018, 0.018
 > 12 Reference Reference
Maternal
heightg 		0.051 0.040, 0.063 0.001 0.000, 0.002 0.040 0.029, 0.052 0.001 0.000, 0.002

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

a

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

b

Unadjusted 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

c

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

d

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

e

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

f

The intercept for the main effect term in the adjusted model represents the average height 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

g

Variables were median-centered as follow: age at measurements, 15.7 months; gestational age, 40 wk; maternal height, 152.5 cm

h

Determined from maternal serum samples drawn at delivery of the study child

i

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