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Table 1 Characteristics of the study sample according to diagnostic group (CHARGE study, n = 145)

From: Phthalate concentrations in house dust in relation to autism spectrum disorder and developmental delay in the CHildhood Autism Risks from Genetics and the Environment (CHARGE) study

Characteristics ASD (n = 50) DD (n = 27) TD (n = 68) p-values (ASD versus TD)a p-values (DD versus TD)a
  N % N % N %
Child gender        0.45 0.02
Male 40 80 17 63 58 85   
Female 10 20 10 37 10 15   
Child race        0.12 0.05
White, non-Hispanic 26 52 14 52 45 66   
Hispanic (any) 17 34 11 41 12 18   
Other 7 14 2 7 11 16   
Child age at dust collection (years)        0.03 0.12
<3 5 10 2 7 11 16   
3 to 4 10 20 6 22 26 38   
>4 35 70 18 67 31 46   
Missing 0 0 1 4 0 0   
Maternal education        0.42 0.04
High school diploma or lower, < 1 year college, technical vocational school 8 16 7 26 6 9   
>1 year college, associate degree 12 24 10 37 21 31   
Bachelor degree 20 40 7 26 29 43   
Graduate school 10 20 3 11 12 18   
Delivery payer        0.76 0.20
Government program/no insurance 5 10 6 22 8 12   
Private insurance 45 90 21 78 60 88   
Regional center catchment area at enrollment       0.88 0.50
Alta, Far Northern and Redwood Coast 26 52 20 74 39 57   
North Bay 9 18 3 11 13 19   
East Bay, San Andreas, and Golden Gate 6 12 2 7 7 10   
Valley Mt, Central Valley, and Kern 9 18 2 7 9 13   
Number of rooms with vinyl flooring        0.16 0.09
0 37 74 11 41 42 62   
≥1 13 26 15 56 26 38   
Missing 0 0 1 4 0 0   
Years of dust collection        0.02 0.38
2010 47 94 18 67 53 78   
2011 3 6 8 30 15 22   
Missing 0 0 1 4 0 0   
Continuous variables Mean SD Mean SD Mean SD   
Paternal age (years) 37 5.1 35 7 34 6 0.01 0.49
Maternal age (years) 34 4.7 33 6 32 6 0.06 0.78
Birth weight (g) 3456 715 2991 771 3402 557 0.48 0.01
Gestational duration (wks) 39 2.1 38 3 39 2 0.54 0.91
  1. ASD autism spectrum disorders, DD developmental delay, TD typically developing
  2. aChi-square test for categorical variables and Mann–Whitney test for continuous variables