Table 3.
Zero-inflated Poisson regression models for the association between inattention, hyperactivity, and ADHD symptoms with ferritin levels (µg/L log scale) on a continuous scale and in tertiles.
| Tertile 1 [1.98, 20.92] (µg/L) | Tertile 2 (20.92, 38.79] (µg/L) | Tertile 3 (38.79, 216.5] (µg/L) | p for Trend ** | Continuous | ||
|---|---|---|---|---|---|---|
| Beta CI (95%) | Beta CI (95%) | Beta CI (95%) | Beta CI (95%) |
|||
| Inattention | ||||||
| Count model *1 | ||||||
| Male *** | 1 (Ref.) | −0.3 (−0.55, −0.05) | −0.37 (−0.6, −0.14) | 0.002 | −0.19 (−0.32, −0.07) | |
| Female *** | 1 (Ref.) | −0.11 (−0.64, 0.42) | 0.35 (−0.07, 0.77) | 0.066 | 0.09 (−0.13, 0.31) | |
| Zero-inflation model *2 | 1 (Ref.) | 0.19 (−0.24, 0.63) | 0.19 (−0.24, 0.63) | 0.488 | −0.04 (−0.26, 0.19) | |
| Hyperactivity | ||||||
| Count model *1 | 1 (Ref.) | −0.07 (−0.29, 0.16) | −0.11 (−0.33, 0.11) | 0.327 | −0.03 (−0.15, 0.09) | |
| Zero-inflation model *2 | 1 (Ref.) | 0.24 (−0.16, 0.64) | 0.17 (−0.23, 0.56) | 0.411 | 0.11 (−0.11, 0.32) | |
| ADHD | ||||||
| Count model *1 | 1 (Ref.) | −0.09 (−0.24, 0.06) | −0.09 (−0.23, 0.05) | 0.239 | −0.02 (−0.1, 0.05) | |
| Zero-inflation model *2 | 1 (Ref.) | 0.36 (0, 0.71) | 0.12 (−0.22, 0.47) | 0.515 | 0.13 (−0.06, 0.33) |
Models adjusted by cohort, smoking during pregnancy, alcohol intake during pregnancy, pre-pregnancy BMI, social class, sex and age of the child, living with mother/father, and weeks (week of sample collection). *1 Count model coefficients (Poisson with log link). *2 Zero-inflation model coefficients (binomial with logit link). ** p for the trend between tertiles. *** Model with interaction term between sex and ferritin. Significant associations (p < 0.05) are indicated in bold.