Table 3.
(a) Examination of NAPLAN associations with maternal urinary iodine concentration (UIC) as a continuous variable, n = 266 1. (b) NAPLAN mixed-effects multiple imputation using chained equations (MICE) 2 models: Differences in NAPLAN outcomes for offspring of mothers with deficient UIC (<150 μg/L) during pregnancy compared to mothers with sufficient UIC (≥150 μg/L), n = 266.
| NAPLAN | School Year of Test | (a) UIC Continuous | (b) UIC Categorical (<150 μg/L vs. ≥150 μg/L) | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| β Coefficient | p Value | n | Unadjusted | Adjusted for Biological Factors 3 | Adjusted for Biological & Socioeconomic Factors 4 | Adjusted for Biological & Socioeconomic Factors & Adolescent UIC 5 | ||||||
| β (95% CI) 6 | p Value | β (95% CI) | p Value | β (95% CI) | p Value | β (95% CI) | p Value | |||||
| Spelling | Year 3 | 0.043 | 0.011 | 248 | −43.6 (−65.9 to −21.4) | <0.0001 | −43.4 (−65.3 to −21.5) | <0.0001 | −44.4 (−66.2 to −22.5) | <0.001 | −41.4 (−65.1 to −17.6) | 0.001 |
| Year 5 | 0.040 | 0.002 | 252 | −34.1 (−56.2 to −11.9) | 0.003 | −34.1 (−55.8 to −12.4) | 0.002 | −35.0 (−56.6 to −13.4) | 0.002 | −31.9 (−55.4 to −8.4) | 0.008 | |
| Year 7 | 0.042 | 0.002 | 211 | −35.1 (−57.4 to −12.7) | 0.002 | −35.0 (−56.9 to −13.1) | 0.002 | −35.9 (−57.7 to −14.2) | 0.001 | −32.6 (−56.5 to −8.8) | 0.008 | |
| Year 9 | 0.037 | 0.005 | 194 | −33.5 (−56.8 to −10.1) | 0.005 | −33.6 (−56.5 to −10.7) | 0.004 | −34.8 (−57.6 to −12.0) | 0.003 | −31.6 (−57.0 to −6.2) | 0.015 | |
| Grammar | Year 3 | 0.027 | 0.150 | 248 | −24.2 (−47.7 to −0.7) | 0.043 | −23.3 (−46.4 to −0.3) | 0.047 | −24.2 (−47.2 to −1.3) | 0.039 | −26.2 (−50.0 to −2.3) | 0.031 |
| Year 5 | 0.035 | 0.015 | 252 | −28.3 (−51.6 to −5.0) | 0.017 | −26.9 (−49.8 to −4.0) | 0.021 | −28.0 (−50.8 to −5.2) | 0.016 | −29.6 (−53.5 to −5.7) | 0.015 | |
| Year 7 | 0.036 | 0.016 | 211 | −24.8 (−48.9 to −0.8) | 0.043 | −23.8 (−47.3 to −0.3) | 0.047 | −24.9 (−48.3 to −1.5) | 0.037 | −26.3 (−50.3 to −2.3) | 0.057 | |
| Year 9 | 0.032 | 0.003 | 194 | −13.8 (−37.7 to +10.1) | 0.256 | −13.1 (−36.8 to +10.6) | 0.278 | −13.9 (−37.3 to +9.6) | 0.246 | −15.7 (−40.2 to +8.9) | 0.211 | |
| Reading | Year 3 | 0.042 | 0.013 | 247 | −30.2 (−52.1 to −8.3) | 0.007 | −29.4 (−51.0 to −7.8) | 0.008 | −30.5 (−51.9 to −9.1) | 0.005 | −29.4 (−51.6 to −7.2) | 0.010 |
| Year 5 | 0.022 | 0.115 | 253 | −23.8 (−45.4 to −2.1) | 0.031 | −22.7 (−43.9 to −1.5) | 0.036 | −23.9 (−44.8 to −2.9) | 0.026 | −22.8 (−44.4 to −1.2) | 0.039 | |
| Year 7 | 0.031 | 0.018 | 207 | −14.0 (−36.8 to +8.7) | 0.226 | −13.2 (−35.5 to +9.1) | 0.246 | −14.2 (−36.3 to +7.8) | 0.205 | −13.2 (−35.6 to +9.2) | 0.249 | |
