Table 4.
Zero-inflated Poisson regression models for the association between inattention, hyperactivity, and ADHD symptoms with ferritin levels (log scale).
| 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%) | |||
| stratified by Sex | ||||||
| Inattention | ||||||
| Boys | Count model *1 | 1 (Ref.) | −0.32 (−0.57, −0.06) | −0.4 (−0.63, −0.16) | 0.001 | −0.21 (−0.34, −0.08) |
| Zero-inflation model *2 | 1 (Ref.) | 0.09 (−0.46, 0.63) | −0.27 (−0.8, 0.25) | 0.270 | −0.14 (−0.43, 0.15) | |
| Girls | Count model *1 | 1 (Ref.) | 0.04 (−0.61, 0.69) | 0.58 (0.02, 1.13) | 0.012 | 0.15 (−0.09, 0.39) |
| Zero-inflation model *2 | 1 (Ref.) | 0.37 (−0.36, 1.09) | −0.32 (−1.13, 0.49) | 0.311 | −0.38 (−1.17, 0.42) | |
| Hyperactivity | ||||||
| Boys | Count model *1 | 1 (Ref.) | −0.09 (−0.37, 0.19) | −0.16 (−0.44, 0.11) | 0.244 | −0.03 (−0.18, 0.12) |
| Zero-inflation model *2 | 1 (Ref.) | 0.16 (−0.37, 0.68) | 0 (−0.52, 0.51) | 0.981 | −0.03 (−0.32, 0.25) | |
| Girls | Count model *1 | 1 (Ref.) | −0.02 (−0.44, 0.39) | −0.07 (−0.49, 0.35) | 0.727 | −0.1 (−0.33, 0.13) |
| Zero-inflation model *2 | 1 (Ref.) | 0.41 (−0.22, 1.04) | 0.48 (−0.16, 1.12) | 0.143 | 0.34 (−0.02, 0.7) | |
| ADHD | ||||||
| Boys | Count model *1 | 1 (Ref.) | −0.14 (−0.32, 0.03) | −0.22 (−0.39, −0.06) | 0.008 | −0.07 (−0.16, 0.02) |
| Zero-inflation model *2 | 1 (Ref.) | 0.25 (−0.23, 0.73) | −0.05 (−0.52, 0.41) | 0.778 | −0.02 (−0.27, 0.24) | |
| Girls | Count model *1 | 1 (Ref.) | 0.02 (−0.31, 0.34) | 0.17 (−0.13, 0.47) | 0.237 | 0.02 (−0.14, 0.19) |
| Zero-inflation model *2 | 1 (Ref.) | 0.6 (0.05, 1.16) | 0.49 (−0.05, 1.04) | 0.077 | 0.39 (0.08, 0.69) | |
| Stratified by Cohort | ||||||
| Inattention | ||||||
| Gipuzkoa | Count model *1 | 1 (Ref.) | −0.18 (−0.82, 0.47) | 0.18 (−0.35, 0.71) | 0.410 | 0.22 (−0.04, 0.48) |
| Zero-inflation model *2 | 1 (Ref.) | 0.8 (−0.15, 1.75) | 0.05 (−0.82, 0.91) | 0.873 | 0.16 (−0.31, 0.63) | |
| Sabadell | Count model *1 | 1 (Ref.) | −0.35 (−0.72, 0.03) | −0.22 (−0.55, 0.1) | 0.116 | −0.16 (−0.31, 0) |
| Zero-inflation model *2 | 1 (Ref.) | 0.38 (−0.29, 1.05) | 0.03 (−0.6, 0.66) | 0.887 | −0.03 (−0.36, 0.3) | |
| Valencia | Count model *1 | 1 (Ref.) | −0.24 (−0.64, 0.15) | −0.39 (−0.76, −0.02) | 0.043 | −0.29 (−0.51, −0.06) |
| Zero-inflation model *2 | 1 (Ref.) | −0.44 (−1.22, 0.35) | −0.6 (−1.35, 0.14) | 0.123 | −0.27 (−0.71, 0.18) | |
| Hyperactivity | ||||||
| Gipuzkoa | Count model *1 | 1 (Ref.) | −0.07 (−0.77, 0.62) | 0.06 (−0.67, 0.78) | 0.932 | 0.23 (−0.11, 0.57) |
| Zero-inflation model *2 | 1 (Ref.) | 0.65 (−0.3, 1.6) | −0.1 (−1, 0.8) | 0.838 | 0.1 (−0.4, 0.59) | |
| Sabadell | Count model *1 | 1 (Ref.) | −0.25 (−0.6, 0.11) | −0.31 (−0.64, 0.02) | 0.053 | −0.12 (−0.28, 0.03) |
| Zero-inflation model *2 | 1 (Ref.) | 0.24 (−0.36, 0.85) | −0.09 (−0.69, 0.51) | 0.814 | −0.04 (−0.35, 0.27) | |
| Valencia | Count model *1 | 1 (Ref.) | 0.06 (−0.36, 0.48) | 0.06 (−0.36, 0.48) | 0.904 | 0.01 (−0.25, 0.27) |
| Zero-inflation model *2 | 1 (Ref.) | −0.02 (−0.87, 0.82) | 0.59 (−0.17, 1.36) | 0.070 | 0.4 (−0.03, 0.82) | |
| ADHD | ||||||
| Gipuzkoa | Count model *1 | 1 (Ref.) | −0.06 (−0.48, 0.36) | 0.37 (−0.01, 0.74) | 0.045 | 0.33 (0.14, 0.53) |
| Zero-inflation model *2 | 1 (Ref.) | 0.85 (0.06, 1.63) | 0.27 (−0.48, 1.02) | 0.412 | 0.28 (−0.13, 0.69) | |
| Sabadell | Count model *1 | 1 (Ref.) | −0.29 (−0.53, −0.06) | −0.28 (−0.5, −0.07) | 0.005 | −0.1 (−0.21, 0) |
| Zero-inflation model *2 | 1 (Ref.) | 0.39 (−0.14, 0.92) | 0.03 (−0.49, 0.55) | 0.857 | 0.08 (−0.19, 0.35) | |
| Valencia | Count model *1 | 1 (Ref.) | 0.09 (−0.16, 0.35) | −0.11 (−0.35, 0.14) | 0.244 | −0.07 (−0.21, 0.08) |
| Zero-inflation model *2 | 1 (Ref.) | −0.04 (−0.68, 0.6) | 0.07 (−0.55, 0.69) | 0.788 | 0.12 (−0.24, 0.49) | |
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). For Gipuzkoa and Sabadell, models do not include the variable “lives with mother/father”. *1 Count model coefficients (Poisson with log link). *2 Zero-inflation model coefficients (binomial with logit link). ** p for the trend between tertiles. Significant associations (p < 0.05) are indicated in bold.