Table 1.
Characteristics of children and their parents by ASD case status (266 matched pairs, n = 532 children)
| Variables | Categories | ASD case (n=266) N (%) | TD control (n=266) N (%) | Matched OR (95% CI) | P-Value* |
|---|---|---|---|---|---|
| Child’s sex | Male | 217 (81.6) | 217 (81.6) | N/A | 1.00 |
|
Child’s age (months) |
Age < 72 Age ≥ 72 |
185 (69.5) 81 (30.5) |
190 (71.4) 76 (28.6) |
0.44 (0.14, 1.44) | 0.18 |
| Child’s race | Afro-Caribbean | 254 (95.5) | 258 (97.0) | 1.50 (0.61, 3.67) | 0.37 |
|
Maternal age
a (at child’s birth) |
Age < 35 Age ≥ 35 |
215 (81.1) 50 (18.9) |
229 (87.7) 32 (12.3) |
0.58 (0.36, 0.94) | 0.03 |
|
Paternal age
b (at child’s birth) |
Age < 35 Age ≥ 35 |
141 (54.0) 120 (46.0) |
176 (69.0) 79 (31.0) |
0.48 (0.32, 0.71) | <0.01 |
| Maternal race | Afro-Caribbean | 256 (96.2) | 259 (97.4) | 1.43 (0.54, 3.75) | 0.47 |
| Paternal race c | Afro-Caribbean | 254 (95.9) | 255 (97.0) | 1.38 (0.55, 3.42) | 0.49 |
|
Maternal education
d (at child’s birth) |
Up to high school † Beyond high school†† |
137 (51.5) 129 (48.5) |
164 (62.4) 99 (37.6) |
0.69 (0.50, 0.95) | 0.02 |
|
Paternal education
e (at child’s birth) |
Up to high school † Beyond high school†† |
150 (58.6) 106 (41.4) |
195 (77.7) 56 (22.3) |
0.44 (0.29, 0.65) | <0.01 |
| Socioeconomic status (SES) | Car ownership | 150 (56.4) | 106 (39.9) | 0.50 (0.35, 0.72) | <0.01 |
| GSTP1 f | Ile/Ile Ile/Val Val/Val |
68 (25.9) 144 (54.8) 51 (19.4) |
65 (24.4) 139 (52.3) 62 (23.3) |
Reference 1.03 (0.67, 1.57) 1.30 (0.76, 2.22) |
0.58 |
| GSTM1 g | DD i I/I or I/Dj |
78 (29.7) 185 (70.3) |
62 (23.6) 201 (76.4) |
1.37 (0.93, 2.03) | 0.11 |
| GSTT1 h | DD i I/I or I/D j |
70 (26.6) 193 (73.4) |
65 (24.8) 197 (75.2) |
1.08 (0.74, 1.59) | 0.70 |
| Lead (Pb) (μg/dL) | Geometric mean k | 1.92 | 2.34 | - | <0.01** |
| Mercury (Hg) (μg/L) | Median l | 0.64 | 0.81 | - | 0.01*** |
| Arsenic (As) (μg/L) | Median l | 2.24 | 2.29 | - | 0.55 *** |
| Cadmium (Cd) (μg/L) | 75th percentile m | 0.20 | 0.20 | - | 1.00 *** |
| Aluminum (Al) (μg/L) n | Median l | 10.00 | 9.74 | - | 0.86 *** |
| Manganese (Mn) (μg/L) | Arithmetic mean o | 10.29 | 10.30 | - | 0.95 ** |
P-Values are based on Wald’s test in conditional logistic regression models.
We used univariable General Linear Models (GLM) and adjusted for pairs.
We used univariable quantile regression models and adjusted for pairs.
Up to high school education means attended Primary/Jr. Secondary, and Secondary/High/Technical schools.
Beyond high school education means attended a Vocational, Tertiary College, or University.
Maternal age was missing for 1 ASD case and 5 TD controls.
Paternal age was missing for 5 ASD cases and 11 TD controls.
Paternal race was missing for 1 ASD case and 3 TD controls.
Maternal education was missing for 3 TD controls.
Paternal education was missing for 10 ASD cases and 15 TD controls.
GSTP1 genotype was missing for 3 ASD cases.
GSTM1 genotype was missing for 3 ASD cases and 3 TD controls.
GSTT1 missing for 3 ASD cases and 4 TD controls.
DD indicates the null alleles for GSTT1 and GSTM1.
I/I or I/D indicate the homozygote (I/I) or a heterozygote (I/D) for GSTT1 and GSTM1.
Since the distribution of blood lead (Pb) concentrations were not normal for both ASD cases and TD controls, we reported geometric mean (Exp. [Mean (ln Pb concentration)]).
Median estimates are based on quantile regression.
We used quantile regression analysis at 75th percentile.
One concentration was missing for Al.
Since the distribution of blood manganese (Mn) concentrations was normal for both ASD cases and TD controls, we reported arithmetic means for Mn.