| Year 9 | 0.028 | 0.017 | 186 | −15.4 (−38.0 to +7.2) | 0.181 | −14.5 (−36.7 to +7.6) | 0.198 | −15.6 (−37.4 to +6.3) | 0.163 | −14.5 (−36.8 to +7.8) | 0.202 | |
| Writing | Year 3 | 0.017 | 0.216 | 245 | −11.2 (−32.2 to +9.9) | 0.297 | −7.6 (−27.7 to +12.5) | 0.459 | −8.3 (−28.4 to +11.7) | 0.415 | −9.5 (−30.6 to +11.6) | 0.377 |
| Year 5 | 0.029 | 0.016 | 251 | −25.5 (−46.1 to −4.9) | 0.015 | −22.1 (−41.9 to −2.3) | 0.029 | −22.9 (−42.6 to −3.1) | 0.023 | −24.0 (−44.9 to −3.2) | 0.024 | |
| Year 7 | 0.025 | 0.070 | 209 | −7.9 (−30.9 to +15.1) | 0.498 | −3.7 (−26.0 to +18.6) | 0.746 | −4.1 (−26.3 to +18.1) | 0.717 | −5.6 (−29.7 to +18.5) | 0.647 | |
| Year 9 | 0.030 | 0.036 | 193 | +1.2 (−23.4 to +25.7) | 0.927 | +4.0 (−19.7 to +27.6) | 0.741 | +3.5 (−20.2 to +27.2) | 0.772 | +2.1 (−22.4 to +26.5) | 0.869 | |
| Numeracy | Year 3 | 0.017 | 0.269 | 241 | −9.6 (−28.1 to +9.0) | 0.314 | −9.8 (−28.2 to +8.5) | 0.292 | −10.7 (−28.9 to +7.5) | 0.248 | −11.7 (−32.2 to +14.8) | 0.263 |
| Year 5 | 0.028 | 0.011 | 253 | −9.7 (−27.6 to +8.3) | 0.291 | −10.2 (−28.0 to +7.6) | 0.262 | −11.1 (−28.7 to +6.6) | 0.221 | −12.0 (−31.8 to +7.8) | 0.235 | |
| Year 7 | 0.022 | 0.041 | 207 | −12.3 (−30.4 to +5.8) | 0.183 | −12.7 (−30.6 to +5.1) | 0.163 | −13.6 (−31.4 to +4.2) | 0.133 | −14.6 (−34.3 to +5.2) | 0.149 | |
| Year 9 | 0.022 | 0.025 | 193 | −9.0 (−27.6 to +9.6) | 0.343 | −9.6 (−28.0 to +8.9) | 0.308 | −10.4 (−28.7 to +7.8) | 0.263 | −11.4 (−31.0 to +8.3) | 0.255 | |
1 Please note: Total numbers of children with specific NAPLAN outcomes always less than the n = 266 cohort total; n varies depending upon the number of children absent on each testing day. 2 Variables included in imputation model: regress (NAPLAN outcomes at each time point, birth weight, gestational length, adolescent UIC, Tasmanian State Government Student Assessment and Reporting Information scores for English and Maths in Years 2, 3 and 4, Australian Bureau of Statistics Socio-economic Indexes for Areas (scores): Index of Relative Socio-economic Advantage and Disadvantage, Index of Relative Socio-economic Disadvantage, Index of Economic Resources and, Index of Education and Occupation); ologit (paternal education); pmm (maternal education, low birth weight, preterm birth) and ; complete (maternal age at birth of child, sex of child, gestational age at time of maternal UI collection). 3 Adjusted for gestational age at the time of maternal UI collection, maternal age at birth of child, gestational length at time of birth, birth weight and sex. 4 Adjusted for all of the above and for maternal education. 5 Adjusted for all of the above and for adolescent UIC. 6 CI—Confidence Interval.